Analogy. This term does not mean the resemblance of things but of ratios. The things may have no likeness to each other. When we say that as the brain is to the human body, so is the government to the body politic, we never suppose resemblance between a tissue in the skull, and the members of a government, or between the human frame and the organized population of a state, but we do assert resemblance in the relations which respectively subsist between them.

It is important to keep this distinction in mind, for otherwise we may fancy ourselves arguing from analogy when our reasoning is altogether futile. To infer that because two things are to each other as two other things are to each other, therefore these things are like or correspond in other particulars than those connected with this common ratio, is to infer without grounds. In order that what seems reasoning from analogy may be really such, the inference should be drawn from the ratio, and from nothing besides. In this case it will be, like all reasoning whatsoever, a syllogism, having for major that the results of a ratio may be expected in every case where such ratio subsists. In mathematics and arithmetic this syllogism leads of course to a necessary conclusion. In other matters it affords a probable one, but frequently so probable as to produce reasonable conviction.

The difference between real and seeming argument from analogy comes out very distinctly in men’s applications of that which subsists between an individual man and a nation. These of course are many and various. One well known is to the effect that as in each man there is, after growth and the adult condition have had their turn, a law of decrepitude and decay which finally produces dissolution, we are to expect the like in a nation, and however great and noble it may at one time have been, it must in the course of ages succumb to an old age of feebleness, if it do not die and perish altogether.

It is important to keep this distinction in mind, for otherwise we may fancy ourselves arguing from analogy when our reasoning is altogether futile. To infer that because two things are to each other as two other things are to each other, therefore these things are like or correspond in other particulars than those connected with this common ratio, is to infer without grounds. In order that what seems reasoning from analogy may be really such, the inference should be drawn from the ratio, and from nothing besides. In this case it will be, like all reasoning whatsoever, a syllogism, having for major that the results of a ratio may be expected in every case where such ratio subsists. In mathematics and arithmetic this syllogism leads of course to a necessary conclusion. In other matters it affords a probable one, but frequently so probable as to produce reasonable conviction.

The difference between real and seeming argument from analogy comes out very distinctly in men’s applications of that which subsists between an individual man and a nation. These of course are many and various. One well known is to the effect that as in each man there is, after growth and the adult condition have had their turn, a law of decrepitude and decay which finally produces dissolution, we are to expect the like in a nation, and however great and noble it may at one time have been, it must in the course of ages succumb to an old age of feebleness, if it do not die and perish altogether.

Analysys

Analysis. See Method.