A good method of discovery is to imagine certain members of a system removed and then see how what is left would behave: for example, where would we be if iron were absent from the world: this is an old example.

Absence of evidence is not evidence of absence.

Absence of proof is not proof of absence.

An Englishman, unless asleep, feels an invisible compulsion to be doing something, to consider time as of some importance. With us, according to custom and tradition, the charm of life consists in ease—ease from the absence of compulsion to do anything.

Any country that wants to make full use of all its potential scientists and technologists … must not expect to get the women quite so simply as it gets the men. It seems to me that marriage and motherhood are at least as socially important as military service. Government regulations are framed to ensure (in the United Kingdom) that a man returning to work from military service is not penalized by his absence. Is it utopian, then, to suggest that any country that really wants a woman to return to a scientific career when her children no longer need her physical presence should make special arrangements to encourage her to do so?

But I think that in the repeated and almost entire changes of organic types in the successive formations of the earth—in the absence of mammalia in the older, and their very rare appearance (and then in forms entirely. unknown to us) in the newer secondary groups—in the diffusion of warm-blooded quadrupeds (frequently of unknown genera) through the older tertiary systems—in their great abundance (and frequently of known genera) in the upper portions of the same series—and, lastly, in the recent appearance of man on the surface of the earth (now universally admitted—in one word, from all these facts combined, we have a series of proofs the most emphatic and convincing,—that the existing order of nature is not the last of an uninterrupted succession of mere physical events derived from laws now in daily operation: but on the contrary, that the approach to the present system of things has been gradual, and that there has been a progressive development of organic structure subservient to the purposes of life.

For what is that which we call evil but the absence of good? In the bodies of animals, disease and wounds mean nothing but the absence of health; for when a cure is effected, that does not mean that the evils which were present—namely, the diseases and wounds—go away from the body and dwell elsewhere: they altogether cease to exist; for the wound or disease is not a substance, but a defect in the fleshly substance,—the flesh itself being a substance, and therefore something good, of which those evils—that is, privations of the good which we call health—are accidents. Just in the same way, what are called vices in the soul are nothing but privations of natural good. And when they are cured, they are not transferred elsewhere: when they cease to exist in the healthy soul, they cannot exist anywhere else.

I think it would be a very rash presumption to think that nowhere else in the cosmos has nature repeated the strange experiment which she has performed on earth—that the whole purpose of creation has been staked on this one planet alone. It is probable that dotted through the cosmos there are other suns which provide the energy for life to attendant planets. It is apparent, however, that planets with just the right conditions of temperature, oxygen, water and atmosphere necessary for life are found rarely.
But uncommon as a habitable planet may be, non-terrestrial life exists, has existed and will continue to exist. In the absence of information, we can only surmise that the chance that it surpasses our own is as good as that it falls below our level.

Intelligence is an extremely subtle concept. It’s a kind of understanding that flourishes if it’s combined with a good memory, but exists anyway even in the absence of good memory. It’s the ability to draw consequences from causes, to make correct inferences, to foresee what might be the result, to work out logical problems, to be reasonable, rational, to have the ability to understand the solution from perhaps insufficient information. You know when a person is intelligent, but you can be easily fooled if you are not yourself intelligent.

Man is a credulous animal, and must believe something; in the absence of good grounds for belief, he will be satisfied with bad ones.

Program testing can be a very effective way to show the presence of bugs, but is hopelessly inadequate for showing their absence.

Recently, we’ve reported that we have made all five bases, the compounds that spell out the instructions for all life and are a part of the nucleic acids, RNA and DNA. Not only did we make all five bases but we found them in a meteorite! So that these two things coming together really assure us that the molecules necessary for life can be found in the absence of life. This was the biggest stumbling block.

Scarcely pausing for breath, Vroomfondel shouted, “We don’t demand solid facts! What we demand is a total absence of solid facts. I demand that I may or may not be Vroomfondel!”

Scripture and Nature agree in this, that all things were covered with water; how and when this aspect began, and how long it lasted, Nature says not, Scripture relates. That there was a watery fluid, however, at a time when animals and plants were not yet to be found, and that the fluid covered all things, is proved by the strata of the higher mountains, free from all heterogeneous material. And the form of these strata bears witness to the presence of a fluid, while the substance bears witness to the absence of heterogeneous bodies. But the similarity of matter and form in the strata of mountains which are different and distant from each other, proves that the fluid was universal.

The chief requisite for the making of a good chicken pie is chicken; nay, no amount of culinary legerdemain can make up for the lack of chicken. In the same way, the chief requisite for the history of science is intimate scientific knowledge; no amount of philosophic legerdemain can make up for its absence.

The mass gross absence of sound in space is more than just silence.

The terminology of the layman is an absence of terminology; the precision of the layman is an accuracy of impression rather than an accuracy of specific fact.

The various elements had different places before they were arranged so as to form the universe. At first, they were all without reason and measure. But when the world began to get into order, fire and water and earth and air had only certain faint traces of themselves, and were altogether such as everything might be expected in the absence of God; this, I say, was their nature at that time, and God fashioned them by form and number.

There appears to be a total absence of place names [in southern Sudan]; there are indeed names for regions, areas, but all hamlets (there are scarcely any villages) bear the name of their headman or district head…, which is as ephemeral as the existence of the bearer himself in this unquiet country. Furthermore, residences are shifted every few years, in order to have fresh farmland; added to this the frequent wars, many deaths etc. In contrast, all bodies of water, even the most insignificant ditches, are permanently named. These will be the only guides if future travelers follow my path in this country or wish to trace it.

Unnecessary noise is the most cruel absence of care which can be inflicted either on sick or well.

We have seen that a proton of energy corresponding to 30,000 volts can effect the transformation of lithium into two fast α-particles, which together have an energy equivalent of more than 16 million volts. Considering the individual process, the output of energy in the transmutation is more than 500 times greater than the energy carried by the proton. There is thus a great gain of energy in the single transmutation, but we must not forget that on an average more than 1000 million protons of equal energy must be fired into the lithium before one happens to hit and enter the lithium nucleus. It is clear in this case that on the whole the energy derived from transmutation of the atom is small compared with the energy of the bombarding particles. There thus seems to be little prospect that we can hope to obtain a new source of power by these processes. It has sometimes been suggested, from analogy with ordinary explosives, that the transmutation of one atom might cause the transmutation of a neighbouring nucleus, so that the explosion would spread throughout all the material. If this were true, we should long ago have had a gigantic explosion in our laboratories with no one remaining to tell the tale. The absence of these accidents indicates, as we should expect, that the explosion is confined to the individual nucleus and does not spread to the neighbouring nuclei, which may be regarded as relatively far removed from the centre of the explosion.