LOGIC.

CHAP. XXI.

IDEAS, WORDS, CLASSIFICATION, AND DEFINITION.

Object-Division-Sources of Ideas-Simple Ideas-Complex Ideas-Substance-Modes-Simple-Mixed-Ideas of Relation-Importance of the knowledge of Words-Sources of Names-Etymology-AmbiguityModes of conveying the Import of Words-Classification-Species-Genus-Arrangement of the Naturalist-Specific Difference-Comprehension-Extension - Predicables - Categories- Definition-Properties of a good Definition-Maxims respecting the Use of Words.

THE Art of Logic is a system of rules and observations, by which the understanding is directed in the ascertainment of truth, and the communication of it to others.

It is evident that the foundation of Logic must be laid in the principles of the human understanding; and the Theory of Logic must, therefore, comprehend the investigation of those principles. It is on this account that we thought it best to

defer the present division of our work, till we had laid before our readers an outline of Mental Philosophy. And, though we shall not presume upon a complete acquaintance with the chapters relating to that science, yet they certainly will find it of great advantage in the judicious study of Logic. If, however, they are disposed to invert the order here adopted, and begin with Logic, we hope they will find this division intelligible, without further attention to the foregoing than what our references may require.

Logic is sometimes represented as the art of reasoning: but reasoning is only one of the operations of the understanding; and, taking the logical acceptation of the term, it is not the most important.

A large proportion of the technical terms and distinctions of the Logician, are of very little value; and they would scarcely deserve attention, were they not occasionally referred to in the writings of those who have been familiarized with them in the schools. Our object will be, to introduce our readers to an acquaintance with such as may, in some way or other, be of real utility; and to aid them in acquiring those principles, which may assist them in the proper use of their intellectual powers.

Logic is commonly divided into four parts: (1.) Perception, comprehending all that respects our ideas, without reference to the operations of judgment and reasoning, by which they may in part have been formed: (2.) Judgment, which respects those decisions of the understanding, which arise from the comparison of the objects of thought: (3.) Reasoning, which includes those operations of the mind, by which the relation between two objects of thought is inferred from their mutual relation to an other: and (4.) Arrangement, or Method, which has for its object, the disposal and arrangement of our thoughts in that order which will best display their mutual connexion and dependence.

Some writers on Logic omit the last division; considering it as conveniently falling under the head of Reasoning. The

fact is, the operations of the understanding are so complex, and so intimately connected one with another, that it is not always easy to discriminate them. It is not, however, of great consequence to our present purpose, to enter into any nice discussion of these points; but to avoid communicating any erroneous ideas respecting the processes of the mind, we shall adopt a division less scientific in form, but which will better answer the leading object already stated. We shall, therefore, arrange this division under the following heads: Ideas, Words, Classification and Definition, Propositions, Evidence; Syllogisms and Sophisms, Observations on the Pursuit of

Truth.

IDEAS.

According to the views which we have already endeavoured to convey to our readers, our ideas (with the exception of those of reflection,) are the relics of sensation, variously combined by the operation of the associative power, and modified, in different ways, by the exercise of the understanding. And to avoid unnecessary repetition, we shall presume upon our readers here re-perusing what we have said (p. 246-248) on the distinctions of ideas as founded on the laws of association; and proceed to add a few observations respecting Mr. Locke's phraseology, which was framed before the operations of the associative power in the formation of ideas had been investigated, but which still is most commonly adopted by the writers on Logic.

1;

Mr. Locke supposes all our ideas to be derived either from sensation or from reflection; and that these are, with infinite variety, compounded and enlarged by the understanding. So far, apparently without any acquaintance with the compounding influence of association, that great philosopher had proceeded; and in this view he is undoubtedly borne out by all that is known of the operations of the mind.

The term simple idea, in Mr. Locke's nomenclature, is applied to all ideas which we cannot consider as made up of

parts. Such for instance are, (1.) the ideas of light and colours, sounds, tastes and smells, of heat and cold and solidity; (2.) those of extension, figure, rest, motion, &c. Some of these are derived from one sense alone; the second class from more than one sense.

Now a very slight acquaintance with the actual formation of our ideas, will convince any one, that the denomination simple idea must not be considered as referring to the ideas themselves, but to the qualities which are the objects of them, and from which they are derived. Our notion of solidity, for example, so far from being a simple idea, in the strict sense of the term, is derived from a vast number of impressions, producing the sensation which we experience when a solid body is applied to the sense of feeling. The notion of figure is still more complex, being derived not only from a number of sensations, but also from such as vary greatly from one another. The idea of a particular plain figure, may be a simple idea; but the notion connected with the word figure, is extremely complex. When, therefore, in Mr. Locke's language, we speak of simple ideas, we are not to understand the word simple as expressive of the simplicity of the ideas themselves, and implying that they are elementary ideas, (derived from single sensations through one sense ;) but as referring to the simplicity of the qualities of which they are the ideas. We cannot conceive or think of solidity as a divisible quality; and the idea of solidity may, therefore, be termed a simple idea.

In this application of the term, there may be simple ideas of reflection as well as of sensation; such as those connected with the words volition, feeling, recollection, &c. These operations or states of mind, are simple, and, therefore, the ideas of them may be called simple; though there is no doubt that each of these is formed from numerous impressions produced by attention to the corresponding states or oper

ations.

Following the same method of classification, Mr. Locke

calls those ideas complex, (without reference to their being composed of elementary simple ideas,) which are derived from objects capable of being represented to the mind as compounded of different parts or qualities. For example, the idea of an army he considers as complex, (not because the notion affixed to the term is derived from a variety of impressions in connexion with it, made either through direct observation, or by oral communication,) but because we can consider an army as made up of parts. He does, however, employ this term much more widely, to denote all ideas which are derived from any operation of the intellect, except the simple ones of sensation and reflection: and though it appears, from the theory of association, that he was sometimes mistaken as to the nature of complex ideas, yet his use of the term on the whole sufficiently corresponds with the Hartleyan acceptation of it.

The mind is in some sense passive, in the reception of simple ideas; its attention of course is requisite, but this is all. When the attention is given to the object from which they are derived, it cannot exclude or change them. They may be recalled by various associated ideas; but they cannot be communicated to any one who has not had the external or internal impressions by which they were produced. To endeavour to convey to a blind man a conception of colour, to a deaf man an idea of sound, or to a person who never reflected on what passes within him, an idea of the act of judging, would be perfectly useless.

Complex ideas may be conveyed, where the simple ideas composing them have been received. And it is the object of definition, or description, to produce in the mind of the hearer the notions or conceptions which are in the mind of the speaker.

Though the elementary ideas which enter into complex ideas, must have been derived from sensation or reflection, yet many of the combinations of them formed by the operations of the mind, have no archetype, or real existence correspond