(source) 
Augustus De Morgan
(27 Jun 1806  18 Mar 1871)

Science Quotes by Augustus De Morgan (25 quotes)
>> Click for Augustus De Morgan Quotes on  Mathematics 
>> Click for Augustus De Morgan Quotes on  Mathematics 
[About Francis Baily] The history of the astronomy of the nineteenth century will be incomplete without a catalogue of his labours. He was one of the founders of the Astronomical Society, and his attention to its affairs was as accurate and minute as if it had been a firm of which he was the chief clerk, with expectation of being taken into partnership.
— Augustus De Morgan
As to writing another book on geometry [to replace Euclid] the middle ages would have as soon thought of composing another New Testament.
— Augustus De Morgan
Common integration is only the memory of differentiation...
— Augustus De Morgan
Considerable obstacles generally present themselves to the beginner, in studying the elements of Solid Geometry, from the practice which has hitherto uniformly prevailed in this country, of never submitting to the eye of the student, the figures on whose properties he is reasoning, but of drawing perspective representations of them upon a plane. ...I hope that I shall never be obliged to have recourse to a perspective drawing of any figure whose parts are not in the same plane.
— Augustus De Morgan
During the last two centuries and a half, physical knowledge has been gradually made to rest upon a basis which it had not before. It has become mathematical. The question now is, not whether this or that hypothesis is better or worse to the pure thought, but whether it accords with observed phenomena in those consequences which can be shown necessarily to follow from it, if it be true
— Augustus De Morgan
Every science that has thriven has thriven upon its own symbols: logic, the only science which is admitted to have made no improvements in century after century, is the only one which has grown no symbols.
— Augustus De Morgan
Great fleas have little fleas upon their backs to bite 'em,
And little fleas have lesser fleas, and so ad infinitum.
And the great fleas themselves, in turn have, greater fleas to go on;
While these again have greater still, and greater still, and so on.
[He was imitating: 'So, naturalists observe, a flea Has smaller fleas that on him prey; And these have smaller still to bite 'em; And so proceed ad infinitum.' Poetry, a Rhapsody, by Jonathan Swift.]
And little fleas have lesser fleas, and so ad infinitum.
And the great fleas themselves, in turn have, greater fleas to go on;
While these again have greater still, and greater still, and so on.
[He was imitating: 'So, naturalists observe, a flea Has smaller fleas that on him prey; And these have smaller still to bite 'em; And so proceed ad infinitum.' Poetry, a Rhapsody, by Jonathan Swift.]
— Augustus De Morgan
I don't quite hear what you say, but I beg to differ entirely with you.
— Augustus De Morgan
I end with a word on the new symbols which I have employed. Most writers on logic strongly object to all symbols. ... I should advise the reader not to make up his mind on this point until he has well weighed two facts which nobody disputes, both separately and in connexion. First, logic is the only science which has made no progress since the revival of letters; secondly, logic is the only science which has produced no growth of symbols.
— Augustus De Morgan
I was x years old in the year x^{2}.
When asked about his age (43).
When asked about his age (43).
— Augustus De Morgan
Imagine a person with a gift of ridicule [He might say] First that a negative quantity has no logarithm; secondly that a negative quantity has no square root; thirdly that the first nonexistent is to the second as the circumference of a circle is to the diameter.
— Augustus De Morgan
Isaac Newton was born at Woolsthorpe, near Grantham, in Lincolnshire, on Christmas Day, 1642: a weakly and diminutive infant, of whom it is related that, at his birth, he might have found room in a quart mug. He died on March the 20th, 1727, after more than eightyfour years of more than average bodily health and vigour; it is a proper pendant to the story of the quart mug to state that he never lost more than one of his second teeth.
— Augustus De Morgan
It is easier to square the circle than to get round a mathematician.
— Augustus De Morgan
It was long before I got at the maxim, that in reading an old mathematician you will not read his riddle unless you plough with his heifer; you must see with his light, if you want to know how much he saw.
— Augustus De Morgan
Lagrange, in one of the later years of his life, imagined that he had overcome the difficulty (of the parallel axiom). He went so far as to write a paper, which he took with him to the Institute, and began to read it. But in the first paragraph something struck him that he had not observed: he muttered: 'Il faut que j'y songe encore', and put the paper in his pocket.' [I must think about it again]
— Augustus De Morgan
Metaphysics. The science to which ignorance goes to learn its knowledge, and knowledge to learn its ignorance. On which all men agree that it is the key, but no two upon how it is to be put into the lock.
— Augustus De Morgan
Modern discoveries have not been made by large collections of facts, with subsequent discussion, separation, and resulting deduction of a truth thus rendered perceptible. A few facts have suggested an hypothesis, which means a supposition, proper to explain them. The necessary results of this supposition are worked out, and then, and not till then, other facts are examined to see if their ulterior results are found in Nature.
— Augustus De Morgan
One day at least in every week,
The sects of every kind
Their doctrines here are sure to seek,
And just as sure to find.
The sects of every kind
Their doctrines here are sure to seek,
And just as sure to find.
— Augustus De Morgan
The Astronomers Drinking Song
Astronomers! What can avail
Those who calumniate us;
Experiment can never fail
With such an apparatus
Astronomers! What can avail
Those who calumniate us;
Experiment can never fail
With such an apparatus
— Augustus De Morgan
The gambling reasoner is incorrigible; if he would but take to the squaring of the circle, what a load of misery would be saved.
— Augustus De Morgan
The genius of Laplace was a perfect sledge hammer in bursting purely mathematical obstacles; but, like that useful instrument, it gave neither finish nor beauty to the results. In truth, in truism if the reader please, Laplace was neither Lagrange nor Euler, as every student is made to feel. The second is power and symmetry, the third power and simplicity; the first is power without either symmetry or simplicity. But, nevertheless, Laplace never attempted investigation of a subject without leaving upon it the marks of difficulties conquered: sometimes clumsily, sometimes indirectly, always without minuteness of design or arrangement of detail; but still, his end is obtained and the difficulty is conquered.
— Augustus De Morgan
The imaginary expression √(a) and the negative expression b, have this resemblance, that either of them occurring as the solution of a problem indicates some inconsistency or absurdity. As far as real meaning is concerned, both are imaginary, since 0  a is as inconceivable as √(a).
— Augustus De Morgan
The moving power of mathematical invention is not reasoning but imagination.
— Augustus De Morgan
This mysterious 3.141592..., which comes in at every door and window, and down every chimney.
— Augustus De Morgan
We know that mathematicians care no more for logic than logicians for mathematics. The two eyes of science are mathematics and logic; the mathematical set puts out the logical eye, the logical set puts out the mathematical eye; each believing that it sees better with one eye than with two.
Note that De Morgan, himself, only had sight with only one eye.
Note that De Morgan, himself, only had sight with only one eye.
— Augustus De Morgan
Quotes by others about Augustus De Morgan (1)
De Morgan was explaining to an actuary what was the chance that a certain proportion of some group of people would at the end of a given time be alive; and quoted the actuarial formula, involving p [pi], which, in answer to a question, he explained stood for the ratio of the circumference of a circle to its diameter. His acquaintance, who had so far listened to the explanation with interest, interrupted him and exclaimed, 'My dear friend, that must be a delusion, what can a circle have to do with the number of people alive at a given time?'
See also:
 27 Jun  short biography, births, deaths and events on date of De Morgan's birth.
 Memoir of Augustus De Morgan, by Sophia Elizabeth (Frend) De Morgan.  book suggestion.
 Booklist for Augustus De Morgan.