The Foundations of Science: Science and Hypothesis, the Value of Science, Science and Method

“To doubt everything and to believe everything are two equally convenient solutions; each saves us from thinking.””

— Henri Poincaré

“The geometric language is after all only a language. Space is only a word that we have believed a thing.””

— Henri Poincaré

“The readings we shall be able to make on our instruments at any instant will depend only on the readings we could have made on these same instruments at the initial instant.””

— Henri Poincaré

“Correlative movement' therefore constitutes the sole connection between two phenomena which otherwise we never should have dreamt of likening.””

— Henri Poincaré

“In general, the totality A will have nothing in common with the totality A´, nor the totality B with the totality B´. The transition from the totality A to the totality B and that from the totality A´ to the totality B´ are therefore two changes which in themselves have in general nothing in common. And yet we regard these two changes both as displacements and, furthermore, we consider them as the same displacement. How can that be? It is simply because they can both be corrected by the same correlative movement of our body.””

— Henri Poincaré

“When a body changes its place and its shape, we can no longer, by appropriate movements, bring back our sense-organs into the same relative situation with regard to this body; consequently we can no longer reestablish the primitive totality of impressions.””

— Henri Poincaré

“It follows from this that sight and touch could not have given us the notion of space without the aid of the 'muscular sense.””

— Henri Poincaré

“None of our sensations, isolated, could have conducted us to the idea of space; we are led to it only in studying the laws, according to which these sensations succeed each other.””

— Henri Poincaré

“What I do see is that the sensations which correspond to movements in the same direction are connected in my mind by a mere association of ideas. It is to this association that what we call 'the sense of direction' is reducible. This feeling therefore can not be found in a single sensation””

— Henri Poincaré