Joseph Priestley, in his book upon matter and spirit, quotes from Hallet's discourses, as follows; "I see a man move and hear him speak for some years. From his speech I certainly infer that he thinks, as I do. I then see that man is a being who thinks and acts. After some time the man falls down in my sight, grows cold and stiff, and speaks and acts no more. Is it not then natural to conclude that he thinks no more; as the only reason I had to believe that he did think was his motion and his speech. And now that his motion and speech have ceased, I have lost the only way of proving that he had the power of thought. Upon this sudden death, one visible thing, the one man, has greatly changed. Whence could I infer that the same being consisted of two parts, and that the inward part continues to live and think, and flies away from the body? When the outward part ceases to live and move, it looks as if the whole _man_ was gone, and that he, with all his powers, ceases at the same time. His motion and thought both die together, as far as I can discern. The powers of thought, of speech and motion, equally depend upon the body, and run the same fate in case of declining age. When a man dies through old age, I perceive his powers of speech, motion, and thought decay and die together, and by the same degrees. That moment he ceases to move and breathe he appears to cease to think, too. When I am left to my reason it seems to me that my power of thought depends as much upon the body as my sight and hearing. I could not think in infancy; my power of thought, of sight, and of feeling are equally liable to be obstructed by the body. A blow on the head has deprived a man of thought, who could yet see, and feel and move; so naturally the power of thinking seems as much to belong to the body as any power of man whatsoever. Naturally there appears no more reason to suppose that a man can think out of the body than he can hear sounds and feel cold out of the body."