436 OPERATIONS SUBSIDIARY TO INDUCTION. 



manner similar to other fishes. A plea that human laws which mention 

 fish do not apply to whales, would be rejected at once by an intelligent 

 judge."* 



These different classifications are all good, for the purposes of their 

 own particular departments of knowledge or practice. But when we 

 are studying objects not for any special practical end, but for the sake 

 of extending our knowledge of the whole of their properties and rela- 

 tions, we must consider as the most important attributes, those which 

 contribute most, either by themselves or by their eft'ects, to render the 

 things like one another, and unlike other things ; which give to the class 

 composed of them the most marked individuality ; whicli fill, as it were, 

 the largest space in their existence, and would most impress the atten- 

 tion of a spectator who knew all their properties but was not specially 

 interested in any. Classes fbrmed upon this principle may be called, 

 in a more emjihatic manner than any others, natural groups. 



§ 3. On the subject of these groups Mr. Wliewell lays down a theo- 

 ry, grounded on an important truth, whicli he has, in some respects, 

 expressed and illustrated very felicitously; but also, as it appears to 

 me, with some admixture of error. It will be advantageous, for both 

 these reasons, to extract the statement of his doctrine in the very 

 words he has used. 



" Natural groups," according to Mr. Whewell,t are " given by 

 Type, not by Definition." And this consideration accounts for " that 

 indefiniteness and indecision which we frequently find in the descrip- 

 tions of such gi-oups, and which must appear so strange and incon- 

 sistent to any one who does not suppose these descriptions to assume 

 any deeper ground of connexion than an arbitrary choice of the 

 botanist. Thus in the family of the rose-tree, we are told that the 

 ovules are very rarely erect, the stigmata usually simple. Of what 

 use, it might be asked, can such loose accounts be 1 To which the 

 answer is, that they are not inserted in order to distinguish the species, 

 but in order to describe the family, and the total relations of the ovules 

 and the stigmata of the family are better known by this general state- 

 ment. A similar obsei-vation may be made with regard to the Anom- 

 alies of each gi'oup, which occur so commonly, that Mr. Lindley, in his 

 Introduction to the Natural System of Botany, makes the 'Anomalies' 

 an article in each family. Thus, part of the chairacter of the Rosacege 

 is, that they have alternate stipulate leaves, and x\\?it the alhumen is 

 obliterated ; but yet in Lowea, one of the genera of this family, the 

 stipulae are absent; and the albumen is present in another, Neillia. 

 This irnplies, as we have already seen, that the artificial character (or 

 diagnosis, as Mr. Lindley calls it), is imperfect. It is, though very 

 nearly, yet not exactly, commensurate with the natural gi'oup : and 

 hence in certain cases this character is made to yield to the general 

 weight of natural ' affinities. 



" Tliese views, — of classes determined by characters which cannot 

 be expressed in words, — of propositions which state, not what hap- 

 pens in all cases, but only usually, — of particulars which are included 

 in a class, though they transgress the definition of it, may probably 



* Aphorisms concerning the Language of Science, in Mr. Whewell's Philosophy of the 

 Inductive Sciences, vol. i., p. Ixxv. 

 ■t Phil. Ind. Sc, i., 476-7. 



