7 8 THE SCIENCE OF LOGIC. 



The largest and widest class in any scheme of classification is 

 called the summum genus (76^09 yeviKcorarov) in regard to that order 

 or department of things ; 1 and in a classification of all knowable 

 things it would be a summum genus not relatively to any particu 

 lar department, but in an absolute sense. 2 At the other end of the 

 scale is the lowest species, below which there are no sub-classes 

 but only individuals. This is called the infima species (elSo? 

 elSiKwrarov). The direct series of classes between any infima 

 species and its summum genus is called a predicamental line linea 

 praedicamentalis. As every genus must have at least two species 

 under it, it is plain that every summum genus must give rise to 

 numerous lines or trees of division (called predicamental lines) 

 branching off progressively towards its various infime species. In 

 every such line the class next above any given class is called the 

 proximate genus (genus proximu m) of the latter ; that next below it 

 its proximate species (species proximo). A subaltern genus genus 

 subalternum (ryez/o? a-vvd\\n\ov) is one which has other genera 

 (at least one) both above and below it. Similarly, a subaltern 

 species species subalterna is one which has at least one other 

 species above and below it In every predicamental line the genera 

 which lead down progressively from the summum genus to any 

 given class, are said to be the cognate genera of that class. Thus, 

 &quot; substance,&quot; &quot;matter,&quot; &quot;organism,&quot; &quot;animal,&quot; would be the 

 cognate genera of &quot; man &quot;. The co-ordinate classes into which 

 any genus is divided are called cognate species of that genus. 

 Thus, &quot; equilateral,&quot; &quot; isosceles &quot; and &quot; scalene,&quot; are cognate 

 species of the genus &quot; triangle &quot;. 



Porphyry s Tree : Among all the classifications of the objects 

 of human knowledge the one which has most interest for us, and 

 which is in many ways the most important, is that in which we 

 ourselves, individual human beings, appear as members. The 

 predicamental line commencing with &quot; substance &quot; one of Aris 

 totle s summa genera, and ending with &quot; man &quot; as infima species, 

 was first drawn up by Porphyry, and has been used ever since to 

 illustrate the relations, explained above, between genera, species, 

 and individuals. It is referred to generally as the tree of Porphyry, 

 or Porphyry s tree, less frequently as the Ramean tree (from Ramus, 

 a sixteenth century logician). 



1 &quot; Man &quot; for the science of anthropology ; &quot; animal &quot; for zoology ; &quot; plant &quot; 

 for botany; &quot; living organism &quot; for biology. 



2 We shall deal with the tenfold scheme of Pradimenta or Categories attempted 

 by Aristotle, and other similar schemes in this sense, in Chapter V. 



