90 NAMES AND mOPOSITIONS. 



Proprium, continue the sclioolmeri, is predicated accidentally, indeed, 

 but necessarily; or, as tliey further explain it, signifies an attribute 

 which is not indeed part of the essence, but which flows fi-om, or is a 

 consequence of, the essen'ce, and is, therefore, inseparably attached to 

 the species ; e. g., the various properties of a ti'iangle, which, though 

 no part of its definition, must necessarily be possessed by whatever 

 comes under that definition. Accidens, on the contrary, has no con- 

 nexion whatever with the essence, but may come and go, and the 

 species still remain what it was before. If a species could exist 

 without its Propria, it must be capable of existing without that upon 

 which its Propria are necessarily consequent, and therefore without its 

 essence, without that which constitutes it a species. But an Accidens, 

 whether separable or inseparable from the species in actual experience, 

 may be supposed separated, without the necessity of supposing any 

 other alteration ; or at least, without supposing any of the essential 

 properties of the species altered, since with them an Accidens has no 

 connexion. 



A Proprium, therefore, of the species, may be defined, any attribute 

 which belongs to all the individuals included in the species, and which, 

 although not connoted by the specific name (either ordinarily if the 

 classification we are considering be for ordinary purposes, or specially 

 if it be for a special purpose), yet follows from some attribute which 

 the name either ordinarily or specially connotes. 



One attribute may follow from another in two ways ; and there are 

 consequently two kinds of Proprium. It may follow as a conclusion 

 follows premisses, or it may follow as an effect follows a cause. Thus, 

 the attribute of having the opposite sides equal, which is not one of 

 those connoted by the word Parallelogi'am, nevertheless follows from 

 those connoted by it, namely, from having the opposite sides straight 

 lines, and parallel, and the number of sides four. The attribute, 

 therefore, of having the opposite sides equal, is a Proprium of the 

 class parallelogram ; and a Proprium of the first kind, which follows 

 from the connoted attributes by way of demonstration. The attribute 

 of being capable of understanding language is a Proprium of the 

 species num, since, without being connoted by the word, it follows 

 from an atti'ibute which the word does connote, viz., from the attribute 

 of rationality. But this is a Proprium of the second kind, which fol- 

 lows by way of causation. How it is that one property of a thing 

 follows, or can be inferred from another ; under what conditions this 

 is possible, and what is the exact meaning of the phrase ; are among 

 the questions which will occupy us in the two succeeding Books. At 

 present it needs only be said, that whether a Proprium follows by 

 demonstration or by causation, it follows necessarily ; that is to say, it 

 cannot hut follow, consistently with some law which we regard as a 

 part of the constitution either of our thinking' faculty or of the universe. 



§ 8. Under the remaining predicable, Accidens, are included all 

 attributes of a thing which are neither involved in the signification of 

 the name (whether ordinarily or as a term of art), nor have, so far as 

 we know, any necessary connexion with attributes which are so in- 

 volved. They are commonly divided into Separable and Inseparable 

 Accidents. Inseparable accidents are those which — although we know 

 of no connexion between them and the attributes constitutive of the 



