You see, then, to what we reduce all the jargon of the metaphysicians, all the profound reveries which for so many ages have been so industriously hawked about in defence of the soul of man; an immaterial substance, of which no living being can form an idea; a spirit, that is to say, a being totally different from any thing we know. All the theological verbiage ends here, by telling us, in a round of pompous terms,--fooleries that impose on the ignorant,--that we do not know what essence the soul is of; but we call it a spirit because of its nature, and because we feel ourselves agitated by some unknown agent; we cannot comprehend the mechanism of the soul; yet can we feel ourselves moved, as it were, by an effect of the power of God, whose essence is far removed from ours, and more concealed from us than the human soul itself. By the aid of this language, from which you cannot possibly learn any thing, you will be as wise, Madam, as all the theologians in the world.
If you would desire to form ideas the most precise of yourself, banish from you the prejudices of a vain theology, which only consists in repeating words without attaching any new ideas to them, and which are insufficient to distinguish the soul from the body, which appear only capable of multiplying beings without reason, of rendering more incomprehensible and more obscure, notions less distinct than we already have of ourselves. These notions should be at least the most simple and the most exact, if we consult our nature, experience, and reason. They prove that man knows nothing but by his material sensible organs, that he sees only by his eyes, that he feels by his touch, that he hears by his ears; and that when either of these organs is actually deranged, or has been previously wanting, or imperfect, man can have none of the ideas that organ is capable of furnishing him with,--neither thoughts, memory, reflection, judgment, desire, nor will. Experience shows us that corporeal and material beings are alone capable of being moved and acted upon, and that without those organs we have enumerated the soul thinks not, feels not, wills not, nor is moved. Every thing shows us that the soul undergoes always the same vicissitudes as the body; it grows to maturity, gains strength, becomes weak, and puts on old age, like the body; in fine, every thing we can understand of it goes to prove that it perishes with the body. It is indeed folly to pretend that man will feel when he has no organs appropriate for that sentiment; that he will see and hear without eyes or ears; that he will have ideas without having senses to receive impressions from physical objects, or to give rise to perceptions in his understanding; in fine, that he will enjoy or suffer when he has no longer either nerves or sensibility.