The maxim, that every effect must have a cause, is a self-evident and universal proposition. Its truth is involved in the very definition of the terms of which it is composed. In this respect it is like the axioms of geometry. When it is said, for example, that "the whole is equal to the sum of the parts," we at once perceive the truth of the axiom; because the "whole" is merely another name for "the sum of the parts." It is intuitively certain that they are equal, because they are but different expressions of the same thing. So, likewise, when it is affirmed, that every effect or every change in nature has a cause, we instantly perceive the truth of the proposition; inasmuch as an effect is that which is produced by a cause. The very idea of an effect implies its relation to a cause; and to say, that it has one, is only to say, that an effect is an effect. For if it were not produced by a cause, it would not be an effect. The maxim under consideration is as unquestionably true as any axiom in Euclid. It does not depend for the evidence of its truth upon observation, or experience, or reasoning; it carries its own evidence along with it. No sooner are the terms in which it is expressed understood, than it rivets irresistible conviction on the mind. It is a fundamental law of belief; and it is impossible for the imagination of man to conceive, that an effect, or that which is produced by a cause, should be without a cause. And it were just as idle an employment of one's time, to undertake to prove such a proposition, as it would be to attempt to refute it. Now, one of the fallacies of the argument of the necessitarian is, that it is an attempt to draw a conclusion from the axiomatical truth above referred to, as from the major of a syllogism. Every such attempt must necessarily be vain and fruitless. "Axioms," justly remarks Mr. Locke, "are not the foundations on which any of the sciences are built." And again, "It was not the influence of those maxims which are taken for principles in mathematics, that hath led the masters of that science into the wonderful discoveries they have made. Let a man of good parts know all the maxims generally made use of in mathematics never so perfectly, and contemplate their extent and consequences as much as he pleases, he will, by their assistance, I suppose, scarce ever come to know, that the square of the hypothenuse in a right-angled triangle, is equal to the squares of the two other sides. The knowledge, that the whole is equal to the parts, and, if you take equals from equals, the remainder will be equal, helped him not, I presume, to this demonstration. And a man may, I think, pore long enough on those axioms, without ever seeing one jot the more of mathematical truths."