Logic is the art of forming correct ideas, and of de ducing right inferences from them; or it may be said to constitute the knowledge of the human mind, inasmuch as it traces the progress of all our information, from our first and most simple conceptions of things, to those numerous conclusions, which result from comparing them together. It teaches us in what order our thoughts succeed each other, and it instructs us in the relation which subsists between our ideas, and the terms in which we express them. It distinguishes their different kinds, and points out their properties; discovers the sources of our intellectual mistakes, and shows how we may correct and prevent them. It displays those principles and rules, which we follow, although imperceptibly, whenever we think in a manner conformable to truth.

The faculty of reason is the preeminent quality, by which mankind are distinguished from all other animals but still we are far from finding that they possess it in the same degree. There is indeed as great an inequality in this respect in different persons, as there is in their strength and agility of body. Nor ought this disproportion to be wholly ascribed to the original constitution of the minds of men, or the difference of their natural endowments; for, if we take a survey of the nations of the world, we shall that find some are immersed in ignorance and barbarity, others enlightened by learning and science: and what is still more remarkable, the people of the same nation have been in various ages distinguished by these very opposite characters. It is therefore by due cultivation, and proper diligence, that we increase the vigour of our minds, and carry reason to perfection. Where this method is followed, the intellect acquires strength, and know

ledge is enlarged in every direction; where it is neglected, we remain ignorant of the value of our own powers; and those faculties, by which we are qualified to survey the vast fabric of the world, to contemplate the whole face of nature, to investigate the causes of things, and to arrive at the most important conclusions as to our welfare and happiness, remain buried in darkness and obscurity. No branch of science therefore affords us a fairer prospect of improvement, than that which relates to the understanding, defines its powers, and shows the method, by which it acquires the stock of its ideas, and accumulates general knowledge :this is the province of logic.

It is properly divided into four parts, viz.

I. PERCEPTION. II. JUDGMENT.

III. REASON

In this division the logicians have followed the course of nature, as we shall find, if we reflect upon the conduct and progress of the understanding. These divisions have so close a connexion with each other, that it is scarcely possible to arrive at perfection in one of them, without the assistance of the others. To treat of perception we must make use of method; and in order to reason we must form every proposition with a due regard to rules.

I. PERCEPTION consists in the attention of the understanding to the objects acting upon it, whereby it becomes sensible of the impressions they make; and the notices of these impressions, as they exist in the mind, are distinguished by the name of ideas. If we attend carefully to our thoughts, we shall observe two fountains or sources of knowledge, from which the understanding is supplied with all its ideas, or

materials of thinking. These are sensation and reflection.

Sensation is the source of our original ideas, and comprehends the notices conveyed into the mind by impulses or impressions made upon the organs of sense. Such are the perceptions of colours, sounds, tastes, &c. But we derive all these ideas, great as is their number, solely from external objects. Another source of impressions arises from the attention of the mind to its own perceptions, and considers the various modes, in which it employs itself concerning them. Thus we acquire the ideas of thinking, doubting, believing, &c. which are the different intellectual operations represented to us by our own consciousness. This act of the mind is called reflection; and it evidently implies sensation, as the impressions it furnishes proceed from the powers of the understanding occu pied in the contemplation of ideas, with which it has been previously stored.

A proper consideration of these two sources of our thoughts will give us a clear and distinct view of the nature of the mind, and the first steps it takes in the path of knowledge. From these simple beginnings all our discoveries derive their origin; for the mind thus stored with its original notices of things has a power of combining, modifying, and placing them in an infinite variety of lights, by which means it is enabled to multiply the objects of its perception, and finds itself possessed of an inexhaustible stock of materials for reflection and reasoning. It is in the various comparisons of these ideas, according to such combinations as are best adapted to its ends, that wẻ exert ourselves in the acts of judging and reasoning, enlarge our mental prospects, and can extend them in

every direction. Thus are we enabled to form a notion of the whole progress of the soul, from the first dawnings of thought to the utmost limits of human knowledge. And it is particularly to be observed, that among our numerous discoveries, and the infinite variety of our conceptions, we are unable to find one original idea, which is not derived from sensation or reflection; or one complex idea, which is not com. posed of these original ones. "Our observation employed either about external sensible objects, or about the internal operations of our minds, perceived and reflected on by ourselves, is that which supplies our understandings with all the materials of thinking. These two are the fountains of knowledge, from whence all the ideas we have, or can naturally have, do spring." Locke, book ii, chap. 1. see likewise book i, chap. 2. and book ii, chap. 1.

The ideas, with which the mind is thus furnished, fall naturally under two heads. First, those original impressions which are conveyed by sensation and reflection, and which exist uniformly and without any shadow of variety, and are called simple ideas, such as the ideas of colour, sound, heat, &c. And, secondly, those notions which result from the various combinations of simple ideas, whether they are supposed to co-exist in any particular subject, or are united together by the mind when it enlarges its conceptions. These are called complex ideas, such as a triangle, a square, &c. and are of two principal kinds; first, such as are derived from external objects, and represent those combinations of thought, which have a real existence in nature; of this kind are all our ideas of substances. Secondly, the conceptions formed by the mind itself, arbitrarily uniting and putting together its ideas. This

makes by far the largest class, and comprehends all those ideas, which may be properly termed our own. They are called abstract or universal, such as whiteness, beauty, melody, &c. and are produced in various ways; for either the mind combines several simple ideas together, in order to form them into one conception, in which the number and quality of the ideas united are principally considered, and thus we acquire all our compound notions; or it fixes upon any of our ideas whether simple or compound; or upon the ideas of substances, and omitting the circumstances of time, place, real existence, or whatever renders it particular, considers the appearance alone, and makes that a representation of all that are of the same kind; or, lastly, it compares things with one another, examines their mutual connexions, and thereby furnishes itself with a new stock of notions, known by the name of relations, which are proportional, as equal, more, less, &c. or natural, as father, mother, &c. or civil, as king and people, general and army, &c. This division of our ideas, as it seems to be the most natural, and truly to represent the manner in which they are introduced into the mind, will be found to include them in all their varieties.

We know that our thoughts, although so numerous and manifold, are all contained within our own breasts, and are invisible. But as the Supreme Being formed mankind for society, he has provided us with organs proper for framing articulate sounds, and given us also a capacity of using those sounds, as signs of internal conceptions. From hence are derived words and languages. See Locke on the Ends of Language, book iii, c. 10. For any sound being once determined upon to stand as the sign of an idea, custom by degrees