"[T]here may be a farther difference in the constitution of the nerves belonging to the different senses, or there may be so many circumstances that affect or modify their vibrations, that they may be as distinguishable from one another, as different human voices sounding the same note; and probably no two individuals of the human race can sound the same note so much alike, as that they could not be distinguished from one another."
— Priestley, Joseph (1733-1804)
See Hartley’s Theory of the Human Mind, on the Principle of the Association of Ideas; With Essays Relating to the Subject of It. By Joseph Priestley, LL. D. F. R. S. (London: Printed for J. Johnson, No. 72, St. Paul’s Church-Yard, 1775). <Link to ESTC>