We have seen that in the several mental processes which are grouped together under the general head of Understanding, the stage or step of Abstraction is first; following which is the second step or phase, called Generalization or Conception. The third step or phase is that which is called Judgment. In the exercise of the faculty of Judgment, we determine the agreement or disagreement between two concepts, ideas, or objects of thought, by comparing them one with another. From this process of comparison arises the Judgment, which is expressed in the shape of a logical Proposition. A certain form of Judgment must be used, however, in the actual formation of a Concept, for we must first compare qualities, and make a judgment thereon, in order to form a general idea. In this place, however, we shall confine ourselves to the consideration of the faculty of Judgment in the strictly logical usage of the term, as previously stated.
We have seen that the expression of a concept is called a Term, which is the _name_ of the concept. In the same way when we compare two terms (expressions of concepts) and pass Judgment thereon, the expression of that Judgment is called a Proposition. In every Judgment and Proposition there must be two Terms or Concepts, connected by a little word “is” or “are,” or some form of the verb “to be,” in the present tense indicative. This connecting word is called the Copula. For instance, we may compare the two terms _horse_ and _animal_, as follows: “A horse is an animal,” the word _is_ being the Copula or symbol of the _affirmative_ Judgment, which connects the two terms. In the same way we may form a _negative_ Judgment as follows: “A horse is not a cow.” In a Proposition, _the term of which something is affirmed_ is called the Subject; and _the term expressing that which is affirmed of the subject_ is called the Predicate.
Besides the distinction between affirmative Judgments, or Propositions, there is a distinction arising from _quantity_, which separates them into the respective classes of _particular_ and _universal_. Thus, “_all_ horses are animals,” is a _universal_ Judgment; while “_some_ horses are black” is a particular Judgment. Thus all Judgments must be either _affirmative_ or _negative_; and also either _particular_ or _universal_. This gives us four possible classes of Judgments, as follows, and illustrated symbolically:
1. Universal Affirmative, as “All A is B.”
2. Universal Negative, as “No A is B.”
3. Particular Affirmative, as “Some A is B.”
4. Particular Negative, as “Some A is not B.”
The Term or Judgment is said to be “_distributed_” (that is, extended universally) when it is used in its fullest sense, in which it is used in the sense of “each and every” of its kind or class. Thus in the proposition “Horses are animals” the meaning is that “_each and every_” horse is an animal–in this case the _subject_ is “distributed” or made universal. But the _predicate_ is _not_ “distributed” or made universal, but remains particular or restricted and implies merely “some.” For the proposition does not mean that the class “_horses_” includes _all_ animals. For we may say that: “_Some_ animals are _not_ horses.” So you see we have several instances in which the “distribution” varies, both as regards the subject and also the predicate. The rule of logic applying in this case is as follows:
1. In _universal_ propositions, the _subject_ is distributed.
2. In _particular_ propositions, the _subject_ is _not_ distributed.
3. In _negative_ propositions, the _predicate_ is distributed.
4. In _affirmative_ propositions, the _predicate_ is _not_ distributed.
A little time devoted to the analysis and understanding of the above rules will repay the student for his trouble, inasmuch as it will train his mind in the direction of logical distinction and judgment. The importance of these rules will appear later.