Psychophysical Parallelism 1 1 



This principle, now made the assumption of experimental 

 work in psychophysics, would seem to involve, and also 

 to be supported by, certain other formulas which are a 

 part of general scientific procedure. 



First, the principle of equal continuity, to the effect that 

 there can be no breaks in either series of changes, the 

 brain changes or the conscious changes, without a corre- 

 sponding break in the other ; in other words, if one of the 

 series be continuous, the other must be continuous also. 

 This is referred to again below. 



Second, the principle of uniformity, to the effect that 

 the sort of modifications which are associated one with 

 another in brain and mind are always the same ; that 

 is, if a certain brain process be correctly hit upon as 

 essentially associated with a certain conscious state, then 

 the concomitance of these two terms may be looked for 



The word ' parallelism ' has been in use for a long time in philosophy and 

 psychology for the relation of body and mind, and it is impossible to discard 

 it in the present connection. Yet the biologists have used it also for the rela- 

 tion expressed much better by the term ' recapitulation' (so Cope), and also 

 for the ' parallel ' or concurrent direction of development and evolution as 

 determined by any given influences. In order to avoid such confusion, I shall 

 use ' parallelism ' for the psychophysical relation as explained immediately 

 above, ' concurrence ' for the determination of development and evolution in 

 a common direction, and ' recapitulation ' for the relation of the two series 

 whereby development reproduces evolution. The term ' concurrence ' in such 

 a sense is suggested in my Dictionary of Philosophy and Psychology, art. 

 ' Organic Selection.' For further illustration, we may say that psychophysical 

 parallelism is both ' individual ' and ' racial,' and is found to illustrate both 

 recapitulation (from the fact that the mental and organic series in develop- 

 ment recapitulate respectively those of evolution that is, if either series does, 

 the other, by the law of parallelism, must also), and also 'concurrence' (as 

 a fact, i.e., based on researches which show that evolution follows a course 

 first marked out by individual development). Recurring to an earlier sugges- 

 tion (p. 3, above) we may note that all three of these conceptions are ' inter- 

 genetic,' or ' ontophyletic ' (the former term being the one which I prefer, 

 and shall use). 



