Correlative Terms

Correlative terms are also called relative or reciprocal terms, and may be considered as opposite terms. Mother and child are correlative terms, that is, they are linked by the immediate inference:

if A is the mother of B, then B is the child of A

Correlative terms are defined by reference to one another; mother is defined as “woman with children”; child as “son or daughter of M”.
The following terms are correlatives:

cause / effect                  double / half                  master /slave
action / passion              sell / buy

Generally speaking, two predicates R1 and R2 are in a correlation relation when

A_R1_B <=> B_R2_A
A_mother_B <=> B_child_A

 “By definition, correlatives are opposites”; they are “ontologically simultaneous” (Hamelin [1905], p. 133). The topic of the correlative is n°3 on Aristotle’s list:

Another line of proof is based upon correlative ideas (Rhet, II, 23, 3; RR, p. 357)

The topic is exemplified by the enthymemes:

Where it is right to command obedience, it must have been right to obey the command.

 The tax-farmer: ”if it is no disgrace for you to sell it, it is no disgrace for us to buy it” (ibid.).

These inferences have limitations:

If it is legal/tolerated to buy 2 g of marijuana, then one may sell 2 g of marijuana.

But what about “possessing” and “buying”?

if it is legal/tolerated to possess 2g of marijuana,
then it is legal/tolerated to buy 2 g,
then it is legal/tolerated to sell it

given that for me, the only way to get marijuana is to buy it. But the law can make a distinction between two kinds of “possession”: the possession of drugs for private consumption is not an offence, while possession for trafficking is.

The following case deals with two pairs of correlatives, know / learn, and order / obey, articulated by the topic of the opposites:

If you want to command, you must first learn to obey.
The executive, when he was on his way up, had to learn to obey so that he should know how to command (quoted in Linguee).