IMITATION AMONG ATOMS AND ORGANISMS. 493 



the association of unlikes involves the utmost degree of resist- 

 ance. It follows that where unlikes are associated, the resistance 

 offered to their union will tend (1), where they are forcibly held 

 in association, to make them likes ; and (2) where they are free 

 to move, to dissociate them. This law of assimilation, as We may 

 briefly call it, finds illustration over so vast a field that it may 

 fairly be described as a universal character. 



If we begin, then, with the most complex of all the phenom- 

 ena known to us, our first illustrations will be drawn from the 

 realm of mind. The fact that cognition is a process of the associ- 

 ation of like and the dissociation of unlike impressions, and the 

 further fact that all the activities of thought, from reasoning of 

 the lowest to reasoning of the highest kind, involve the association 

 of like and dissociation of unlike elements these are psycho- 

 logical truths of the utmost certainty. At the outset of all know- 

 ing is the indispensable condition that unless we can connect the 

 thing perceived with some other things already known, and thus 

 recognize our object as a like of those things, we can not know it 

 at all, and it can not become a part of our store of mental experi- 

 ences; while the very act by which we know it involves dissoci- 

 ation of it as an impression from all the impressions which it 

 does not resemble. From this, the simplest form of knowing, to 

 the most elaborate process of the reasoning faculty; from the 

 recognition of single objects as like others to the recognition of 

 classes of objects as like other classes ; from the discovery of a 

 causal relation between one set of objects or changes that is like 

 the causal relation between another set of objects or changes to 

 the discovery of the causal likeness connecting great groups of 

 objects and activities, and finally all objects and changes whatso- 

 ever, there is throughout the same process at work the process 

 of the association of likes and the dissociation of unlikes that 

 conditions the mode of all our mental operations. So-called 

 thought or reflection, for example, is simply the recovery into 

 consciousness, for the purposes of knowledge, of cognitions more 

 or less simple, more or less complex ; cognitions recoverable as 

 images, symbols, or terms from the classes in which they have 

 been first associated by the mind ; and the sense of pleasure felt 

 by a thinker in discovering analogies can spring only from satis- 

 faction of the demand, even in mental processes, that likes shall 

 be brought together and unlikes separated. Classification in all 

 its forms, whether in the ordinary business of life, as a means to 

 scientific investigation, or for the ends of philosophic thought, 

 illustrates the same necessity : at first unlikes and likes are 

 mingled indiscriminately, and at first the mind regards them, if 

 roughly, as being alike ; but a sense of unrest leads to further 

 examination of the aggregated elements until, by a more con- 



