“We must never make experiments to confirm our ideas, but simply to control them.”

Now, a living organism is nothing but a wonderful machine endowed with the most marvellous properties and set going by means of the most complex and delicate mechanism.

The eloquence of a scientist is clarity; scientific truth is always more luminous when its beauty is unadorned than when it is tricked out in the embellishments with which our imagination would seek to clothe it.

In science, the best precept is to alter and exchange our ideas as fast as science moves ahead.

We must remain, in a word, in an intellectual disposition which seems paradoxical, but which, in my opinion, represents the true mind of the investigator. We must have a robust faith and yet not believe.

True science teaches us to doubt and, in ignorance, to refrain.

Those who do not know the torment of the unknown cannot have the joy of discovery.

The doubter is a true man of science: he doubts only himself and his interpretations, but he believes in science.

Obervation is a passive science, experimentation is an active science.

The investigator should have a robust faith – and yet not believe.

The fact that knowledge endlessly recedes as the investigator is about to grasp it is what constitutes at the same time his torment and happiness.

If I had to define life in a single phrase, I should clearly express my thought of throwing into relief one characteristic which, in my opinion, sharply differentiates biological science. I should say: life is creation.

First causes are outside the realm of science.

The great experimental principle, then, is doubt, that philosophic doubt which leaves to the mind its freedom and initiative, and from which the virtues most valuable to investigators in physiology and medicine are derived.

A great discovery is a fact whose appearance in science gives rise to shining ideas, whose light dispels many obscurities and shows us new paths.

A discovery is generally an unforeseen relation not included in theory.

Well-observed facts, though brought to light by passing theories, will never die; they are the material on which alone the house of science will at last be built.

Our lives are a battlefield on which is fought a continuous war between the forces that are pledged to confirm our humanity and those determined to dismantle it.

To confer the gift of drawing, we must create an eye that sees, a hand that obeys, a soul that feels; and in this task, the whole life must cooperate. In this sense, life itself is the only preparation for drawing.

But in fact as Secretary of Homeland Security General John Kelly acknowledged at his confirmation hearing, walls and barriers alone are insufficient to insure security.

Books generally just confirm you in what you have, perhaps unwittingly, decided to do already.

We know that the Russian’s interfered in our election and they did it to benefit President Trump. The intelligence agencies confirmed that.

We must never make experiments to confirm our ideas, but simply to control them.

Reality does not conform to the ideal, but confirms it.

There is a logic of colors, and it is with this alone, and not with the logic of the brain, that the painter should conform.