act or object of the mind. But, as applied in Logic, they are strictly limited to one well-defined class of our cognitive functions. After the illustrations that have now been given, the peculiar characteristics of Thought properly so called are perhaps sufficiently understood.

Hamilton justly observes, that most of the words which signify operations of the mind have a triple ambiguity, for they may denote either, 1. the faculty; or, 2. the act; or, 3. the product of the act. To avoid this uncertainty, the Understanding is here used exclusively to denote the Faculty of Thinking in the narrower sense, or what Hamilton calls the "Elaborative Faculty," because it elaborates, or works up into Thought, the raw material which is furnished. to it by the Perceptive powers. Like any other faculty, the Understanding at any particular time may, or may not, be in exercise. Its function or peculiar office is to think ; hence, thinking denotes the act, while Thought signifies the product, of this faculty. As will be shown hereafter, Thought is the generic term, for there are three species of it; viz. Concepts, Judgments, and Reasonings or InferThe old logicians referred the origin of these three species of Thought to as many distinct faculties, which they denominated respectively Simple Apprehension, Judgment, and the Discursive Faculty. Of these, Simple Apprehension corresponds very nearly to that sort of Thinking which we now call Conception, its products being denominated Concepts. In like manner, the products of the Perceptive or Acquisitive Faculty, hitherto called Intuitions, might more conveniently be termed Percepts, as we should then have an English verb, perceive, to express the act of that Faculty of which these are products. If it were allowable to coin an English verb to express the act of intuition, answering to the German anschauen, analogy would direct us to say intuit. The Discursive Faculty (from discurrere, to run to and fro) was so called because, in Reasoning or

ences.

drawing Inferences, the mind runs over from one Judgment, as the Ground or Reason, to another, as the Consequence or Conclusion. But the whole Understanding is more properly called by this name; for, in forming Concepts, the mind runs over the Percepts or Intuitions from which they are derived, in order to separate the similar elements from the unlike, and consciously to unite the former into one product of Thought.

L

CHAPTER II.

DEFINITION OF LOGIC.

Divisions of the Science. - Utility of the Study.

OGIC is the Science of the Necessary Laws of Pure
Thought.

The Greek word, λóyos, from which Logic is derived, signifies both the inward thought, and the word or outward form in which this thought is expressed; and thus includes both the ratio and the oratio of the Latins. This fact, and the intimate connection which, as we have already seen, exists between Thought and Language, has caused some writers, especially those who adopt the Nominalist theory to its full extent, to maintain that "Logic is entirely conversant about Language.' But it is not so; for Logic is primarily and essentially conversant with Thought, and only secondarily and accidentally with Language; that is, it treats of Language so far only as this is the vehicle of Thought. Just the reverse is true of the science of Grammar, which treats primarily of Language, and only secondarily of Thought. Logic might be called the Grammar of Thought.

Others have held that "the process or operation of reasoning is alone the appropriate province of Logic." But this is putting the part for the whole, and is as inadequate as it would be to restrict Geometry to the measurement of spherical bodies, to the exclusion of lines, angles, plane surfaces, and rectilinear solids. There are three classes of the products of Thought, namely, Concepts, Judgments, and

ers.

Inferences or Reasonings, with each of which Logic is immediately concerned, as, indeed, no one of them can be adequately discussed without consideration of both the othIf, on the one hand, it can be said that conception and judgment are both subsidiary to the process of reasoning, so, on the other, judgment is the primary and essential operation, of which conception and inference are only special forms or complex results.

Pure, or, as it is sometimes termed, Formal Thought, is the mere process of thinking, irrespective of what we are thinking about. It has already been said that the Acquisitive or Perceptive Faculty furnishes "the Matter," while the Understanding supplies "the Form," of our knowledge. This distinction between Matter and Form is one of considerable importance in the history of philosophy. The former is the crude material or the stuff of which anything consists, or out of which it is made; while the latter is the peculiar shape or modification given to it by the artist, whereby it has become this particular thing which it is, and not something else which might have been fashioned out of the same substance. Thus, wood is the Matter of the desk on which I am writing, whilst the Form is that which entitles it to be called a desk, rather than a table or a chair. Vocal sound is the Matter of speech, and articulation is its Form. It is evident that these are two correlative notions, each of which implies the other: Matter cannot exist except under some Form, and there cannot be any Form except of some given Matter. But though the two cannot actually be separated, the mind can consider each separately through that process, called abstraction, whereby the attention is wholly given to the one to the exclusion of the other. We may think separately of the attributes which are common to a whole class of Forms, disregarding altogether, for the moment, the Matter of which each of them really consists. Borrowing algebraic symbols, the Matter in each

case may be designated by a letter of the alphabet, the peculiar significance of which is, that it stands for any Matter whatever, and not for any one in particular. Thus, A is B, is the Form of an affirmative judgment, wherein A and B stand for any two Concepts whatever. Hence, whatever is true of the general formula, A is B, will be true also of any such particular instances, as Iron is malleable, Trees are plants, &c., wherein the Form is associated with some particular Matter. In saying, then, that Logic is concerned only with the Forms of Thought, or Pure Thought, or Thought in the abstract,- for all these expressions signify the same thing, - we mean only, that what is Material in Thought is extralogical, and, as logicians, we have nothing to do with it; just as the geometer has nothing to do with the particular diagram on the paper before him, except so far as it is a symbol, or universal Form, of all possible figures of the same general character. As Hamilton remarks: "The objects (the Matter) of thought are infinite; no one science can embrace them all, and therefore to suppose Logic conversant about the Matter of thought in general, is to say that Logic is another name for the encyclopædia the omne scibile-of human knowledge. The absurdity of this supposition is apparent. But if it be impossible for Logic to treat of all the objects of thought, it cannot be supposed that it treats of any; for no reason can be given why it should limit its consideration to some, to the exclusion of others. As Logic cannot, therefore, possibly include all objects, and as it cannot possibly be shown why it should include only some, it follows that it must exclude from its domain the consideration of the Matter of thought altogether; and as, apart from the Matter of thought, there only remains the Form, it follows that Logic, as a special science of thought, must be viewed as conversant exclusively about the Form of thought."

Again, the definition of Logic assumes that the process