386 THE PRINCIPLES OF SCIENCE. 



the series of English writings which have, in the present 

 century, made logic a new and progressive science. In 

 Table IV. Bentham gives the Arbor Porphyriana, as 

 exhibited in the course of a college lecture in 1761, call- 

 ing it the original form. His reading of logic seems to 

 have been restricted to the compendiums of Saunderson 

 and Watts, and it was only after the text was written that 

 he obtained an opportunity of consulting the work of 

 Porphyry, and was surprised to find no diagram therein. 

 He attributes its invention to Peter Ramus, although he 

 had never seen the writings of that logician, and had 

 merely learnt their titles from a dictionary. 



In this essay he states in the most powerful way the 

 advantages of the bifurcate method of classification, which 

 had been suggested to him by a chapter in Saunderson's 

 logic and the diagram given in the college course. 

 Although the Tree of Porphyry and the principles of 

 bifurcation had been mentioned by almost all logicians, 

 the utility and excellence of the method, he says (p. 287), 

 had not made itself apparent. Indeed the method was 

 mentioned but to be slighted, or to be made a subject of 

 pleasantry by Reid and Kames. Bentham sufficiently 

 states his own opinion when he speaks (p. -295) of 'the 

 matchless beauty of the Eameaii Tree.' After fully show- 

 ing its logical value as an exhaustive method of classifi- 

 cation, and refuting the objections of Reid and Kames, 

 on a wrong ground, as I think, he proceeds to inquire to 

 what length it may be carried. He correctly points out 

 two objections to the extensive use of bifid arrangements, 

 (i) because v they soon become impracticably extensive and 

 unwieldy, and (2) because they are uneconomical. In his 

 day the recorded number of different species of plants 

 was 40,000, and he leaves the reader to estimate the im- 

 mense number of branches and the enormous area of a 

 bifurcate table which should exhibit all these species in 



