Corol. The term impression, consequently, in the department of logic and mental science, merely denotes whatever produces that change in the mind which is necessary to perceive an object, or to form a thought.

39. Sensation is a name given by philosophers to an act of mind, which may be distinguished from all others by this, that it hath no object distinct from the object itself.

Illus. Pain of every kind is an uneasy sensation. When I am pained, I cannot say, that the pain I feel is one thing, and that my feeling it is another thing. They are one and the same thing, and cannot be disjoined even in imagination. Pain, when it is not felt, has no existence. It can be neither greater nor less in degree, or duration, nor any thing else in kind, than it is felt to be. It cannot exist by itself, nor in any subject, but in a sentient being. No quality of any inanimate and insentient being can have the least resemblance to it.

40. What we have said of pain may be applied to every other sensation; some of them are agreeable, others uneasy, in various degrees.

Obs. These being objects of desire or aversion, have some attention given to them; but many are indifferent, and so little attended to, that they have no name in any language.

41. Most operations of the mind, that have names in common language, are complex in their nature, and made up of various ingredients, or more simple acts; which, though conjoined in our constitutions, must be disjoined by abstraction, in order to our having a distinct and scientific notion of the complex operation. In such operations, sensation, for the most part, makes an ingredient. Those who do not attend to the complex nature of such operations, are apt to resolve them into some one of the simple acts of which they are compounded, overlooking others.

Obs. Nothing, therefore, is of so much importance as to have a distinct notion of that simple act of the mind which we call sensation, without puzzling ourselves about the particular nature of the change effected in the organ, in the nerves, or in the brain, by the secondary qualities of matter, in the process which constitutes sensation, and of which we can have no clearer knowledge than if we ourselves were not the subjects of that mysterious operation.

42. The word feeling hath two meanings.

First, It signifies the perceptions which we have of external objects, by the sense of touch. When we speak of feeling a body to be hard or soft, rough or smooth, hot or cold; to feel these things, is to perceive them by touch.

Secondly, The word feeling is used to signify the same thing as sensation, which we have just explained; and in

1

this sense, it has no object; the feeling and the thing felt, are one and the same.

Obs. Perhaps betwixt feeling, taken in this last sense, and sensation, there may be this small difference, that sensation is most commonly used to signify those feelings which we have by our external senses and bodily appetites, and all our bodily pains and pleasures. But there are feelings of a nobler nature accompanying our affections, our moral judgments, and our determinations in matters of taste, to which the word sensation is less properly applied. Note. Other words that need explication, shall be explained as they occur.

CHAPTER II.

PRINCIPLES TAKEN FOR GRANTED.

43. A GENERAL rule, when applied to regulate particulars, is termed a principle; and explanations or injunctions from principle are termed theory, or system. The particulars to be explained are termed phenomena.

Obs. As there are words common to philosophers and to the unlearned, which need no explication; so there are principles common to both which need no proof, and which do not admit of direct proof.

44. Such principles, when we have occasion to use them in science, are called axioms.

Illus. Thus, mathematicians, before they attempt to prove any proposition in mathematics, lay down certain axioms or common principles, upon which they build their reasonings. And although those axioms be truths which every man knew before; such as, "That the whole is greater than a part"-" that equal quantities added to equal quantities make equal sums;" yet, when we see nothing assumed in the proof of mathematical propositions, but such self-evident axioms, the propositions appear more certain, and leave no room for doubt or dispute.

45. In every other science, as well as in mathematics, it will be found that there are a few common principles, upon which all the reasonings in that science are grounded, and into which they may be resolved. If these principles were pointed out and explained, we should be better able to judge what stress may be laid upon the conclusions in that science. If the principles be certain, the conclusions justly drawn from them must be certain. If the principles be only probable, the conclusions can only be probable. If the princi

ples be false, dubious, or obscure, the superstructure that is built upon them must partake of the weakness of the foundation.

Illus. Thus, Sir Isaac Newton, by laying down the common principles or axioms, on which the reasonings in natural philosophy are built, laid a solid foundation in that science, and reared on it a noble superstructure, about which there is no more dispute or controversy among men of knowledge, than there is about the conclusions of mathematics. Yet are the first principles of natural philosophy of a nature quite different from mathematical axioms. They have not the same kind of evidence, nor are they necessary truths, as mathematical axioms are. They are such as these, "that similar effects proceed from the same or similar causes; that we ought to admit of no other causes of natural effects, but such as are true, and sufficient to account for the effects." These are principles, which, though they have not the same kind of evidence that mathematical axioms have; yet have such evidence, that every man of common understanding readily assents to them, and finds it absolutely necessary to conduct his actions and opinions by them, in the ordinary affairs of life.

46. In like manner, there are some things which we shall take for granted, as first principles in treating of the mind and its faculties; or of a rational and useful logic.

47. The evidence of first principles is not demonstrative but intuitive. They require not proof, but to be placed in a proper point of view.

48. First, then, we shall take it for granted, that man thinks, remembers, reasons, and, in general, that he really performs all those operations of mind, of which he is conscious.

Illus. The operations of our minds are attended with consciousness; and this consciousness is the evidence, the only evidence which we have, or can have, of their existence. Every man finds himself under a necessity of believing what consciousness testifies, and every thing that hath this testimony is to be taken as a first principle.

49. As by consciousness we know certainly the existence of our present thoughts and passions; so we know the past by remembrance. And when they are recent, and the remembrance of them fresh, the knowledge of them, from such distinct remembrance, is, in its certainty and evidence, next to that of consciousness.

50. When we make our own thoughts and passions, and the various operations of our minds the objects of our attention, either while they are present, or when they are recent and fresh in our memory, this act of the mind is called reflection.

Corol. We take it for granted, therefore, that by attentive reflection, a man may have a clear and certain knowedge of the operations of his own mind; a knowledge no less clear and certain, than that which he has of an external object when it is set before his eyes.

51. This reflection is a kind of intuition, it gives a like conviction with regard to internal objects, or things in the mind, as the faculty of seeing gives with regard to the objects of sight.

Corol. A man must, therefore, be convinced beyond the possibility of doubt, of every thing with regard to the operations of his own mind, which he clearly and distinctly discerns by attentive reflection.

52. We shall take it for granted, that all the thoughts which a man is conscious of, or remembers, are the thoughts of one and the same thinking principle, which he calls himself, or his mind.

Illus. 1. Every man has an immediate and irresistible conviction, not only of his present existence, but of his continued existence and identity as far back as he can remember.

2. Every man of a sound mind feels himself under a necessity of believing his own identity, and continued existence. The conviction of this is immediate and irresistible; and if he should lose this conviction, it would be a certain proof of insanity, which is not to be remedied by reasoning.

53. We shall take it for granted, that there are some things which cannot exist by themselves, but must be in something else to which they belong, as qualities, or attri

butes.

Illus. Thus, motion cannot exist but in something that is moved. For, to suppose that there can be motion while every thing is at rest, is a gross and palpable absurdity. In like manner, hardness and softness, sweetness and bitterness, are things which cannot exist by themselves. They are qualities of some thing which is hard or soft, sweet or bitter. That thing, whatever it be, of which they are qualities, is called their subject, and such qualities necessarily sup pose a subject.

54. Things which may exist by themselves, and which do not suppose the existence of any thing else, are called substances; and with relation to the qualities or attributes that belong to them, they are called the subjects of such qualities or attributes. And, in respect to material objects, we give the name of body to that which is the subject of these qualities or attributes.

55. In like manner, those operations of which a man is conscious, such as thought, reasoning, desire, necessarily suppose something that thinks, reasons, and desires. do not give the name of mind to thought, reason, or desire;

We

but to that being which thinks, which reasons, and which desires.

56. That every act, or operation, therefore, supposes an agent, that every quality supposes a subject, are things which we do not attempt to prove, but take for granted. Every man of common understanding discerns this immediately, and cannot entertain the least doubt of it.

57. In all languages, we find certain words which, by grammarians, are called adjectives. Such words denote attributes; and every adjective must have a substantive to which it belongs, because every attribute must have a subject.

58. In all languages, we find active verbs, which denote some action or operation: and it is a fundamental rule in the grammar of all languages, that such a verb supposes a person, that is, in other words, every action must have an agent.

Corol. We take it, therefore, as a first principle, that goodness, wisdom, and virtue, can only be in some being that is good, wise, and virtuous; that thinking supposes a being that thinks, and that every operation of which we are conscious supposes an agent that operates, which we call mind.

59. We take it for granted, that in most operations of the mind, there must be an object distinct from the operation itself.

Illus. 1. I cannot see, without seeing something. To see without having an object of sight is absurd. I cannot remember, without remembering something. The thing remembered is past, while the remembrance of it is present; and therefore the operation and the object of it must be distinct things.

2. I remember the comet of 1811. Here the act of remembering is present, but the comet, which is the object of this act, is absent; whence the operation and the object of that operation are distinct things.

60. We ought likewise to take for granted, as first principles, things wherein we find an universal agreement among the learned and unlearned, in the different ages of the world.

Obs. A consent of ages and nations, of the learned and unlearned, ought, at least, to have great authority, unless we can shew some prejudice, as universal as that consent is, which might be its cause. Truth is one, but error is infinite.

Corol. An universal consent in things gives the greatest presumption that can be, that such a consent is the natural result of the human faculties, and must have great authority with every sober mind that loves truth.