7. We come to the same result by examining the sense of pain. We say there is pain in the finger: the trouble is doubtless in the finger, but our opponents must admit that the sensation of the pain is in the centre of consciousness. The suffering member is one thing, the sense of suffering is another: how does this happen?
By transmission, they will say: the psychic pneuma [= the semi-material principle of life] stationed at the finger suffers first; and stage by stage the trouble is passed on until at last it reaches the centre of consciousness.
But on this theory, there must be a sensation in the spot first suffering pain, and another sensation at a second point of the line of transmission, another in the third and so on; many sensations, in fact an unlimited series, to deal with one pain; and at the last moment the centre of consciousness has the sensation of all these sensations and of its own sensation to boot. Or to be exact, these serial sensations will not be of the pain in the finger: the sensation next in succession to the suffering finger will be of pain at the joint, a third will tell of a pain still higher up: there will be a series of separate pains: The centre of consciousness will not feel the pain seated at the finger, but only that impinging upon itself: it will know this alone, ignore the rest and so have no notion that the finger is in pain.
Thus: Transmission would not give sensation of the actual condition at the affected spot: it is not in the nature of body that where one part suffers there should be knowledge in another part; for body is a magnitude, and the parts of every magnitude are distinct parts; therefore we need, as the sentient, something of a nature to be identical to itself at any and every spot; this property can belong only to some other form of being than body.