The soul is... but an empty word, of which no one has any idea, and which an enlightened man should use only to signify the part in us that thinks...

Man has been trained in the same way as animals. He has become an author, as they became beasts of burden.

What was man before the invention of words and the knowledge of language? An animal..

Let us not limit the resources of nature; they are infinite, especially when reinforced by great art.

Among animals, some learn to speak and sing; they remember tunes, and strike the notes as exactly as a musician. Others, for instance the ape, show more intelligence... would it be absolutely impossible to teach the ape a language? I do not think so.

A mere nothing, a tiny fibre, something that could never be found by the most delicate anatomy, would have made of Erasmus and Fontenelle two idiots, and Fontenelle himself speaks of this very fact in one of his best dialogues.

In general, the form and the structure of the brains of quadrupeds are almost the same as those of the brain of man...

The, diverse states of the soul are always correlative with those of the body.

A brilliant man is his own best company, unless he can find other company of the same sort.

A geometrician has learned to perform the most difficult demonstrations and calculations, as a monkey has learned to take his little hat off and on...

As a violin string or a harpsichord key vibrates and gives forth sound, so the cerebral fibres, struck by waves of sound, are stimulated to render or repeat the words that strike them.

He who has the most imagination should be regarded as having the most intelligence or genius, for all these words are synonymous...

If one's organism is... the preeminent advantage, and the source of all others, education is the second. The best made brain would be a total loss without it...

Whatever the virtue may be, from whatever source it may come, it is worthy of esteem... Mind, beauty, wealth, nobility, although the children of chance, all have their own value, as skill, learning and virtue have theirs.

Man's preeminent advantage is his organism. ...Only through nature do we have any good qualities; to her we owe all that we are.

Imagination is the soul, since it plays all the roles of the soul.

Why should we divide the sensitive principle which thinks in man? ...For a thing that is divided can no longer without absurdity be regarded as indivisible.

Everything is the work of imagination, and... all the faculties of the soul can be correctly reduced to pure imagination...

The sciences that are expressed by numbers or by other small signs, are easily learned; and... this facility rather than its demonstrability is what has made the fortune of algebra.

The mind, like the body, has its contagious diseases and its scurvy. …We catch everything from those with whom we come in contact; their gestures, their accent, etc.

The soul follows the progress of the body, as it does the progress of education.

One needs only eyes to see the necessary influence of old age on reason.

There comes up another difficulty which more nearly concerns our vanity: namely, the impossibility of our conceiving this property [the faculty of feeling] as a dependence or attribute of matter.

We have now but to prove a third attribute: I mean the faculty of feeling which the philosophers of all centuries have found in this same substance. ...The Cartesians have made, in vain, to rob matter of this faculty. But in order to avoid insurmountable difficulties, they have flung themselves into a labyrinth from which they have thought to escape by this absurd system "that animals are pure machines."An opinion so absurd has never gained admittance among philosophers... Experience gives us no less proof of the faculty of feeling in animals than of feeling in men.

The Christian Scholastics... might have shown that God Himself said that He had "imprinted an active principle in the elements of matter (Gen. i; Is. lxvi).

Descartes, a genius made to blaze new paths and to go astray in them, supposed with some other philosophers that God is the only efficient cause of motion, and that every instant He communicates motion to all bodies. But this opinion is but an hypothesis which he tried to adjust to the light of faith; and in so doing he was no longer attempting to speak as a philosopher or to philosophers. Above all he was not addressing those who can be convinced only by the force of evidence.

If we demonstrate this moving principle, if we show that matter, far from being as indifferent as it is supposed to be, to movement and to rest, ought to be regarded as an active, as well as a passive substance, what resource can be left to those who have made its essence consist in extension?

The ancients, persuaded that there is no body without a moving force, regarded the substance of bodies as composed of two primitive attributes. It was held that, through one of these attributes, this substance has the capacity for moving and, through the other, the capacity for being moved.

Before Descartes, some of the ancients made the essence of matter consist in solid extension. But this opinion, of which all the Cartesians have made much, has at all times been victoriously combated...

Write as if thou wert alone in the universe and hadst nothing to fear from the jealousies and prejudices of the people. Otherwise thou wilt miss thy purpose.

We know in bodies only matter, and we observe the faculty of feeling only in bodies: on what foundation then can we erect an ideal being, disowned by all our knowledge?

We must admit, with the same frankness, that we are ignorant whether matter has in itself the faculty of feeling, or only the power of acquiring it by those modifications or forms to which matter is susceptible; for it is true that this faculty of feeling appears only in organic bodies.This is then another new faculty which might exist only potentially in matter, like all the others which have been mentioned; and this was the hypothesis of the ancients, whose philosophy, full of insight and penetration, deserves to be raised above the ruins of the philosophy of the moderns.

The human body is a machine which winds its own springs.

Let us... take in our hands the staff of experience... To be blind and to think that one can do without this staff is the worst kind of blindness.

Either everything is illusion, nature as well as revelation, or experience alone can explain faith.

Man... whatever the origin of his soul, if it is pure, noble, and lofty, it is a beautiful soul which dignifies the man endowed with it.

If there is a revelation, it can not then contradict nature.

I reduce to two the systems of philosophy which deal with man's soul. The first and older system is materialism; the second is spiritualism.

It is not enough for a wise man to study nature and truth; he should dare state truth for the benefit of the few who are willing and able to think.

Ancient philosophy will always hold its own among those who are worthy to judge it, because it forms... a system that is solid and well articulated like the body, whereas all these scattered members of modern philosophy form no system.

A good prescription is still more profitable than an absolution.