The dogma of the immortality of the soul supposes the soul to be a simple substance; in a word, a spirit. But I ask again, what is a spirit? "It is," say you, "a substance void of extension, incorruptible, having nothing common with matter." If so, how is your soul born, and how does it grow, how does it strengthen or weaken itself, how does it get disordered and grow old, in the same progression as your body?

To all these questions you answer, that these are mysteries. If so, you cannot understand them. If you cannot understand them, why do you decide about a thing, of which you are unable to form the least idea? To believe or affirm any thing, it is necessary, at least, to know in what it consists. To believe in the existence of your immaterial soul, is to say, that you are persuaded of the existence of a thing, of which it is impossible for you to form any true notion; it is to believe in words without meaning. To affirm that the thing is as you say, is the height of folly or vanity.