or states the entire meaning, or a part of the meaning, of the subject; and the proposition imparts no new information to those who already know the meaning of the subject. In the latter case, the proposition imparts new information, and the attribute connoted by the predicate is a real addition to that connoted by the subject. Thus the proposition "All men are rational" is verbal, because the attribute 'rationality' is a part of the larger attribute or group of attributes 'humanity,' while the proposition "All men are mortal" is real, because the attribute 'mortality' is not contained in the connotation of the subject 'man'; it is something different from, and new to, humanity; and the proposition expresses the conjunction of these two attributes.

§ 10. The Five Predicables: Genus, Species, Differentia, Proprium, and Accidens :—In a verbal proposition, the predicate, in relation to the subject, is either a genus, a species, or a differentia. In a real proposition, the predicate, in relation to the subject, is either a proprium, or an accidens. In other words, if the predicate of a proposition, in relation to the subject, be a genus, species, or differentia, the proposition is verbal, that is, the connotation of the predicate must be a part of that of the subject. If, on the other hand, the predicate be a proprium, or an accidens, the proposition is real, that is, the connotation of the predicate is not contained in that of the subject.

If the subject of a verbal proposition be an individual, the predicate, in relation to the subject, is called a species. If the subject be a class, the predicate, in relation to it, is called a genus, and the subject, in relation to the predicate, a species. The two terms, genus and species, are thus entirely relative to each other, and one has a meaning only in relation to the other. Given two terms related to each other as genus and species, the connotation of the latter minus the connotation of the former is equivalent to the differentia of the species, that is, to the attribute or group of attributes, which distinguishes that species from others belonging to the same genus. Thus the three terms genus, species, and differentia, implying each the other two, are correlatives. Further, just as a genus implies that there are

species under it, so a species implies that there are individuals under it. And so to the three correlatives mentioned above may be added another, namely, Individual; and the four terms may be thus defined :

A Genus in extension is a class including smaller classes or species. In comprehension, it is included in the species.

A Species in extension is a class which is included in a larger class or genus, and which includes individuals. In comprehension, it includes the genus and the differentia, and is included in the individual.

A Differentia is an attribute which distinguishes one species from others belonging to the same genus, and which is included in the comprehension of the species. In extension, that is, when taken as a general term, it includes the species and the individual.

An Individual is a particular thing or substance having a unique group of attributes, partly known and partly unknown. In extension, it is included in the species. In comprehension, it includes the species, and consequently also the differentia and genus. The connotation of a species=the connotation of the genus + the differentia.

.. The differentia=the connotation of the species – the connotation of the genus; and the connotation of the genus=the connotation of the species- the differentia. Example :-Taking 'animal' and 'man' as genus and species we have :—

=

Humanity Animality + the Differentia; .. the Differentia= Humanity - Animality.

But, Humanity = Animality+Rationality, that is, the connotation of man consists of those two attributes.

.. The Differentia = Animality + Rationality - Animality = Rationality. That is, 'rationality' is the differentia of the species 'man' in the relation to the genus 'animal,' and by the attribute 'rationality' the species 'man' is distinguished from others belonging to the same genus animal.' Similarly, an individual may have its differentia which is equivalent to the connotation of the individual minus that of the species:

Socraticity=Humanity+the Differentia; .. the Differentia

of Socrates Socraticity - Humanity.

By the Differentia of Socrates' is meant the group of attributes by which he is distinguished from other individuals belonging to the same species 'man.'

The differentia of a genus, like that of a species, in reference to a higher class, is the connotation of the genus minus the connotation of the higher class. Thus the differentia of 'animal' in relation to the higher class 'organic being' — animality — the attribute of being organized=sentiency; animal being defined as a sentient organized being.

=

In extension, a species is included in the genus, and an individual in the species. Thus 'animal' contains 'man'; and 'man' contains 'Socrates'; 'metal' contains 'gold'; 'organism' contains animal.' A differentia, when taken in extension, is a larger whole than the species. Sometimes, however, it coincides with the extension of the species; but the comprehension of the differentia being smaller than that of the species, its extent is theoretically greater than that of the latter.

The relation of individual, differentia, species, and genus may thus be represented by diagrams:

for man.

SOCRY

The inner circle

The outer circle for rational in the first diagram, and for animal in the second, the relation of animal and rational is shown in the third.

A Proprium (or property) of a genus, species, or individual is any attribute which follows from its comprehension either deductively or causally. If it follows from the comprehension of the genus, the property is called generic; if from that of the species, specific; and if from that of the individual object, individual. Thus, an individual thing may have its individual property, its specific property, or a property following from the species to which the individual belongs, and even a generic property following from the genus to which its species belongs. This last may be included in the specific property. A species may have two properties, one following from its differentia, and the other from its genus. The former is called the specific, and the latter the generic property, of the species; or both together are simply called its property. 'Memory,' for example, may be regarded as a property of man, following either from the genus animal, or from the differentia rational; 'power of judging' is likewise a property of man following from the differentia. The properties of the triangle, as proved in the Elements of Euclid, follow partly from the comprehension of its genus figure, partly from that of triangle, and partly from those of special kinds of triangles.

An Accidens (or accident) of an individual, genus, or species is any attribute which is possessed by it, and which does not follow from, or form a part of, its comprehension. If an accidens always belongs to an individual, or if it belongs to all the members of a genus, or species, it is called an inseparable accidens of that individual, genus, or species; as the place or date of birth of a particular person, the hair of man, the blackness of the crow, the whiteness of snow, &c. If, on the other hand, an accidens is sometimes present and sometimes absent in an individual, or if it belongs to a part only of a species or genus, then it is called a separable accidens of that individual, species, or genus; as the walking or sitting of a particular person, the wisdom of man, the solubility in water of salts, the opacity of gases, the learning of man, &c.

When the predicate of a proposition is a proprium, or an

accidens, of the subject, the latter in extension is included in the former, that is, the extension of the accidens or proprium, when taken as a general term, is a greater whole than that of the subject; while, in comprehension, the predicate expresses an attribute not contained in the connotation of the subject, that is, it imparts some new information about it; and the proposition, therefore, belongs to the class of real. In the proposition "Water boils at 100o C., under a pressure of 760 mm.," the attribute expressed by the predicate is not a part of the connotation of the term water.

The five terms-genus, species, differentia, proprium, and accidens are called predicables, because whatever may be predicated (affirmed) of a subject in a proposition is, in relation to the subject, one or other of the five. A predicable is thus a name of a class of predicates in relation to the subjects. It should be distinguished, on the one hand, from the word 'predicament,' or 'category,' which means a most general class of both subjects and predicates, and, on the other, from the word 'predicate,' which means what is affirmed or denied of a subject. Given a term: whatever be affirmed of it, the predicate, in relation to the subject, is a predicable, that is, it is either a genus, species, differentia, proprium, or accidens; and the subject as well as the predicate must belong to some category or other. Aristotle gave four predicables, viz., genus, definition, proprium, and accidens. Later logicians added 'species' and 'differentia to Aristotle's list, and removed 'definition' from it. Thus there came to be the five predicables we have explained above. Some logicians have made further additions to the list. Professor Fowler, for example, gives 'synonym,' 'definition,' 'designation,' idion (a Greek word signifying a peculiar property), in addition to the five, while others regard them as falling under one or other of the five predicables adopted by them: 'synonym' and 'designation,' for example, would be regarded by some of them as included in accidens, 'definition' as a compound of genus and differentia, and 'idion' as coming under either differentia or property.