is not essential to the operation in question. I may recollect or be told of a fact, and thus knowing it from recollection or testimony, I may form the same inferences from it as if I perceived it.

This determination of the mind to the belief of something beyond its actual perception or knowledge, is obviously what is termed reasoning.

There is, however, another mental operation to be noted, which consists, not in our being led to believe, or in our inferring from what we perceive and know, something else, neither perceived nor known; but in our being led to discern some fact, not directly manifest, through the medium of some other fact or facts in which it is implied.

Suppose somebody to assert that the opposite angles made by the intersection of two right lines are equal. This, at the first glance, appears likely enough to be true; but it is not intuitively perceived, it is not immediately A manifest. When, however, he proceeds to point out that the

angles ABD and ABC are together equal to two right angles, and that the angles A B D and DBE are also together equal to two right angles, we discern D

B

C

E

that these two pairs of angles are equal to each other; and when he further points out the circumstance of the angle A B D being common to the two equal pairs, we at once discern that the other angle

ABC of the first pair is equal to the other angle DBE of the second pair.

Here we do not infer the existence or the happening of something past, or future, or absent; but we are led to discern something not directly obvious, by an arrangement of propositions expressive of facts, each of which implies its successor.

To describe it more particularly:

The complex fact, or combination of facts, expressed in the proposition, "the two pairs of angles are respectively equal to two right angles," implies (or leads the mind to discern) that they are mutually equal; and the fact that the pairs, thus proved to be equal, have one angle in common, implies (or leads the mind to discern) that the remaining angle in the one is equal to the remaining angle in the other. Thus, if we regard the facts, there is self-evident involution or implication; and if we regard the mind of the reasoner, there is intuitive discernment at every step of the process.

The operation just described is termed reasoning equally with the other; but there is evidently an important difference between them. To be determined by facts to the belief of an unobserved event or object, past, present, or future, and to discern when two facts are presented to the mind, that one is implied in the other, are intellectual acts or operations plainly distinct. If there were no other circumstance by which to discriminate them, they would be broadly distinguished by this,

that in the latter species of reasoning, every step being discerned to be necessarily true, the denial of the conclusion involves a contradiction, while in the former species it does not. The conviction in the one case, and the discernment in the other, have, nevertheless, this in common, that the fact expressed in the conclusion is not in either case evident of itself, but is arrived at through the medium of some other fact or facts.

Of these two species of reasoning, while the second has been uniformly termed demonstrative, the first has sometimes been called moral, and sometimes probable reasoning; but on account of the ambiguity of these appellations, as will be explained in the next chapter, I shall venture to speak of it under the designation of contingent reasoning. Although objections may doubtless be brought against the epithet contingent, so applied, it appears to me, on mature consideration, to be less exceptionable and more convenient than any

other.

The facts which determine the mind to the belief, or lead it to the discernment of other facts not immediately manifest, are usually spoken of under the designation of evidence or proofs; and when expressed in propositions preceding a conclusion, under that of premises.

To reason, is to go through proofs or evidence for or against any alleged fact. Frequently the fact alleged or expressed in the conclusion is placed

before the mind first, and the proof is adduced to substantiate it; but it also frequently happens, in the course of reflection, that a fact, or combination of facts, leads the mind to the belief or to the discernment of a fact before unknown, which is then seen in its logical place as the conclusion.

7

CHAP. II.

CONTINGENT REASONING.

THE preceding chapter having shown that there are two distinct mental processes which pass under the name of reasoning, I purpose next to inquire more closely into the nature of the first of these processes, the principles on which it proceeds, and the foundation of its cogency.

SECTION I.

The Nature and Cogency of Contingent Reasoning.

Let us examine any simple instance of the first species of reasoning. The one already cited, respecting the sea-weed found on the beach, may serve the purpose. What takes place on such an occasion may be described as follows:

Having previously observed the tide, in ebbing, leave the sea-weed high upon the beach, as I see it at the present time, the recollection of this fact