sense, these would yet bear to us as complete significance of the various contrasting vicissitudes of life, as do our muscular activities to the common observer. As there are distinctive earmarks common to all healthy organs, and others common to all unhealthy organs, whatever their particular functions, or whatever the animal, so there are ear-marks common to those neural activities whose function is to continue certain beneficial processes, and contrasting ear-marks for other neural activities whose function is discontinuance. And these traits hold good for all kinds of sense, and for most creatures. To follow these out and to note them would throw much light on the common mistake of identifying all desires with pleasure, and all aversions with pains. But we content ourselves here with making plain that, from the first, the desires of our worm would be of different make-up from its aversions, and that, in so far as these contrasting states were representative of like contrasts in outer events, to that degree they would constitute for the worm a knowledge of these outer differences, and would constitute its love or hate of them.
But, if the nervous organism of our creature should now be changed so that most of these occurrences which I have defined as desires should be transacted in terms of one specific sense, and those of aversion in terms of a different sense, we see at once that new and important characteristics would thus be introduced mentally distinguishing desire from aversion. In this case, we should bear in mind, however, that the essential features by which we should still test desires and hates would not lie in the facts that most desires were of one particular kind of sense, and aversions of another kind, but, as described above, in certain peculiar relations based on the corresponding physical functions which such mental states bore to other mental states.
Our worm had one sense; we have several. In light of what we know of specialization, we should now inquire whether something like what we discussed in our last paragraph did not really take place in the development of the worm to man.
We have already discovered that it is the particular function
