24 On Property
On Property because then it would be indistinguishable from the species. It signifies either a part of the thing or something extrinsic to it. But it does not signify anything extrinsic; otherwise, it would be a property or an accident. The only remaining possibility is that it signify a part of the thing. The difference then always expresses a part of the thing in the way that white expresses whiteness. Consequently the difference always is (or ought to be) concrete in form, and corresponding to it (in the way that whiteness corresponds to white), there should be an abstract term which directly signifies the relevant part of the thing. Thus, the abstract term should always supposit for a part and the concrete term for the whole composed of that part and some other part.
It is clear that the difference is predicated in quale, for by the difference one does not respond to the question 'What is it?' but to the question 'How is it qualified?' For if it should be asked 'How is man qualified?' an appropriate response would be that he is rational or material. Thus, the differentia is predicated in quale. It is predicated of the same items as the species because it is convertible with the species. Thus, one should not claim that soul is the difference of body, but rather besouled. Similarly it is not reason that is the difference of man, but rational.
24: On Property Next we shall examine the notion of property. The term 'property' has four senses. In one sense we say that a property is something that belongs to one species or one genus but which, nevertheless, need not belong to all things subsumed under that species or genus. The common term grammatical is said to be a property of man because it belongs only to men. It does not, however, belong to every man; for not every man is grammatical. Similarly, to move by progressive motion is said to be proper to animal since it does not belong to any thing but animals, nevertheless, it does not belong to every animal.
In a second sense a property is something which belongs to every particular of some particular species, but not only to that species. One might say that biped is a property of man.
In a third sense a property is one which belongs to some species taken universally, but not at all times. It belongs to a particular at one time, but not at another. Thus, if every man were to turn grey in his old age, then to turn grey in this sense would be a property of man.
In the fourth sense a property is anything which belongs to some common notion taken universally, to no other notion, and to all of the items subsumed under the notion, with the consequence that the property is convertible with that common notion and necessarily predicable of the notion for as long as existence can be predicated of it. It is in this sense that the notion of a property is said to be one of the five universals. The other three senses are included under the notion of accident. Thus, risible is a property of man; for it belongs to every man, only to men, and always to men. God could not create a man without making him risible for the man would truly be able to laugh. There would not be anything contradictory in the man's laughing. He would be risible, for that is what we mean by 'risible'. Risible, then, is a property of man. Laughing however, is not a property of man; it is an accident. The two predicables laughing and risible are not one and the same. They differ in that one is affirmed of something of which the other is denied.
Included in this fourth sense of 'property' are such passions as belong not only to more general notions but also to their logical inferiors. Every property is the property of something, but it is not the property ofjust anything. Thus, a passion of a genus is predicated of the species, but it is not the property of the species.
It should be noted that a property is not something really inhering in that of which it is the property; for then it would not be a universal, nor belong to something universally taken, nor be predicated of many.
A property, then, does not inhere in the subject whose property it is said to be. It need not even designate an absolute thing inhering in that which is designated by the subject. Sometimes it designates a thing distinct from and extrinsic to the entity designated by the subject. Sometimes it designates this thing affirmatively and sometimes negatively. Properties designating affirmatively an extrinsic entity are heat-producing, creative, and the like. Thus, heat-producing does not designate a thing inhering in that which is heat-producing; it designates on the contrary something which can be produced by it. (Here, I am speaking of the first subject of heat-producing.)
Likewise, creative does not designate a thing inhering in God; it designates something that can be produced by God. Negative properties are immortal, incorruptible, immaterial, etc.
Nevertheless, some properties designate things inhering in or capable of inhering in that which is designated by the subject; the following passions are of this sort: alterable, capable ofbeing heated, beautifiable, capable ofbecoming white.
Secondly, it should be noted that every affirmative proposition which is not equivalent to a negative proposition and in which a property is predicated is equivalent to a proposition expressing possibility. If the relevant proposition were not equivalent to a proposition expressing possibility, then the proposition