ESSAYS 307 



of hypotheses framed and tested in the manner described ; it is therefore a 

 knowledge concerned solely with processes of change. Can we, then, be said 

 to know the nature of things ? The answer is, that we know this in the 

 same sense as we know the processes ; for we are unable to form ideas of 

 change sufficiently definite to serve as a basis of forecast, without presup- 

 posing some thing which undergoes the change, and we are thus constrained 

 to include this as an accessory to our hypothesis of the process of change. 

 To every such thing we attribute properties adapting it to the conditions of 

 the hypothesis, and these attributed properties constitute what we know of 

 its nature. Thus our knowledge of things is bound up with the same hypo- 

 theses as our knowledge of processes ; the one is essential to the other, and 

 both are equally certain, or equally uncertain. A logical priority attaches 

 to things because their existence is supposed as a condition precedent to 

 their changes ; but it should be remembered, that in relation to knowledge 

 the order is reversed, since it is experience of changes which gives rise to 

 ideas of something undergoing change. 



Now, knowing is in itself a process, and here, as in other cases, if definite 

 forecasts are to be made, a basis must be provided for calculation by sup- 

 posing something which undergoes the changes in that process. Tradition- 

 ally this has been regarded as something entirely distinct from matter ; 

 it was called the " Mind," and was credited with any properties or 

 " faculties " which would serve for the classification of such changes as 

 were considered to be purely mental. 



This hypothesis has, however, two great disadvantages ; in the first 

 place, although the mind cannot be supposed to be entirely independent of 

 the functions performed by the body in sensation, yet no satisfactory theory 

 was ever found for the connection between the material body and the non- 

 material Mind ; and secondly, since the processes of a non-material entity 

 could not be paralleled with any previously known process, the hypotheses 

 concerning them could not be subjected to verification by the method 

 applicable to other systematised knowledge. These difficulties vanish if 

 we regard both sensation and the other changes involved in the process of 

 knowing as being equally functions of the nervous system ; a view which 

 seems to accord with all that I have been able to learn of modern advances 

 in nervous physiology. 



Taking, then, the nervous system as the thing which undergoes the phy- 

 sical changes whose subjective, or mental, aspect is knowing, the following 

 theory may be framed. 



The general function of the system is to respond to stimulus by a dis- 

 turbance of equilibrium and a liberation of energy which affects the whole 

 organism in some degree, but discharges itself mainly along definite lines 

 of least resistance. For the most part these lines follow the paths of pre- 

 vious discharges, since each discharge records its passage by leaving its 

 nerve-track in a condition of reduced resistance. The reduction is a maxi- 

 mum during the actual passage of the discharge ; afterwards there is some 

 return toward the original resistance, though this is not always completely 

 reinstated during life. 



A nervous track, once marked out, will naturally have its resistance further 

 reduced if the discharges along it be repeated, and this is one way in which 

 tracks become permanent ; but the same condition may result from a single 

 strong discharge, especially in the case of immature organisms, since these 

 take the impress of a discharge more deeply than others. 



When two stimuli act simultaneously, each liberates energy along its 

 own track, and in so doing must lessen the resistance of the track and thus 

 open a path for energy liberated by the other stimulus. The consequence 

 is that the two become blended in consciousness and are perceived as parts 



