What is a good definition? For the philosopher or the scientist, it is a definition which applies to all the objects to be defined, and applies only to them; it is that which satisfies the rules of logic. But in… — Henri Poincare Copy Share Image
For a long time the objects that mathematicians dealt with were mostly ill-defined; one believed one knew them, but one represented them with the senses and imagination; but one had but a rough picture and not a precise idea on… — Henri Poincare Copy Share Image
The mathematical facts worthy of being studied are those which, by their analogy with other facts, are capable of leading us to the knowledge… — Henri Poincare Copy Share Image
. . . by natural selection our mind has adapted itself to the conditions of the external world. It has adopted the geometry most… — Henri Poincare Copy Share Image
If we knew exactly the laws of nature and the situation of the universe at the initial moment, we could predict exactly the situation… — Henri Poincare Copy Share Image
Absolute space, that is to say, the mark to which it would be necessary to refer the earth to know whether it really moves,… — Henri Poincare Copy Share Image
Absolute space, that is to say, the mark to which it would be necessary to refer the earth to know whether it really moves,… — Henri Poincare Copy Share Image
A cat is witty, he has nerve, he knows how to do precisely the right thing at the right moment. — Henri Poincare Copy Share Image
In the old days when people invented a new function they had something useful in mind. — Henri Poincare Copy Share Image
Mathematics has a threefold purpose. It must provide an instrument for the study of nature. But this is not all: it has a philosophical… — Henri Poincare Copy Share Image
