32 SOME THOUGHTS ON CLASSIFICATION 



two of them must either be the same repeated, or different. Simi- 

 larity is likeness in some particulars or to a certain extent without 

 complete identity, and therefore necessarily connotes divisibility into 

 parts or complexity of nature. Our knowledge of what we call an 

 external object consists in a certain set of sensations, uniformly arising 

 from what we express by its presence, and connected together in our 

 minds as shown by experience always to be derivable from it. The 

 remembrance or thought of this object in the mind when it is no 

 longer present is a complex state consisting of the separate remeni" 

 brances or revivals of the various sensations received from the object, 

 associated together from their having been received together, and that 

 as often as the object was offered to the senses. Now suppose the 

 mind to be conscious, simultaneously or in immediate succession, of 

 two or more objects, each having its own qualities, or in other words, 

 producing its own cluster of sensations, if any one distinct sensation 

 should be alike in both or all of them, this common part in the 

 respective clusters of sensations or correspondent ideas will associate 

 together the separate clusters as having something common, which is 

 precisely what we mean when we affirm resemblance or likeness of 

 objects. It is possible that several objects notwithstanding abundant 

 differences may agree together in several points which, of course, makes 

 the resemblance stronger, and we can conceive of all degrees, from 

 correspondence in one element only, up to such an agreement in all 

 particulars as would constitute sameness, the objects differing only in 

 time and place of being offered to the senses. We th\is see how it 

 is that single sensations or simple ideas, occurring at different times, 

 may be the same or different ; but no resemblance can be predicated 

 of those that differ, whilst as objects may be made up of various parts 

 and may cause various sensations, it is therefore possible that some 

 part or some one or more sensations may be the same, as a part or 

 some sensations belonging to a different object causing the two to 

 resemble each other more or less. The mind which is conscious of 

 the sensations, if they have much vividness or direct relation to our 

 enjoyment or suffering, necessarily becomes conscious also of the 

 resemblance, and associating together the objects by what is common 

 to them, considers them together, and if occasion should arise, lan- 

 guage applies to them a common name. Their differences are not 

 overlooked ; they are not supposed to be the same, but they resemble 

 one another in certain points, which engage our attention, there being 



