Inference by Converse Relation

Where it goes wrong

One: naming the converse too narrowly. "A is the brother of B" does not give "B is the brother of A", because B may be a sister. The correct converse is "B is the sibling of A", or "B is the brother or sister of A". Over-specifying the converse is the commonest error in this topic and it is an easy mark to lose.

Two: symmetrical relations. Some relations are their own converses: "is married to", "is a partner with", "is contiguous with", "is a party to the same suit as". Here the inference is trivially available and there is nothing to name, but a student who invents a different word for the converse has gone wrong.

Three: relations that are not converses at all. "A is the employer of B" gives "B is the employee of A", and that is a converse. "A is the employer of B" does not give "B is the servant of A" without more, because "servant" is a legal characterisation with consequences, not simply the other end of a relation. Do not use the inference to smuggle in a legal conclusion.

Four: relations with more than two ends. "A paid B on behalf of C" has three terms, and there is no single converse. Several propositions can be drawn from it, "B received payment from A", "C's obligation was discharged by A", and each has to be derived on its own footing.

A worked example

A plaint alleges: "The defendant mortgaged the suit property to the plaintiff on 4 April 2022 to secure a loan of Rs 5,00,000."

Read off the converse relations. The defendant is the mortgagor; the plaintiff is the mortgagee. The defendant is the borrower; the plaintiff is the lender. The property is the security; the plaintiff is the person for whose benefit it is held.

What follows without further evidence. Every one of those propositions, because each is simply the same fact stated from the other end. A written statement that admits the mortgage and denies that the plaintiff is a mortgagee has admitted and denied the same thing, and the contradiction can be pointed out without a witness. That is the law of contradiction at sequence 160 applied through this chapter.

Now a trap. Suppose the plaint further alleges that "the plaintiff is entitled to possession". Does that follow by converse relation from the mortgage? No. Whether a mortgagee is entitled to possession depends on the kind of mortgage, and it is a legal consequence and not the other end of a relation. Attempting to reach it by this inference is error three above: smuggling a legal conclusion into a converse.

And a naming trap. If the plaint alleged that the defendant is "a relative of the plaintiff", the converse is "the plaintiff is a relative of the defendant", which is symmetrical and adds nothing. It does not give any more specific relation, and a pleading that reads a specific relationship out of a general one has over-specified the converse.

Distinctions that carry marks

What this does not mean

The converse relation is not the same relation. Creditor and debtor are two relations, not one used twice.

It is not conversion. Nothing is being done to a subject and a predicate, and the distribution rule has no application.

It does not establish legal consequences. It restates a fact from the other end, and what the law attaches to that fact is a separate question.

Quick revision

Form: from "A stands in relation R to B" infer "B stands in the converse relation to A".

Not conversion: the terms are arguments of a relation, not subject and predicate, and the relation itself changes.

The traditional scheme cannot represent relations, so this inference sits awkwardly in it, which is a fair point to make.

Legal pairs: creditor and debtor, mortgagor and mortgagee, lessor and lessee, bailor and bailee, principal and agent, assignor and assignee, plaintiff and defendant, appellant and respondent.

Practical value: proving one half proves the other, from a single piece of evidence.

Four errors: naming the converse too narrowly; inventing a converse for a symmetrical relation; smuggling in a legal conclusion; relations with more than two terms.

Test yourself

1. Define inference by converse relation and give an example.

It is the immediate inference from a proposition asserting a relation between two terms to the proposition asserting the converse relation between the same terms in reverse order. From "Ravi is the creditor of Bharat" it follows that "Bharat is the debtor of Ravi". The relation in the conclusion is not the same relation but its converse, running the other way between the same two things.

2. How does it differ from conversion?

Conversion interchanges the subject and the predicate of a categorical proposition, keeping the relation, which is the copula, and it is restricted by the distribution rule. Inference by converse relation operates on a relational proposition, keeping the two terms as the arguments of the relation and replacing the relation itself by its converse. The distribution rule has no application to it, and traditional logic could not represent it at all, since it had no way of writing a relation with two ends.

3. Give five pairs of converse relations from private law.

Creditor and debtor; mortgagor and mortgagee; lessor and lessee; bailor and bailee; principal and agent. Others include vendor and purchaser, assignor and assignee, trustee and beneficiary, and, in procedure, plaintiff and defendant and appellant and respondent. The whole vocabulary of obligations is built out of such pairs, which is why the inference is used constantly without being noticed.

4. What is the commonest error in naming a converse?

Naming it too narrowly. "A is the brother of B" does not give "B is the brother of A", since B may be a sister; the converse is "B is the sibling of A". The rule is to state the converse in the widest form the original supports, and any narrowing has to be justified by further facts rather than read out of the relation.

5. Why can this inference not establish a legal consequence?

Because it restates a single fact from the other end and adds nothing. That A is the mortgagor makes the plaintiff the mortgagee, which is the same fact seen the other way; whether the mortgagee is entitled to possession depends on the kind of mortgage and on the law, which the relation says nothing about. Using the inference to reach a legal characterisation is smuggling a conclusion into a restatement.

6. What happens where a relation has more than two terms?

There is no single converse. "A paid B on behalf of C" relates three parties, and several propositions can be drawn from it, such as that B received payment from A and that C's obligation was discharged by A. Each has to be derived on its own footing, and none of them is the converse of the original in the sense this inference uses, since a converse presupposes exactly two terms.