Inference by Complex Conception

In one line

Inference by complex conception makes each of the two terms part of a larger conception, in the same way, and concludes that the relation still holds.

In the wording a student can write in an examination: an inference by complex conception is one in which the subject and the predicate of the given proposition are each made a constituent of a more complex notion, the same relation being applied to both, so that from "S is P" one infers "the R of S is the R of P".

The form

"A horse is an animal" gives "The head of a horse is the head of an animal."

"A partner is an agent of the firm" gives "The act of a partner is the act of an agent of the firm."

"A decree is an adjudication" gives "The execution of a decree is the execution of an adjudication."

The added element is a relation: head of, act of, execution of. It is applied to both terms, and nothing else changes.

How it differs from added determinants

The last chapter added a qualifying word to each term, and the terms stayed in view: a white horse is still a horse.

This chapter adds a relation, and the terms drop out of view: the head of a horse is not a horse. What is being asserted is that whatever stands in the relation R to an S also stands in the relation R to a P.

That is why the two topics are set together and why they fail in different ways. Added determinants fails when the qualifier means two different things. Complex conception fails when the relation does not transfer from the species to the genus.

When it holds

The inference is sound when the relation applies to the subject in virtue of what the subject and the predicate have in common.

A horse has a head because it is an animal, so the head of a horse is the head of an animal. A partner acts as an agent, so the act of a partner is the act of an agent. In each case the relation attaches to the wider class as readily as to the narrower one.

When it fails

One: the relation attaches to the narrower class only. "A rupee is money" does not give "the design on a rupee is the design on money", because money in general has no design; the design belongs to the coin and not to the class.

Two: the relation is not distributive over the class. "A judge is a person" does not give "a majority of the judges is a majority of the persons". Whatever "majority of" relates to, it relates to a determinate body, and the persons at large are not one.