... every chemical combination is wholly and solely dependent on two opposing forces, positive and negative electricity, and every chemical compound must be composed of two parts combined by the agency of their electrochemical reaction, since there is no third force. Hence it follows that every compound body, whatever the number of its constituents, can be divided into two parts, one of which is positively and the other negatively electrical.

… man-midwifery, with other “indecencies,” is a great system of fashionable prostitution; a primary school of infamy—as the fashionable hotel and parlor wine glass qualify candidates for the two-penny grog-shop and the gutter.

...[T]he natural history of the rat is tragically similar to that of man ... some of the more obvious qualities in which rats resemble men — ferocity, omnivorousness, and adaptability to all climates ... the irresponsible fecundity with which both species breed at all seasons of the year with a heedlessness of consequences, which subjects them to wholesale disaster on the inevitable, occasional failure of the food supply.... [G]radually, these two have spread across the earth, keeping pace with each other and unable to destroy each other, though continually hostile. They have wandered from East to West, driven by their physical needs, and — unlike any other species of living things — have made war upon their own kind. The gradual, relentless, progressive extermination of the black rat by the brown has no parallel in nature so close as that of the similar extermination of one race of man by another...

…I distinguish two parts of it, which I call respectively the brighter and the darker. The brighter seems to surround and pervade the whole hemisphere; but the darker part, like a sort of cloud, discolours the Moon’s surface and makes it appear covered with spots. Now these spots, as they are somewhat dark and of considerable size, are plain to everyone and every age has seen them, wherefore I will call them great or ancient spots, to distinguish them from other spots, smaller in size, but so thickly scattered that they sprinkle the whole surface of the Moon, but especially the brighter portion of it. These spots have never been observed by anyone before me; and from my observations of them, often repeated, I have been led to the opinion which I have expressed, namely, that I feel sure that the surface of the Moon is not perfectly smooth, free from inequalities and exactly spherical… but that, on the contrary, it is full of inequalities, uneven, full of hollows and protuberances, just like the surface of the Earth itself, which is varied everywhere by lofty mountains and deep valleys.

…winds are produced by differences of air temperature, and hence density, between two regions of earth.

“If there are two theories, one simpler man the other, the simpler one is to be preferred.” At first sight this does not seem quite so bad, but a little thought shows that our tendency to prefer the simpler possibility is psychological rather than scientific. It is less trouble to think that way. Experience invariably shows that the more correct a theory becomes, the more complex does it seem. … So this … interpretation of [Ockham’s Razor] is … worthless.

“One and one make two” assumes that the changes in the shift of circumstance are unimportant. But it is impossible for us to analyze this notion of unimportant change.

“Unless,” said I [Socrates], “either philosophers become kings in our states or those whom we now call our kings and rulers take to the pursuit of' philosophy seriously and adequately, and there is a conjunction of these two things, political power and philosophic intelligence, while the motley horde of the natures who at present pursue either apart from the other are compulsorily excluded, there can be no cessation of troubles, dear Glaucon, for our states, nor, I fancy for the human race either. Nor, until this happens, will this constitution which we have been expounding in theory ever be put into practice within the limits of possibility and see the light of the sun.”

“Yes,” he said. “But these things (the solutions to problems in solid geometry such as the duplication of the cube) do not seem to have been discovered yet.” “There are two reasons for this,” I said. “Because no city holds these things in honour, they are investigated in a feeble way, since they are difficult; and the investigators need an overseer, since they will not find the solutions without one. First, it is hard to get such an overseer, and second, even if one did, as things are now those who investigate these things would not obey him, because of their arrogance. If however a whole city, which did hold these things in honour, were to oversee them communally, the investigators would be obedient, and when these problems were investigated continually and with eagerness, their solutions would become apparent.”

[1665-04-30] ...Great fear of the sicknesses here in the City, it being said that two or three houses are already shut up. God preserve us all.

[1665-06-07] ...This day, much against my will, I did in Drury Lane see two or three houses marked with a red cross upon the doors, and 'Lord have mercy upon us' writ there - which was a sad sight to me, being the first of that kind that to my remembrance I ever saw. It put me into an ill conception of myself and my smell, so that I was forced to buy some roll-tobacco to smell to and chaw - which took away the apprehension.

[1665-07-22] I met this noon with Dr Burnett, who told me ... that his servant died of a Bubo on his right groine, and two Spots on his right thigh, which is the plague.

[1665-08-16] ...Hence to the Exchange, which I have not been a great while. But Lord, how sad a sight it is to see the streets empty of people, and very few upon the Change - jealous of every door that one sees shut up, lest it should be the plague - and about us, two shops in three, if not more, generally shut up. ... It was dark before I could get home; and so land at church-yard stairs, where to my great trouble I met a dead Corps, of the plague, in the narrow ally, just bringing down a little pair of stairs - but I thank God I was not much disturbed at it. However, I shall beware of being late abroad again.

[A contemporary study] predicted the loss of two-thirds of all tropical forests by the turn of the century. Hundreds of thousands of species will perish, and this reduction of 10 to 20 percent of the earth’s biota will occur in about half a human life span. … This reduction of the biological diversity of the planet is the most basic issue of our time.

[About the mechanical properties of the molecules of a chemical substance being studied:] They could be measured, but that would have taken several months. So someone said, ‘Let’s get Teller in and make him guess the data.’ We got him into a room and locked the door, so no one else could get at him, and he asked questions and did some figuring at the blackboard. He got the answers in about two hours, not entirely accurately, of course, but—as we found out when we got around to verifying them—close enough for the purpose.

[At the end of the story, its main character, Tom] is now a great man of science, and can plan railroads, and steam-engines, and electric telegraphs, and rifled guns, and so forth; and knows everything about everything, except why a hen's egg don't turn into a crocodile, and two or three other little things that no one will know till the coming of the Cocqcigrues.

[Blackett] came one morning, deep in thought, into the G (technical) Office at Stanmore. It was a bitterly cold day, and the staff were shivering in a garret warmed over only with an oil-stove. Without a word of greeting, Blackett stepped silently up on to the table and stood there pondering with his feet among the plans. After ten minutes somebody coughed uneasily and said, diffidently: “Wouldn’t you like a chair, sir … or something?” “No, thank you,” said Professor Blackett, “it is necessary to apply scientific methods. Hot air rises. The warmest spot in this room, therefore, will be near the ceiling.” At this, Colonel Krohn, my technical G.S.O., stepped up on the table beside the Professor, and for the next half-hour, the two stayed there in silence. At the end of this period Professor Blackett stepped down from the table saying: “Well! That’s that problem solved.” And so it was.

[Bolyai’s Science Absolute of Space is] the most extraordinary two dozen pages in the history of thought!

[Concerning] phosphorescent bodies, and in particular to uranium salts whose phosphorescence has a very brief duration. With the double sulfate of uranium and potassium ... I was able to perform the following experiment: One wraps a Lumière photographic plate with a bromide emulsion in two sheets of very thick black paper, such that the plate does not become clouded upon being exposed to the sun for a day. One places on the sheet of paper, on the outside, a slab of the phosphorescent substance, and one exposes the whole to the sun for several hours. When one then develops the photographic plate, one recognizes that the silhouette of the phosphorescent substance appears in black on the negative. If one places between the phosphorescent substance and the paper a piece of money or a metal screen pierced with a cut-out design, one sees the image of these objects appear on the negative. One can repeat the same experiments placing a thin pane of glass between the phosphorescent substance and the paper, which excludes the possibility of chemical action due to vapors which might emanate from the substance when heated by the sun's rays. One must conclude from these experiments that the phosphorescent substance in question emits rays which pass through the opaque paper and reduces silver salts.
[Although the sun is irrelevant, and he misinterprets the role of phosphorescence, he has discovered the effect of radioactivity.]

[De Morgan relates that some person had made up 800 anagrams on his name, of which he had seen about 650. Commenting on these he says:]
Two of these I have joined in the title-page:
[Ut agendo surgamus arguendo gustamus.]
A few of the others are personal remarks.
Great gun! do us a sum!
is a sneer at my pursuit; but,
Go! great sum! [integral of a to the power u to the power n with respect to u] is more dignified. …
Adsum, nugator, suge!
is addressed to a student who continues talking after the lecture has commenced: …
Graduatus sum! nego
applies to one who declined to subscribe for an M.A. degree.

[Euclid's Elements] has been for nearly twenty-two centuries the encouragement and guide of that scientific thought which is one thing with the progress of man from a worse to a better state. The encouragement; for it contained a body of knowledge that was really known and could be relied on, and that moreover was growing in extent and application. For even at the time this book was written—shortly after the foundation of the Alexandrian Museum—Mathematics was no longer the merely ideal science of the Platonic school, but had started on her career of conquest over the whole world of Phenomena. The guide; for the aim of every scientific student of every subject was to bring his knowledge of that subject into a form as perfect as that which geometry had attained. Far up on the great mountain of Truth, which all the sciences hope to scale, the foremost of that sacred sisterhood was seen, beckoning for the rest to follow her. And hence she was called, in the dialect of the Pythagoreans, ‘the purifier of the reasonable soul.’

[From uranium] there are present at least two distinct types of radiation one that is very readily absorbed, which will be termed for convenience the α radiation, and the other of a more penetrative character, which will be termed the β radiation.

[Helmholtz] is not a philosopher in the exclusive sense, as Kant, Hegel, Mansel are philosophers, but one who prosecutes physics and physiology, and acquires therein not only skill in developing any desideratum, but wisdom to know what are the desiderata, e.g., he was one of the first, and is one of the most active, preachers of the doctrine that since all kinds of energy are convertible, the first aim of science at this time. should be to ascertain in what way particular forms of energy can be converted into each other, and what are the equivalent quantities of the two forms of energy.

[Herschel and Humboldt] stirred up in me a burning zeal to add even the most humble contribution to the noble structure of Natural Science. No one or a dozen other books influenced me nearly so much as these two. I copied out from Humboldt long passages about Teneriffe and read them aloud on one of [my walking excursions].

[I] browsed far outside science in my reading and attended public lectures - Bertrand Russell, H. G. Wells, Huxley, and Shaw being my favorite speakers. (The last, in a meeting at King's College, converted me to vegetarianism - for most of two years!).

[I]magine you want to know the sex of your unborn child. There are several approaches. You could, for example, do what the late film star ... Cary Grant did before he was an actor: In a carnival or fair or consulting room, you suspend a watch or a plumb bob above the abdomen of the expectant mother; if it swings left-right it's a boy, and if it swings forward-back it's a girl. The method works one time in two. Of course he was out of there before the baby was born, so he never heard from customers who complained he got it wrong. ... But if you really want to know, then you go to amniocentesis, or to sonograms; and there your chance of being right is 99 out of 100. ... If you really want to know, you go to science.

[In mathematics] There are two kinds of mistakes. There are fatal mistakes that destroy a theory, but there are also contingent ones, which are useful in testing the stability of a theory.

[J.J.] Sylvester’s methods! He had none. “Three lectures will be delivered on a New Universal Algebra,” he would say; then, “The course must be extended to twelve.” It did last all the rest of that year. The following year the course was to be Substitutions-Théorie, by Netto. We all got the text. He lectured about three times, following the text closely and stopping sharp at the end of the hour. Then he began to think about matrices again. “I must give one lecture a week on those,” he said. He could not confine himself to the hour, nor to the one lecture a week. Two weeks were passed, and Netto was forgotten entirely and never mentioned again. Statements like the following were not unfrequent in his lectures: “I haven’t proved this, but I am as sure as I can be of anything that it must be so. From this it will follow, etc.” At the next lecture it turned out that what he was so sure of was false. Never mind, he kept on forever guessing and trying, and presently a wonderful discovery followed, then another and another. Afterward he would go back and work it all over again, and surprise us with all sorts of side lights. He then made another leap in the dark, more treasures were discovered, and so on forever.

[Relativist] Rel. There is a well-known proposition of Euclid which states that “Any two sides of a triangle are together greater than the third side.” Can either of you tell me whether nowadays there is good reason to believe that this proposition is true?
[Pure Mathematician] Math. For my part, I am quite unable to say whether the proposition is true or not. I can deduce it by trustworthy reasoning from certain other propositions or axioms, which are supposed to be still more elementary. If these axioms are true, the proposition is true; if the axioms are not true, the proposition is not true universally. Whether the axioms are true or not I cannot say, and it is outside my province to consider.

[Science] is not perfect. It can be misused. It is only a tool. But it is by far the best tool we have, self-correcting, ongoing, applicable to everything. It has two rules. First: there are no sacred truths; all assumptions must be critically examined; arguments from authority are worthless. Second: whatever is inconsistent with the facts must be discarded or revised. ... The obvious is sometimes false; the unexpected is sometimes true.

[T]here is little chance that aliens from two societies anywhere in the Galaxy will be culturally close enough to really 'get along.' This is something to ponder as you watch the famous cantina scene in Star Wars. ... Does this make sense, given the overwhelmingly likely situation that galactic civilizations differ in their level of evolutionary development by thousands or millions of years? Would you share drinks with a trilobite, an ourang-outang, or a saber-toothed tiger? Or would you just arrange to have a few specimens stuffed and carted off to the local museum?

[The 1957-1961 years of the U.S. space program] were the sad years in which the joke was that our countdowns ended in "Four, three, two, one, oh shit!"

[The chemical bond] First, it is related to the disposition of two electrons (remember, no one has ever seen an electron!): next, these electrons have their spins pointing in opposite directions (remember, no one can ever measure the spin of a particular electron!): then, the spatial distribution of these electrons is described analytically with some degree of precision (remember, there is no way of distinguishing experimentally the density distribution of one electron from another!): concepts like hybridization, covalent and ionic structures, resonance, all appear, not one of which corresponds to anything that is directly measurable. These concepts make a chemical bond seem so real, so life-like, that I can almost see it. Then I wake with a shock to the realization that a chemical bond does not exist; it is a figment of the imagination that we have invented, and no more real than the square root of - 1. I will not say that the known is explained in terms of the unknown, for that is to misconstrue the sense of intellectual adventure. There is no explanation: there is form: there is structure: there is symmetry: there is growth: and there is therefore change and life.

[The] subjective [historical] element in geologic studies accounts for two characteristic types that can be distinguished among geologists: one considering geology as a creative art, the other regarding geology as an exact science.

[The] weakness of biological balance studies has aptly been illustrated by comparison with the working of a slot machine. A penny brings forth one package of chewing gum; two pennies bring forth two. Interpreted according to the reasoning of balance physiology, the first observation is an indication of the conversion of copper into gum; the second constitutes proof.
[Co-author with David Rittenberg (1906-70).]

[To] explain the phenomena of the mineral kingdom ... systems are usually reduced to two classes, according as they refer to the origin of terrestrial bodies to FIRE or to WATER; and ... their followers have of late been distinguished by the fanciful names of Vulcanists and Neptunists. To the former of these Dr HUTTON belongs much more than to the latter; though, as he employs the agency both of fire and water in his system, he cannot, in strict propriety, be arranged with either.

[Wolfgang Bolyai] was extremely modest. No monument, said he, should stand over his grave, only an apple-tree, in memory of the three apples: the two of Eve and Paris, which made hell out of earth, and that of Newton, which elevated the earth again into the circle of the heavenly bodies.

[Describing the effects of over-indulgence in wine:]
But most too passive, when the blood runs low
Too weakly indolent to strive with pain,
And bravely by resisting conquer fate,
Try Circe's arts; and in the tempting bowl
Of poisoned nectar sweet oblivion swill.
Struck by the powerful charm, the gloom dissolves
In empty air; Elysium opens round,
A pleasing frenzy buoys the lightened soul,
And sanguine hopes dispel your fleeting care;
And what was difficult, and what was dire,
Yields to your prowess and superior stars:
The happiest you of all that e'er were mad,
Or are, or shall be, could this folly last.
But soon your heaven is gone: a heavier gloom
Shuts o'er your head; and, as the thundering stream,
Swollen o'er its banks with sudden mountain rain,
Sinks from its tumult to a silent brook,
So, when the frantic raptures in your breast
Subside, you languish into mortal man;
You sleep, and waking find yourself undone,
For, prodigal of life, in one rash night
You lavished more than might support three days.
A heavy morning comes; your cares return
With tenfold rage. An anxious stomach well
May be endured; so may the throbbing head;
But such a dim delirium, such a dream,
Involves you; such a dastardly despair
Unmans your soul, as maddening Pentheus felt,
When, baited round Citheron's cruel sides,
He saw two suns, and double Thebes ascend.

[Introducing two perfectly ordinary performers of average stature to a circus audience.]
The Punkwat twins! Brentwood is the world's smallest giant, whilst his brother, Elwood, is the largest midget in the world. They baffle science!

[Of the Laputans:] They have likewise discovered two lesser stars, or satellites, which revolve about Mars, whereof the innermost is distant from the centre of the primary planet exactly three of his diameters, and the outermost five; the former revolves in the space of ten hours, and the latter in twenty one and a half.

[On seeing the marsupials in Australia for the first time and comparing them to placental mammals:] An unbeliever … might exclaim “Surely two distinct Creators must have been at work.”

[Students or readers about teachers or authors.] They will listen with both ears to what is said by the men just a step or two ahead of them, who stand nearest to them, and within arm’s reach. A guide ceases to be of any use when he strides so far ahead as to be hidden by the curvature of the earth.

Ac astronomye is an hard thyng,
And yvel for to knowe;
Geometrie and geomesie,
So gynful of speche,
Who so thynketh werche with tho two
Thryveth ful late,
For sorcerie is the sovereyn book
That to tho sciences bilongeth.
Now, astronomy is a difficult discipline, and the devil to learn;
And geometry and geomancy have confusing terminology:
If you wish to work in these two, you will not succeed quickly.
For sorcery is the chief study that these sciences entail.

Compounds formed by chemical attraction, possess new properties different from those of their component parts... chemists have long believed that the contrary took place in their combination. They thought, in fact, that the compounds possessed properties intermediate between those of their component parts; so that two bodies, very coloured, very sapid, or insapid, soluble or insoluble, fusible or infusible, fixed or volatile, assumed in chemical combination, a shade or colour, or taste, solubility or volatility, intermediate between, and in some sort composed of, the same properties which were considered in their principles. This is an illusion or error which modern chemistry is highly interested to overthrow.

Douter de tout ou tout croire, ce sont deux solutions également commodes, qui l’une et l’autre nous dispensent de défléchir.
To doubt everything and to believe everything are two equally convenient solutions; each saves us from thinking.

Ihm in vollem Maaße das Schicksal werde, welches in jeder Erkenntniß, … allezeit der Wahrheit zu Theil ward, der nur ein kurzes Siegesfest beschieden ist, zwischen den beiden langen Zeiträumen, wo sie als parador verdammt und als trivial geringgeschätzt wird.
[It] has always fallen to the lot of truth in every branch of knowledge, … [that] to truth only a brief celebration of victory is allowed between the two long periods during which it is condemned as paradoxical, or disparaged as trivial. The author of truth also usually meets with the former fate.

In a 1852 letter, Nightingale records the opinion of a young surgeon:
The account he gives of nurses beats everything that even I know of. This young prophet says that they are all drunkards, without exception, Sisters and all, and that there are but two whom the surgeon can trust to give the patients their medicines.

La vérité ne diffère de l'erreur qu'en deux points: elle est un peu plus difficile à prouver et beaucoup plus difficile à faire admettre. (Dec 1880)
Truth is different from error in two respects: it is a little harder to prove and more difficult to admit.

Mi è impossibile cingere i fianchi di una ragazza con il mio braccio destro e serrare il suo sorriso nella mia mano sinistra, per poi tentare di studiare i due oggetti separatamente. Allo stesso modo, non ci è possibile separare la vita dalla materia vivente, allo scopo di studiare la sola materia vivente e le sue reazioni. Inevitabilmente, studiando la materia vivente e le sue reazioni, studiamo la vita stessa.
It is impossible to encircle the hips of a girl with my right arm and hold her smile in my left hand, then proceed to study the two items separately. Similarly, we can not separate life from living matter, in order to study only living matter and its reactions. Inevitably, studying living matter and its reactions, we study life itself

Natura non facit saltum or, Nature does not make leaps… If you assume continuity, you can open the well-stocked mathematical toolkit of continuous functions and differential equations, the saws and hammers of engineering and physics for the past two centuries (and the foreseeable future).

Question: If you walk on a dry path between two walls a few feet apart, you hear a musical note or “ring” at each footstep. Whence comes this?
Answer: This is similar to phosphorescent paint. Once any sound gets between two parallel reflectors or walls, it bounds from one to the other and never stops for a long time. Hence it is persistent, and when you walk between the walls you hear the sounds made by those who walked there before you. By following a muffin man down the passage within a short time you can hear most distinctly a musical note, or, as it is more properly termed in the question, a “ring” at every (other) step.

Question: If you were to pour a pound of molten lead and a pound of molten iron, each at the temperature of its melting point, upon two blocks of ice, which would melt the most ice, and why?
Answer: This question relates to diathermancy. Iron is said to be a diathermanous body (from dia, through, and thermo, I heat), meaning that it gets heated through and through, and accordingly contains a large quantity of real heat. Lead is said to be an athermanous body (from a, privative, and thermo, I heat), meaning that it gets heated secretly or in a latent manner. Hence the answer to this question depends on which will get the best of it, the real heat of the iron or the latent heat of the lead. Probably the iron will smite furthest into the ice, as molten iron is white and glowing, while melted lead is dull.

Replying to G. H. Hardy’s suggestion that the number of a taxi (1729) was “dull”: No, it is a very interesting number; it is the smallest number expressible as a sum of two cubes in two different ways, the two ways being 1³ + 12³ and 9³ + 10³.

Socrates: Very good; let us begin then, Protarchus, by asking whether all this which they call the universe is left to the guidance of unreason and chance medley, or, on the contrary, as our fathers have declared, ordered and governed by a marvellous intelligence and wisdom.
Protarchus: Wide asunder are the two assertions, illustrious Socrates, for that which you were just now saying to me appears to be blasphemy, but the other assertion, that mind orders all things, is worthy of the aspect of the world…

Surtout l’astronomie et l’anatomie sont les deux sciences qui nous offrent le plus sensiblement deux grands caractères du Créateur; l’une, son immensité, par les distances, la grandeur, et le nombre des corps célestes; l’autre, son intelligence infinie, par la méchanique des animaux.
Above all, astronomy and anatomy are the two sciences which present to our minds most significantly the two grand characteristics of the Creator; the one, His immensity, by the distances, size, and number of the heavenly bodies; the other, His infinite intelligence, by the mechanism of animate beings.

The Annotated Alice, of course, does tie in with math, because Lewis Carroll was, as you know, a professional mathematician. So it wasn’t really too far afield from recreational math, because the two books are filled with all kinds of mathematical jokes. I was lucky there in that I really didn’t have anything new to say in The Annotated Alice because I just looked over the literature and pulled together everything in the form of footnotes. But it was a lucky idea because that’s been the best seller of all my books.

The Charms of Statistics.—It is difficult to understand why statisticians commonly limit their inquiries to Averages, and do not revel in more comprehensive views. Their souls seem as dull to the charm of variety as that of the native of one of our flat English counties, whose retrospect of Switzerland was that, if its mountains could be thrown into its lakes, two nuisances would be got rid of at once. An Average is but a solitary fact, whereas if a single other fact be added to it, an entire Normal Scheme, which nearly corresponds to the observed one, starts potentially into existence. Some people hate the very name of statistics, but I find them full of beauty and interest. Whenever they are not brutalised, but delicately handled by the higher methods, and are warily interpreted, their power of dealing with complicated phenomena is extraordinary. They are the only tools by which an opening can be cut through the formidable thicket of difficulties that bars the path of those who pursue the Science of man.

Toutes les fois que dans une équation finale on trouve deux quantités inconnues, on a un lieu, l'extrémité de l'une d’elles décrivant une ligne droite ou courbe. La ligne droite est simple et unique dans son genre; les espèces des courbes sont en nombre indéfini, cercle, parabole, hyperbole, ellipse, etc.
Whenever two unknown magnitudes appear in a final equation, we have a locus, the extremity of one of the unknown magnitudes describing a straight line or a curve. The straight line is simple and unique; the classes of curves are indefinitely many,—circle, parabola, hyperbola, ellipse, etc.

Truth then seems to me, in the proper import of the Word, to signifie nothing but the joining or separating of Signs, as the Things signified by them do agree or disagree one with another; which way of joining or separating of Signs, we call Proposition. So that Truth properly belongs only to Propositions: whereof there are two sorts, viz. Mental and Verbal; as there are two sorts of Signs commonly made use of, viz. Ideas and Words.

~~[Misattributed]~~ The shortest path between two truths in the real domain passes through the complex domain.
In fact, this quote is a paraphrase from Paul Painlevé.

1095 … Then after Easter on the eve of St. Ambrose, which is on 4 April [recte 3 April], almost everywhere in this country and almost the whole night, stars in very large numbers were seen to fall from heaven, not by ones or twos, but in such quick succession that they could not be counted.

A book should have either intelligibility or correctness; to combine the two is impossible, but to lack both is to be unworthy of a place as Euclid has occupied in education.

A discovery must be, by definition, at variance with existing knowledge. During my lifetime, I made two. Both were rejected offhand by the popes of the field. Had I predicted these discoveries in my applications, and had those authorities been my judges, it is evident what their decisions would have been.

A discussion between Haldane and a friend began to take a predictable turn. The friend said with a sigh, “It’s no use going on. I know what you will say next, and I know what you will do next.” The distinguished scientist promptly sat down on the floor, turned two back somersaults, and returned to his seat. “There,” he said with a smile. “That’s to prove that you’re not always right.”

A DNA sequence for the genome of bacteriophage ΦX174 of approximately 5,375 nucleotides has been determined using the rapid and simple “plus and minus” method. The sequence identifies many of the features responsible for the production of the proteins of the nine known genes of the organism, including initiation and termination sites for the proteins and RNAs. Two pairs of genes are coded by the same region of DNA using different reading frames.
[Paper co-author]

A game is on, at the other end of this infinite distance, and heads or tails will turn up. What will you wager? According to reason you cannot leave either; according to reason you cannot leave either undone... Yes, but wager you must; there is no option, you have embarked on it. So which will you have. Come. Since you must choose, let us see what concerns you least. You have two things to lose: truth and good, and two things to stake: your reason and your will, your knowledge and your happiness. And your nature has two things to shun: error and misery. Your reason does not suffer by your choosing one more than the other, for you must choose. That is one point cleared. But your happiness? Let us weigh gain and loss in calling heads that God is. Reckon these two chances: if you win, you win all; if you lose, you lose naught. Then do not hesitate, wager that He is.

A great surgeon performs operations for stone by a single method; later he makes a statistical summary of deaths and recoveries, and he concludes from these statistics that the mortality law for this operation is two out of five. Well, I say that this ratio means literally nothing scientifically and gives us no certainty in performing the next operation; for we do not know whether the next case will be among the recoveries or the deaths. What really should be done, instead of gathering facts empirically, is to study them more accurately, each in its special determinism. We must study cases of death with great care and try to discover in them the cause of mortal accidents so as to master the cause and avoid the accidents.

A life is either all spiritual or not spiritual at all. No man can serve two masters.

A living organism must be studied from two distinct aspects. One of these is the causal-analytic aspect which is so fruitfully applicable to ontogeny. The other is the historical descriptive aspect which is unravelling lines of phylogeny with ever-increasing precision. Each of these aspects may make suggestions concerning the possible significance of events seen under the other, but does not explain or translate them into simpler terms.

A man is a poor physician who has not two or three remedies ready for use in every case of illness.

A man of about fifty-four years of age, had begun, five or six months before, to be somewhat emaciated in his whole body...a troublesome vomiting came on, of a fluid which resembl’d water, tinctur’d with soot.... Death took place.... In the stomach...was an ulcerated cancerous tumour.... Betwixt the stomach and the spleen were two glandular bodies, of the bigness of a bean, and in their colour, and substance, not much unlike that tumour which I have describ’d in the stomach.

A man who sets out to justify his existence and his activities has to distinguish two different questions. The first is whether the work which he does is worth doing; and the second is why he does it (whatever its value may be).

A mathematician thinks that two points are enough to define a straight line, while a physicist wants more data.

A metaphysician is one who, when you remark that twice two makes four, demands to know what you mean by twice, what by two, what by makes, and what by four. For asking such questions metaphysicians are supported in oriental luxury in the universities, and respected as educated and intelligent men.

A Native American elder once described his own inner struggles in this manner: Inside of me there are two dogs. One of the dogs is mean and evil. The other dog is good. The mean dog fights the good dog all the time. When asked which dog wins, he reflected for a moment and replied, The one I feed the most.

A reference to the two sorts of doctors is also found in the Republic: “Now you know that when patients do not require medicine, but have only to be put under a regimen, the inferior sort of practitioner is deemed to be good enough; but when medicine has to be given, then the doctor should be more of a man.”

A small cabin stands in the Glacier Peak Wilderness, about a hundred yards off a trail that crosses the Cascade Range. In midsummer, the cabin looked strange in the forest. It was only twelve feet square, but it rose fully two stories and then had a high and steeply peaked roof. From the ridge of the roof, moreover, a ten-foot pole stuck straight up. Tied to the top of the pole was a shovel. To hikers shedding their backpacks at the door of the cabin on a cold summer evening—as the five of us did—it was somewhat unnerving to look up and think of people walking around in snow perhaps thirty-five feet above, hunting for that shovel, then digging their way down to the threshold.

A troubling question for those of us committed to the widest application of intelligence in the study and solution of the problems of men is whether a general understanding of the social sciences will be possible much longer. Many significant areas of these disciplines have already been removed by the advances of the past two decades beyond the reach of anyone who does not know mathematics; and the man of letters is increasingly finding, to his dismay, that the study of mankind proper is passing from his hands to those of technicians and specialists. The aesthetic effect is admittedly bad: we have given up the belletristic “essay on man” for the barbarisms of a technical vocabulary, or at best the forbidding elegance of mathematical syntax.

About ten months ago [1609] a report reached my ears that a certain Fleming [Hans Lippershey] had constructed a spyglass, by means of which visible objects, though very distant from the eye of the observer, were distinctly seen as if nearby... Of this truly remarkable effect several experiences were related, to which some persons gave credence while others denied them. A few days later the report was confirmed to me in a letter from a noble Frenchman at Paris, Jacques Badovere, which caused me to apply myself wholeheartedly to enquire into the means by which I might arrive at the invention of a similar instrument. This I did shortly afterwards, my basis being the theory of refraction. First I prepared a tube of lead, at the ends of which I fitted two glass lenses, both plane on one side while on the other side one was spherically convex and the other concave.

About two million years ago, man appeared. He has become the dominant species on the earth. All other living things, animal and plant, live by his sufferance. He is the custodian of life on earth, and in the solar system. It’s a big responsibility.

About two-thirds of the oxygen in our atmosphere is produced in the surface waters of the sea by phytoplankton, the minute forms of algae that give the sea its slightly green hue, and which initiate the entire food web of the ocean.

Absolute space, that is to say, the mark to which it would be necessary to refer the earth to know whether it really moves, has no objective existence…. The two propositions: “The earth turns round” and “it is more convenient to suppose the earth turns round” have the same meaning; there is nothing more in the one than in the other.

According to our ancient Buddhist texts, a thousand million solar systems make up a galaxy. … A thousand million of such galaxies form a supergalaxy. … A thousand million supergalaxies is collectively known as supergalaxy Number One. Again, a thousand million supergalaxy Number Ones form a Supergalaxy Number Two. A thousand million supergalaxy Number Twos make up a supergalaxy Number Three, and of these, it is stated in the texts that there are a countless number in the universe.

Adam Smith says that nobody ever imagined a god of weight—and he might have added, of the multiplication table either. It may be that the relations of Nature are all as inevitable as that twice two are four.

After a short period spent in Brussels as a guest of a neurological institute, I returned to Turin on the verge of the invasion of Belgium by the German army, Spring 1940, to join my family. The two alternatives left then to us were either to emigrate to the United States, or to pursue some activity that needed neither support nor connection with the outside Aryan world where we lived. My family chose this second alternative. I then decided to build a small research unit at home and installed it in my bedroom.

After the German occupation of Holland in May 1940, the [last] two dark years of the war I spent hiding indoors from the Nazis, eating tulip bulbs to fill the stomach and reading Kramers' book “Quantum Theorie des Elektrons und der Strahlung” by the light of a storm lamp.

After two days in the hospital, I took a turn for the nurse.

Ah, the architecture of this world. Amoebas may not have backbones, brains, automobiles, plastic, television, Valium or any other of the blessings of a technologically advanced civilization; but their architecture is two billion years ahead of its time.

All fossil anthropoids found hitherto have been known only from mandibular or maxillary fragments, so far as crania are concerned, and so the general appearance of the types they represented had been unknown; consequently, a condition of affairs where virtually the whole face and lower jaw, replete with teeth, together with the major portion of the brain pattern, have been preserved, constitutes a specimen of unusual value in fossil anthropoid discovery. Here, as in Homo rhodesiensis, Southern Africa has provided documents of higher primate evolution that are amongst the most complete extant. Apart from this evidential completeness, the specimen is of importance because it exhibits an extinct race of apes intermediate between living anthropoids and man ... Whether our present fossil is to be correlated with the discoveries made in India is not yet apparent; that question can only be solved by a careful comparison of the permanent molar teeth from both localities. It is obvious, meanwhile, that it represents a fossil group distinctly advanced beyond living anthropoids in those two dominantly human characters of facial and dental recession on one hand, and improved quality of the brain on the other. Unlike Pithecanthropus, it does not represent an ape-like man, a caricature of precocious hominid failure, but a creature well advanced beyond modern anthropoids in just those characters, facial and cerebral, which are to be anticipated in an extinct link between man and his simian ancestor. At the same time, it is equally evident that a creature with anthropoid brain capacity and lacking the distinctive, localised temporal expansions which appear to be concomitant with and necessary to articulate man, is no true man. It is therefore logically regarded as a man-like ape. I propose tentatively, then, that a new family of Homo-simidæ be created for the reception of the group of individuals which it represents, and that the first known species of the group be designated Australopithecus africanus, in commemoration, first, of the extreme southern and unexpected horizon of its discovery, and secondly, of the continent in which so many new and important discoveries connected with the early history of man have recently been made, thus vindicating the Darwinian claim that Africa would prove to be the cradle of mankind.

All known living bodies are sharply divided into two special kingdoms, based upon the essential differences which distinguish animals from plants, and in spite of what has been said, I am convinced that these two kingdoms do not really merge into one another at any point.

All minds quote. Old and new make the warp and woof of every moment. There is no thread that is not a twist of these two strands.

All schools, all colleges have two great functions: to confer, and to conceal valuable knowledge.

All that comes above that surface [of the globe] lies within the province of Geography. All that comes below that surface lies inside the realm of Geology. The surface of the earth is that which, so to speak, divides them and at the same time “binds them together in indissoluble union.” We may, perhaps, put the case metaphorically. The relationships of the two are rather like that of man and wife. Geography, like a prudent woman, has followed the sage advice of Shakespeare and taken unto her “an elder than herself;” but she does not trespass on the domain of her consort, nor could she possibly maintain the respect of her children were she to flaunt before the world the assertion that she is “a woman with a past.”

All the different classes of beings which taken together make up the universe are, in the ideas of God who knows distinctly their essential gradations, only so many ordinates of a single curve so closely united that it would be impossible to place others between any two of them, since that would imply disorder and imperfection. Thus men are linked with the animals, these with the plants and these with the fossils which in turn merge with those bodies which our senses and our imagination represent to us as absolutely inanimate. And, since the law of continuity requires that when the essential attributes of one being approximate those of another all the properties of the one must likewise gradually approximate those of the other, it is necessary that all the orders of natural beings form but a single chain, in which the various classes, like so many rings, are so closely linked one to another that it is impossible for the senses or the imagination to determine precisely the point at which one ends and the next begins?all the species which, so to say, lie near the borderlands being equivocal, at endowed with characters which might equally well be assigned to either of the neighboring species. Thus there is nothing monstrous in the existence zoophytes, or plant-animals, as Budaeus calls them; on the contrary, it is wholly in keeping with the order of nature that they should exist. And so great is the force of the principle of continuity, to my thinking, that not only should I not be surprised to hear that such beings had been discovered?creatures which in some of their properties, such as nutrition or reproduction, might pass equally well for animals or for plants, and which thus overturn the current laws based upon the supposition of a perfect and absolute separation of the different orders of coexistent beings which fill the universe;?not only, I say, should I not be surprised to hear that they had been discovered, but, in fact, I am convinced that there must be such creatures, and that natural history will perhaps some day become acquainted with them, when it has further studied that infinity of living things whose small size conceals them for ordinary observation and which are hidden in the bowels of the earth and the depth of the sea.

Among those whom I could never pursuade to rank themselves with idlers, and who speak with indignation of my morning sleeps and nocturnal rambles, one passes the day in catching spiders, that he may count their eyes with a microscope; another exhibits the dust of a marigold separated from the flower with a dexterity worthy of Leuwenhoweck himself. Some turn the wheel of electricity; some suspend rings to a lodestone, and find that what they did yesterday, they can do again to-day.—Some register the changes of the wind, and die fully convinced that the wind is changeable.—There are men yet more profound, who have heard that two colorless liquors may produce a color by union, and that two cold bodies will grow hot of they are mingled: they mingle them, and produce the effect expected, say it is strange, and mingle them again.

An amoeba never is torn apart through indecision, though, for even if two parts of the amoeba are inclined to go in different directions, a choice is always made. We could interpret this as schizophrenia or just confusion, but it could also be a judicious simultaneous sampling of conditions, in order to make a wise choice of future direction.

An expert problem solver must be endowed with two incompatible qualities, a restless imagination and a patient pertinacity.

An inventor is simply a fellow who doesn’t take his education too seriously. You see, from the time a person is six years old until he graduates form college he has to take three or four examinations a year. If he flunks once, he is out. But an inventor is almost always failing. He tries and fails maybe a thousand times. It he succeeds once then he’s in. These two things are diametrically opposite. We often say that the biggest job we have is to teach a newly hired employee how to fail intelligently. We have to train him to experiment over and over and to keep on trying and failing until he learns what will work.

And God made two great lights, great for their use
To man, the greater to have rule by day, The less by night…

And God said, Let there be lights in the firmament of the heavens to separate the day from the night; and let them be for signs and for seasons and for days and years, and let them be lights in the firmament of the heavens to give light upon the earth.” And it was so. And God made the two great lights, the greater light to rule the day, and the lesser light to rule the night; he made the stars also.

And if you want the exact moment in time, it was conceived mentally on 8th March in this year one thousand six hundred and eighteen, but submitted to calculation in an unlucky way, and therefore rejected as false, and finally returning on the 15th of May and adopting a new line of attack, stormed the darkness of my mind. So strong was the support from the combination of my labour of seventeen years on the observations of Brahe and the present study, which conspired together, that at first I believed I was dreaming, and assuming my conclusion among my basic premises. But it is absolutely certain and exact that the proportion between the periodic times of any two planets is precisely the sesquialterate proportion of their mean distances.

And no one has the right to say that no water-babies exist, till they have seen no water-babies existing; which is quite a different thing, mind, from not seeing water-babies; and a thing which nobody ever did, or perhaps will ever do. But surely [if one were caught] ... they would have put it into spirits, or into the Illustrated News, or perhaps cut it into two halves, poor dear little thing, and sent one to Professor Owen, and one to Professor Huxley, to see what they would each say about it.

And of every living thing of all flesh, you shall bring two of every sort into the ark, to keep them alive with you; they shall be male and female. Of the birds according to their kinds, and of the animals according to their kinds, of every creeping thing of the ground according to its kind.

And therefore, sir, as you desire to live,
A day or two before your laxative,
Take just three worms, nor under nor above,
Because the gods unequal numbers love.
These digestives prepare you for your purge,
Of fumetery, centaury, and spurge;
And of ground-ivy add a leaf or two.
All which within our yard or garden grow.
Eat these, and be, my lord, of better cheer:
Your father’s son was never born to fear.

Anglesey has two deserts, one made by Nature, the other made by Man: Newborough and Parys Mountain.

Any experiment may be regarded as forming an individual of a 'population' of experiments which might be performed under the same conditions. A series of experiments is a sample drawn from this population.
Now any series of experiments is only of value in so far as it enables us to form a judgment as to the statistical constants of the population to which the experiments belong. In a great number of cases the question finally turns on the value of a mean, either directly, or as the mean difference between the two qualities.
If the number of experiments be very large, we may have precise information as to the value of the mean, but if our sample be small, we have two sources of uncertainty:— (I) owing to the 'error of random sampling' the mean of our series of experiments deviates more or less widely from the mean of the population, and (2) the sample is not sufficiently large to determine what is the law of distribution of individuals.

Any man who does not make himself proficient in at least two languages other than his own is a fool.

Archimedes, who combined a genius for mathematics with a physical insight, must rank with Newton, who lived nearly two thousand years later, as one of the founders of mathematical physics. … The day (when having discovered his famous principle of hydrostatics he ran through the streets shouting Eureka! Eureka!) ought to be celebrated as the birthday of mathematical physics; the science came of age when Newton sat in his orchard.

Art and Religion are, then, two roads by which men escape from circumstance to ecstasy. Between aesthetic and religious rapture there is a family alliance. Art and Religion are means to similar states of mind.

Art and science work in quite different ways: agreed. But, bad as it may sound, I have to admit that I cannot get along as an artist without the use of one or two sciences. ... In my view, the great and complicated things that go on in the world cannot be adequately recognized by people who do not use every possible aid to understanding.

As a result of the phenomenally rapid change and growth of physics, the men and women who did their great work one or two generations ago may be our distant predecessors in terms of the state of the field, but they are our close neighbors in terms of time and tastes. This may be an unprecedented state of affairs among professionals; one can perhaps be forgiven if one characterizes it epigrammatically with a disastrously mixed metaphor; in the sciences, we are now uniquely privileged to sit side-by-side with the giants on whose shoulders we stand.

As a scientist and geneticist I started to feel that science would probably soon reach the point where its interference into the life processes would be counterproductive if a properly designed governing policy was not implemented. A heavily overcrowded planet, ninety-five percent urbanized with nuclear energy as the main source of energy and with all aspects of life highly computerized, is not too pleasant a place for human life. The life of any individual soon will be predictable from birth to death. Medicine, able to cure almost everything, will make the load of accumulated defects too heavy in the next two or three centuries. The artificial prolongation of life, which looked like a very bright idea when I started research in aging about twenty-five years ago, has now lost its attractiveness for me. This is because I now know that the aging process is so multiform and complex that the real technology and chemistry of its prevention by artificial interference must be too complex and expensive. It would be the privilege of a few, not the method for the majority. I also was deeply concerned about the fact that most research is now either directly or indirectly related to military projects and objectives for power.

As Bertrand Russell once wrote, two plus two is four even in the interior of the sun.

As every circumstance relating to so capital a discovery as this (the greatest, perhaps, that has been made in the whole compass of philosophy, since the time of Sir Isaac Newton) cannot but give pleasure to all my readers, I shall endeavour to gratify them with the communication of a few particulars which I have from the best authority. The Doctor [Benjamin Franklin], after having published his method of verifying his hypothesis concerning the sameness of electricity with the matter lightning, was waiting for the erection of a spire in Philadelphia to carry his views into execution; not imagining that a pointed rod, of a moderate height, could answer the purpose; when it occurred to him, that, by means of a common kite, he could have a readier and better access to the regions of thunder than by any spire whatever. Preparing, therefore, a large silk handkerchief, and two cross sticks, of a proper length, on which to extend it, he took the opportunity of the first approaching thunder storm to take a walk into a field, in which there was a shed convenient for his purpose. But dreading the ridicule which too commonly attends unsuccessful attempts in science, he communicated his intended experiment to no body but his son, who assisted him in raising the kite.
The kite being raised, a considerable time elapsed before there was any appearance of its being electrified. One very promising cloud passed over it without any effect; when, at length, just as he was beginning to despair of his contrivance, he observed some loose threads of the hempen string to stand erect, and to avoid one another, just as if they had been suspended on a common conductor. Struck with this promising appearance, he inmmediately presented his knuckle to the key, and (let the reader judge of the exquisite pleasure he must have felt at that moment) the discovery was complete. He perceived a very evident electric spark. Others succeeded, even before the string was wet, so as to put the matter past all dispute, and when the rain had wetted the string, he collected electric fire very copiously. This happened in June 1752, a month after the electricians in France had verified the same theory, but before he had heard of any thing that they had done.

As I looked down, I saw a large river meandering slowly along for miles, passing from one country to another without stopping. I also saw huge forests, extending along several borders. And I watched the extent of one ocean touch the shores of separate continents. Two words leaped to mind as I looked down on all this: commonality and interdependence. We are one world.

As new areas of the world came into view through exploration, the number of identified species of animals and plants grew astronomically. By 1800 it had reached 70,000. Today more than 1.25 million different species, two-thirds animal and one-third plant, are known, and no biologist supposes that the count is complete.

As one penetrates from seam to seam, from stratum to stratum and discovers, under the quarries of Montmartre or in the schists of the Urals, those animals whose fossilized remains belong to antediluvian civilizations, the mind is startled to catch a vista of the milliards of years and the millions of peoples which the feeble memory of man and an indestructible divine tradition have forgotten and whose ashes heaped on the surface of our globe, form the two feet of earth which furnish us with bread and flowers.

As scientists the two men were contrasting types—Einstein all calculation, Rutherford all experiment ... There was no doubt that as an experimenter Rutherford was a genius, one of the greatest. He worked by intuition and everything he touched turned to gold. He had a sixth sense.
(Reminiscence comparing his friend, Ernest Rutherford, with Albert Einstein, whom he also knew.)

As they discover, from strata to strata and from layer to layer, deep in the quarries of Montmartre or the schists of the Urals, these creatures whose fossilized remains belong to antediluvian civilizations, it will strike terror into your soul to see many millions of years, many thousands of races forgotten by the feeble memory of mankind and by the indestructible divine tradition, and whose piles of ashes on the surface of our globe form the two feet of soil which gives us our bread and our flowers.

As to diseases, make a habit of two things—to help, or at least to do no harm.

Astronomy concerns itself with the whole of the visible universe, of which our earth forms but a relatively insignificant part; while Geology deals with that earth regarded as an individual. Astronomy is the oldest of the sciences, while Geology is one of the newest. But the two sciences have this in common, that to both are granted a magnificence of outlook, and an immensity of grasp denied to all the rest.

At fertilization, these two “haploid” nuclei are added together to make a “diploid” nucleus that now contains 2a, 2b and so on; and, by the splitting of each chromosome and the regulated karyokinetic separation of the daughter chromosomes, this double series is inherited by both of the primary blastomeres. In the resulting resting nuclei the individual chromosomes are apparently destroyed. But we have the strongest of indications that, in the stroma of the resting nucleus, every one of the chromosomes that enters the nucleus survives as a well-defined region; and as the cell prepares for its next division this region again gives rise to the same chromosome (Theory of the Individuality of the Chromosomes). In this way the two sets of chromosomes brought together at fertilization are inherited by all the cells of the new individual. It is only in the germinal cells that the so called reduction division converts the double series into a single one. Out of the diploid state, the haploid is once again generated.

At the beginning of its existence as a science, biology was forced to take cognizance of the seemingly boundless variety of living things, for no exact study of life phenomena was possible until the apparent chaos of the distinct kinds of organisms had been reduced to a rational system. Systematics and morphology, two predominantly descriptive and observational disciplines, took precedence among biological sciences during the eighteenth and nineteenth centuries. More recently physiology has come to the foreground, accompanied by the introduction of quantitative methods and by a shift from the observationalism of the past to a predominance of experimentation.