The Essential Predicables - 3.6 - Notes on "The Reasonable Person" by Mark Grannis

Predication in General 

"Predicables" refer to what can be said or attributed to a subject. 

Take a sentence, for example. "The dog is yellow."

Dog is the subject. 

Yellow is the predicate. 

The verb to be is the copula which unites them. 

And so of the things that can be said of a subject there are five categories by which one can use predication: Genus, species, difference, property, and accident. Grannis treats genus, species, and difference in this subchapter. 

Genus - They don't have corresponding individuals in reality 

"Genus: a predicable that extends to many things by virtue of an essential nature they share, but which does not state the whole essence of the subject." When predicating a genus one is attributing to the subject a grouping which is larger than their own species, and thus describes the umbrella within which that species falls, but not the fullness of what the subject's species is. For example, man is an animal. Man certainly is a type of animal as that is the broader grouping of creatures that man is a part of, but just "animal" doesn't specify the fullness of what a man is, only part. One way to tell if something is functioning as a genus is to ask if it corresponds to real existing things. For example, there is no real "animal" as such that exists, and thus we can see that we are missing a complete definition of a thing. There is not a relationship between a universal and inferior. 

Species - They do have corresponding individuals in reality 

"Species: a predicable that extends to many things that differ only non-essentially and numerically, and which states the whole essence of the subject." Species, on the other hand, is the fitting expression of what the subject is, of its identity. Thus, we can find real examples of the species and there is a relationship between universal and inferior. For example, we can speak of a species "lion" and there are actual real lions. And so species will be the adequate definition of what a thing is. For example, a gun is a weapon that shoots bullets. The species will contain the larger grouping of genus that the thing belongs to, but then a specific difference which makes it to be a particular species in that genus which actually exists. 

Difference - The quality that contracts 

"Difference: a predicable that provides the basis for contracting a genus into a species or into an inferior genus by identifying the proper and determining part of the essence." "Specific difference is a difference that contracts a genus into a species." "A Generic difference is a difference that contracts a genus into an inferior genus." Just as a genus only expresses the broader grouping that the species belongs to, the difference only expresses the unique quality which sets this species apart from others. For example, "man is rational". Rational is not a complete definition of man, but only the quality that sets him apart from other animals. And so we can say that a difference is a quality that either contracts a genus into a smaller genus or a genus into a species. 

Practice Examples

a) A triangle is a polygon - the predicate is a genus because polygon is not a complete definition and is broader than triangle, thus must be a genus. 

b) Regicide is murder - the predicate is a genus because murder is not a complete definition and is broader than regicide, thus must be a genus. 

c) A triangle is a polygon with three sides - the predicate is a species because it includes an adequate definition by expressing its broader grouping - polygon - and its specific difference that makes it a triangle - having three sides. 

d) Regicide is the murder of a king or queen - Same as c. 

e) Purple is a color - Same as a.

f) Patience is a virtue - Same as a, b, and e.

g) Purple is midway between red and blue - specific difference because it is not a complete definition, but is a quality that specifically makes purple to be purple. 

h) Predicables are relations between terms - species because same as b

i) Men are often hot-tempered - Generic difference because this is not expressed as a genus, not a definition, nor as the specific difference that makes man, man, and so it must be a generic difference.