“Mind modifies body involuntarily.”

Vol. 2, bk. 8, ch. 7
Enquiry Concerning Political Justice (1793)
Context: Let us here return to the sublime conjecture of Franklin, that “mind will one day become omnipotent over matter.” If over all other matter, why not over the matter of our own bodies? If over matter at ever so great a distance, why not over matter which, however ignorant we may be of the tie that connects it with the thinking principle, we always carry about with us, and which is in all cases the medium of communication between that principle and the external universe? In a word, why may not man be one day immortal?
The different cases in which thought modifies the external universe are obvious to all. It is modified by our voluntary thoughts or design. We desire to stretch out our hand, and it is stretched out. We perform a thousand operations of the same species every day, and their familiarity annihilates the wonder. They are not in themselves less wonderful than any of those modifications which we are least accustomed to conceive. — Mind modifies body involuntarily.