The Scottish Philosophy [288]
discover this truth." "If it should farther be inquired how far the truth of self-evident propositions depends on the constitution of the being that perceives them, the answer to this question is no less easy and obvious. As every truth expresses some attribute of a thing, or some relation between two or more things, the truth depends on the nature of the thing whose attribute is expressed. The truth of this proposition, that a lion is a ravenous beast, depends upon the constitution of a lion, and upon nothing else. The truth of this proposition, that the sun is greater than the moon, depends upon the magnitude of the sun and moon, and upon nothing else." In like manner as to right and wrong. " Although the rectitude or depravity has a real existence in the agent in this case, yet it cannot be discerned by a spectator who has not the faculty of discerning objects of this kind." " Why do I believe first principles?" "One philosopher says, Because I am so constituted that I must believe them. This, say some, is the only possible reason that can be given for the belief of first principles. But, say others, this is a very bad reason; it makes truth a vague thing which depends on constitution. Is not this the ancient sceptical system of Heraclitus, that man is the measure of truth, that what is true to one man may be false to another? How shall we judge of this controversy? Answer, This question admits of two meanings. 1. For what reason do you believe first principles? 2. To what cause is your belief of first principles to be ascribed?" "To first, evidence is the sole and ultimate ground of belief, and self-evidence is the strongest possible ground of belief, and he who desires a reason for believing what is self-evident knows not what he means." To the second the answer is not so satisfactory. It is "that belief is a simple and original operation of the mind which always accompanies a thing we call evidence." "If it should be asked, what this evidence is which so imperiously commands belief, I confess I cannot define it." "If it should farther be asked, what is the cause of our perceiving evidence in first principles, to this I can give no other answer but that God has given us the faculty of judgment or common sense.' The paper closes thus: "Q. Is there not a difference between the evidence of some first principles and others? A. There are various differences perhaps. This seems to be one, that, in some first principles, the predicate of the proposition is evidently contained in the subject: it is in this, two and three are equal to five; a man has flesh and blood. In these and the like self-evident principles, the subject includes the predicate in the very notion of it. There are other first principles in which the predicate is not contained in the notion of the subject; as, where we affirm that a-thing which begins to exist must have a cause. Here the beginning of existence and causation are really different notions, nor does the first include the last. Again, when I affirm that the body which I see and feel really exists, existence is not included in the notion of a body. I can have the {476}notion of it as distinct when it is annihilate. The truth of principles of the first kind is only perceiving some part of the definition of a thing to belong to it, and such propositions are indeed of very little use: they may justly, as Mr. Locke observes, be called trifling propositions. One general maxim may include all first principles of this kind; viz., Whatever is contained in the definition of a thing may be predicated of it. But in reality the definition sufficiently supplies the place of such axioms. That the sides of a square are equal, that all the radii of a circle are equal, these do not deserve the name of axioms; for they are included in the definitions of a square and of a circle. Of the same kind are these propositions that an effect must have a cause, that a son must have a father. There is nothing affirmed in such propositions but what is contained in the definition or in the notion of the terms. There are other