CLASSIFICATION. 433 



cation, in reference to tlicse pui-poses, may be stated as ft)llo\vs : To 

 provide that tilings shall be thought of in such groups, and those gTOups 

 m such an order, as ^vill best conduce to the remembrance and to tlie 

 ascertainment of tlieir laws. 



Classification thus considered, diffei-s from classification in the wider 

 sense, in having rcfei'cnce to real objects exclusively, and not to all 

 that are imagijuible : its object being the due coordination in oui' minds 

 of those things only, wth tlic properties of which wc have actually , 

 occasion to make ourselves acquainted. But on the other hand it em- 

 braces all really existing objects. We cannot constitute any one class 

 properly, exce^Jt in reference to a general division of the whole of 

 natui-e; we cannot determine the group in which any one object can 

 most conveniently be placed, without taking into consideration all the 

 varieties of existing objects, all at least which have any degree of affinity 

 with it. No one family of plants or animals could have been rationally 

 constituted, except as part of a systematic aiTangcment of all plants or 

 animals; nor could such a general an-angemcnt have been properly 

 made, without first determining the exact place of plants and animals 

 in a general division of nature. 



The theory of scientific classification, in its most general aspect, is 

 now very well understood, owing chiefly to the labors of the distin- 

 guished natm^alists to whom science is indebted for what are called 

 Natural An-angements or Classifications, especially of the organized 

 world. jMr. Whewell, in his Philosoj^hij of the Inductive Sciences, has 

 systematized a portion of the general logical principles which these 

 classifications exemplify ; and this has been still more completely done 

 by M. Comte, whose view of the philosophy of classification, in the 

 third volume of his great work, is the most complete wath which I am 

 acquainted. 



§ 2. There is no property of objects which may not be taken, if we 

 please, as the foundation for a classification or mental gi-oujjing of 

 those objects ; and in our first attempts we are liko-ly to'select for that 

 purpose properties which are simple, easily conceived, and perceptible 

 on a first view, without any previous process of thought. Thus Tour- 

 nefort's aiTangemont of plants was founded on the shape and divisions 

 of the corolla; and that which is commonly called the Linnaean (though 

 Linnaeus also suggested another and more scientific an-angeraent) was 

 grounded chiefly upon the nimiber of the stamens and pistils. 



But these classifications, which are at first recommended by the 

 facility they afford of ascertaining to what class any individual belongs, 

 are seldom much adapted to the ends of that Classification which is 

 the subject of our present remarks. The Linntean arrangement an- 

 swers the j)uii)06e of making us think together of all those kinds of 

 plants which possess the same number of stamens and j)istils ; but to 

 think of them in that manner is of little use, since we seldom have 

 anything to affinn in common of the plants which have a given number 

 of stamens and pistils. If plants of the class Pentandria, order .Mono- 

 gynia, agreed in any other properties, the habit of thhiking and speak- 

 ing of the plants under a common designation would conduce to our 

 remembering those common properties so far as they were ascertained, 

 and would dispose us to be on the look-out for such of them as are not 

 yet known. But since this is not the case, the only purpose of thought 

 31 



