374 FUNCTIONS OF THE NERVOUS SYSTEM. 



ideas, however, being most evident in some minds, whilst the tendency to the 

 modification of them is more obvious in others. The latter is one source of 

 that faculty, to which the term Imagination is given. 



493. The Mind, however, is not restricted to external sources, for objects 

 of perception ; since, when once in activity, it perceives its own operations, 

 and traces the various relations and connections among its objects of thought. 

 The power of doing this may be termed Internal Perception. The mind 

 often has internal perceptions without any direct effort of the will, just as it 

 receives perceptions from external objects ; but its power of cognizance is not 

 unfrequently directed inwards by express volition; and the act is then pecu- 

 liarly termed Reflection, or perhaps better, Introspection. Now by this pro- 

 cess, a new class of ideas is excited, of a very different character from those 

 which are called up by external objects ; and these, being entirely dependent 

 upon the operation of the Intellectual powers, and having no dependence upon 

 Sensations except as the original springs of those operations, may be termed 

 Intellectual Ideas, in contradistinction to the Sensational Ideas. The former, 

 like the latter, become the subjects of the Associating tendency; and thus are 

 combined in Trains of Thought. Some of these intellectual ideas appear to 

 be so necessarily excited by mental operations, even of the simplest kind, and 

 to be so little dependent on individual peculiarities either inherent or acquired, 

 that they take rank as fundamental axioms or principles of Human Thought. 

 Such are, the belief in our own present existence, or the faith which we re- 

 pose in the evidence of Consciousness ; this idea being necessarily associated 

 with every form and condition of mental activity, the belief in our past ex- 

 istence, and in our personal identity so far as our memory extends, which is 

 necessarily connected with the act of Recollection ; with this, again, is con- 

 nected the general idea of Space: the belief in the external and independent 

 existence of the causes of our sensations, which results from Perception, or 

 the direction of the mind to the ideas originating in them ; with this is con- 

 nected the general idea of Space : the belief in the existence of an efficient 

 cause for the changes which we witness around us, which springs from the 

 Perception of those changes ; whence is derived our idea of Power, the be- 

 lief in the stability of the order of nature, or in the invariable sequence of 

 similar effects to similar causes, which also springs directly from the Percep- 

 tion of external changes, and seems prior to all reasoning upon the results of 

 observation of them (being observed to operate most strongly in those whose 

 experience is most scanty, and in relation to subjects that are perfectly new 

 to them) ; but which is the foundation of all applications of our own experience 

 or that of others, to the conduct of our lives, or to the extension of our know- 

 ledge : lastly, the belief in our own free tcill, involving the general idea of 

 Voluntary Power ; which is in like manner a direct result of our Internal 

 Perception of those mental changes which are excited by sensations. Hence 

 it is evident, that " the only foundation of much of our belief, and the only 

 source of much of our knowledge, is to be found in the constitution of our own 

 minds ;" but it must be steadily kept in view, that these fundamental axioms 

 are nothing else than expressions of the general fact, that the ideas in question 

 are uniformly excited (in all ordinarily-constituted minds, at least) by simple 

 attention to the changes in which they originate. 



494. Upon the Sensational and Intellectual Ideas thus brought under the 

 cognizance of the Mind, all acts of reasoning are founded. These consist, 

 for the most part, in the aggregation and collocation of ideas ; the decompo- 

 sition of complex ideas into more simple ones, and the combination of simple 

 ideas into general expressions ; in which are exercised the faculty of Com- 

 parison, by which the relations and connections of ideas are perceived, that 



