It must be allowed that a predication, or proposition, is intended to mark some portion of the order either of our sensations or of our ideas, i.e., some part of the coexistences or sequences which take place either in our minds, or in what we term the external world. But what sort of order is it that a predication marks? An order supposed to be believed in. When John, or man, are said to be marks of an individual object, all there is in the matter is that these words, being associated with the idea of the object, are intended to raise that idea in the mind of the person who hears or reads them. But when we say, John is a man, or, John is an old man, we intend to do more than call up in the hearer’s mind the images of John, of a man, and of an old man. We intend to do more than inform him that we have thought of, or even seen, John and a man, or John and an old man, together. We inform him of a fact respecting John, namely, that he is an old man, or at all events, of our belief that this is a fact. The characteristic difference between a predication and any other form of speech, is, that it does not merely bring to mind a certain object (which is the only function of a mark, merely as such); it asserts something respecting it. Now it may be true, and I think it is true, that every assertion, every object of Belief,—everything that can be true or false—that can be an object of assent or dissent—is some order of sensations or of ideas: some coexistence or succession of sensations or ideas actually experienced, or supposed capable of being experienced. And thus it may appear in the end that in expressing a belief, we are after all only declaring the order of a group or series of sensations or ideas. But the order which we declare is not an imaginary order; it is an order believed to be real. Whatever view we adopt of the psychological nature of Belief, it is necessary to distinguish between the mere suggestion, to the mind of a certain order among sensations or ideas such as takes place when we think of the alphabet, or the numeration table and the indication that this order is an actual fact, which is occurring, or which has occurred once or oftener, or which, in certain definite circumstances, always occurs; which are the things indicated as true by an affirmative predication, and as false by a negative one.
That a predication differs from a name in doing more than merely calling up an idea, is admitted in what I have noted as the second half of the author’s theory of Predication. That second half points out that every predication is a communication, intended to act, not on the mere ideas of the listener, but on his persuasion or belief: and what he is intended to believe, according to the author, is, that of the two names which are conjoined in the predication, one is a mark of the same idea (or let me add, of the same sensation or cluster of sensations) of which the other is a mark. This is a doctrine of Hobbes, the one which caused him to be termed by Leibnitz, in words which have been often quoted, “plus quam nominalis.” It is quite true that when we predicate B of A—when we assert of A that it is a B—B must, if the assertion is true, be a name of A, i.e., a name applicable to A; one of the innumerable names which, in virtue of their signification, can be used as descriptive of A: but is this the information which we want to convey to the hearer? It is so when we are speaking only of names and their meaning, as when we enunciate a definition. In every other case, what we want to convey is a matter of fact, of which this relation between the names is but an incidental consequence. When we say, John walked out this morning, it is not a correct expression of the communication we desire to make, that “having walked out this morning” or “a person who has walked out this morning” are two of the innumerable names of John. They are only accidentally and momentarily names of John by reason of a certain event, and the information we mean to give is, that this event has happened. The event is not resolvable into an identity of meaning between names, but into an actual series of sensations that occurred to John, and a belief that any one who had been present and using his eyes would have had another series of sensations, which we call seeing John in the act of walking out. Again, when we say, Negroes are woolly-haired, we mean to make known to the hearer, not that woolly-haired is a name of every negro, but that wherever the cluster of sensations signified by the word negro, are experienced, the sensations signified by the word woolly-haired will be found either among them or conjoined with them. This is an order of sensations: and it is only in consequence of it that the name woolly-haired comes to be applicable to every individual of whom the term negro is a name.
There is nothing positively opposed to all this in the author’s text: indeed he must be considered to have meant this, when he said, that by means of substituting one name for another, a predication marks the order of our sensations and ideas. The omission consists in not remarking that what is distinctively signified by a predication, as such, is Belief in a certain order of sensations or ideas. And when this has been said, the Hobbian addition, that it does so by declaring the predicate to be a name of everything of which the subject is a name, may be omitted as surplusage, and as diverting the mind from the essential features of the case. Predication may thus be defined, a form of speech which expresses a belief that a certain coexistence or sequence of sensations or ideas, did, does, or, under certain conditions, would take place: and the reverse of this when the predication is negative.—Ed.
162 For the more complete elucidation of this important part of the business of Naming, it is necessary to 163 remark, that Logicians have classed Predications, under five heads; 1st, when the Genus is predicated, 164 of any subject; 2dly, when the Species is predicated; 3dly, when the Specific Difference is predicated; 4thly, 165 when a Property is predicated; 5thly, when an Accident is predicated. These five classes of names, the things capable of being predicated, are named PREDICABLES. The five Predicables, in Latin, the language in which they are commonly expressed, are named Genus, Species, Differentia, Proprium, Accidens.
We have already seen, perhaps at sufficient length, the manner in which, and the end for which, the Genus, and the Species are predicated of any subject. It is, that the more comprehensive name, may be substituted for the less comprehensive; so that each of our marks may answer the purpose of marking, to as great an extent as possible. In this manner we substitute the word man, for example, for the word Thomas, when we predicate the Species of the individual, in the proposition, “Thomas is a man;” the word animal, for the word man, when we predicate the Genus of the Species, in the proposition, “man, is an animal.“[49]
[49] If what has been said in the preceding [note] is correct, it is a very inadequate view of the purpose for which a generic or specific name is predicated of any subject, to say that it is in order that “the more comprehensive name may be substituted for the less comprehensive, so that each of our marks may answer the purpose of marking to as great an extent as possible.” The more comprehensive and the less comprehensive name have each their uses, and the function of each not only could not be discharged with equal convenience by the other, but could not be discharged by it at all. The purpose, in predicating of anything the name of a class to which it belongs, is not to obtain a better or more commodious name for it, but to make known the fact of its possessing the attributes which constitute the class, and which are therefore signified by the class-name. It is evident that the name of one class cannot possibly perform this office vicariously for the name of another.—Ed.
166 We have already, also, taken notice of the artifice, by which smaller classes are formed out of larger, by the help of secondary marks. Of these secondary marks, the principal classes are designated by the terms Differentia, Proprium, Accidens. No very distinct boundaries, are, indeed, marked by these terms; nor do they effect a scientific division; but, for the present purpose, the elucidation of the end to which Predication is subservient, they are sufficient.
Differentia is always an Attributive, applicable to a Genus, and which, when combined with it, marks out a Species; as the word rational, which is applicable to the Genus animal, and when applied to it, in the phrase “rational animal,” marks out a Species, and is synonymous with the word man. In a similar manner the word sensitive is applicable to body, and marks out the subordinate Genus, animal.
Proprium is also an Attributive, and the Attributives classed under this title differ from those classed under the title differentia, chiefly in this; That those classed under differentia, are regarded as more expressly involved in the definition of the Species which they seem to cut out from the Genus. Thus, both rational, and risible, when applied to animal, cut out of it the class Man; but rational is called DIFFERENTIA, risible PROPRIUM, because rational, is strictly involved in the definition of man; risible is not. Some Attributives are classed under the title proprium, which, when applied to the genus, do not constitute the same Species, constituted by the differentia, but a different Species; as bipes, two-footed animal, is the name of a class including at least the two classes of men, and birds; hot-blooded animal, is the name of a class so 167 large as to include man, horse, lion, dog, and the greater part of the more perfectly organized Species. There are some Attributives, classed under the title proprium, which cut out of the Genus a class even less than that which is cut by the differentia; as, for example, the word grammatical. This word grammatical, applied to the word animal, in the term “grammatical animal,” separates a class so small, as to include only part of the Species man, those who are called Grammarians. Such Attributives, for an obvious reason, are applicable, as well to the name of the Species, as to that of the Genus. Thus, we say, “a grammatical man,” as well as “a grammatical animal,” and that with greater propriety, as cutting out the sub-species from the Species more immediately.
The Attributives, classed under the title accidens, are regarded, like those classed under differentia, and proprium, as applicable to the class cut out by the differentia, but applicable to it rather fortuitously than by any fixed connection. The term lame is an example of such Attributives. The term lame, however, applied to the name of the Species, does not the less take out of it a sub-species, as “lame man,” “lame horse.”