Henri Poincaré

The only reality is the one we construct.

The human mind is not a passive mirror reflecting the world, but an active creator of it.

The principle of causality is not an absolute truth, but a convenient postulate.

The notion of infinity is a product of the human mind, not a property of the world.

The most beautiful theories are those that are the most simple.

The scientist must be a skeptic, but not a cynic.

The true reality is not what we see, but what we imagine.

The laws of physics are not discovered, but invented.

The most profound truths are often the most simple.

The scientist must be a dreamer, but also a realist.

The most important discoveries are those that challenge our preconceived notions.

The laws of logic are not laws of thought, but laws of language.

The true nature of reality is not accessible to us directly, but only through our theories.

It is through science that we prove, but through intuition that we discover.

Thought is only a flash between two long nights, but this flash is everything.

If nature were not beautiful, it would not be worth knowing, and if nature were not worth knowing, life would not be worth living.

The mind uses its faculty for creativity only when experience forces it to do so.

One would have to have completely forgotten the history of science so as not to remember that the desire to know nature has had the most constant and the happiest influence on the development of mathematics.

A collection of facts is no more a science than a heap of stones is a house.

Mathematics is the art of giving the same name to different things. [...] The thing that matters is the analogy, the resemblance of form.