Parkhurst: (A distinguished Hebrew lexicographer.) As a noun, nephesh hath been supposed to signify the spiritual part of man, or what we commonly call the soul. I must, for myself, confess that I can find no passage where it hath undoubtedly this meaning.
Hobbes: Spirit is synonymous with ghost—a mere phantom of the imagination.
Locke: (“Understanding,” p. 419.) We can no more know that there are finite spirits really existing, by the idea we have of such things in our minds, than by the ideas any one has of fairies, or centaurs; he can come to know that things answering those ideas do really exist.
Voltaire: The Greeks distinguish three sorts of souls—Psyche, signifying the sensitive soul—the soul of the senses; hence it was that Love, the son of Aphrodite, had so much passion for Psyche, and that she loved him so tenderly. Pneuma, the breath which gave life and motion to the whole machine, and which we have rendered by spiritus—spirit—a vague term which has received a thousand different acceptations. And lastly, Nous, intelligence. Thus we possess three souls, without having the slightest notion of any of them.... What are we to think of a child with two heads, which is otherwise well formed? Some say that it has two souls, because it is furnished with two pineal glands, with two callous substances, with two sensoria communia. Others answer, that there cannot be two souls with but one breast and one navel.... The word soul is one of those which everyone pronounces without understanding it. We understand those things of which we have an idea, but we have no idea of soul—spirit; therefore, we do not understand it.
John Calvin: The soul is an immortal essence, the nobler part of man. It is a creation out of nothing, not an emanation; it is essence without motion, not motion without essence. It is not properly bounded by space, still it occupies the body as a habitation, animating its parts and endowing its organs for their several functions.
Dugald Stewart: Although we have the strongest evidence that there is a thinking and sentient principle within us, essentially distinct from matter, yet we have no direct evidence of the possibility of this principle exercising its various powers in a separate state from the body. On the contrary, the union of the two, while it subsists, is evidently of the most intimate nature.
Joseph Priestly: It being a rigid canon of the Newtonian logic not to multiply causes without necessity, we should adhere to a single substance until it be shown, which cannot be, that the properties of mind are incompatible with the properties of matter. He was opposed to protecting and perpetuating absurdity by dodging behind mystery. That there is no difference between spiritual substance and nothing at all. That the doctrine of a separate soul embarrasses the whole system of Christianity.
McBeth: The times have been that when the brains were out the man would die, and there an end.
Buchner: Experience and daily occupation teach us that the spirit perishes with the material substratum—that man dies. (“Matter and Force.”)
Burmeister: That the soul of a deceased person does not re-appear after death, is not contested by rational people. Spirits and ghosts are only seen by diseased or superstitious individuals.