Inference and Its Kinds: Immediate and Mediate

Inference by opposition, topic 3.2. From the truth or falsity of one of A, E, I and O, what follows about the other three. Sequences 410 to 430.

Eduction, topic 3.3. Transforming a proposition by changing the position or the quality of its terms: conversion, obversion, the obverted converse, contraposition and inversion. Sequences 440 to 490.

The other immediate inferences, topic 3.4. Material obversion, added determinants, complex conception and converse relation. Sequences 500 to 530.

A useful distinction between the first two. Opposition compares two different propositions with the same terms and asks how their truth values are related. Eduction transforms one proposition into another and asks whether the new one is entailed. The first is a relation, the second an operation.

Why immediate inference is worth learning

Because it is what a lawyer does with a provision before doing anything else.

A section says: "No suit shall be entertained unless notice has been given." What else follows from that sentence alone, without any facts and without any other provision? That every suit entertained is one in which notice was given. That some suits in which notice was given may still not be entertained, for other reasons. That the section says nothing whatever about suits in which notice was given.

Every one of those is an immediate inference, and each is a real conclusion about the section that can be stated before a single fact is known. Getting them wrong is how a provision comes to be read as saying the opposite of what it says, and sequence 310's worked example showed exactly that happening.

A worked example

Take the proposition: "No agreement without consideration is enforceable."

What follows immediately, and what does not?

It follows that no enforceable agreement is one without consideration. This is conversion of an E proposition, at sequence 450.

It follows that all agreements without consideration are unenforceable. This is obversion, at sequence 460.

It follows that it is false that some agreement without consideration is enforceable. This is inference by opposition, since the two are contradictories.

It does not follow that all agreements with consideration are enforceable. Nothing in the premise mentions agreements with consideration, and this is the error the distribution rule catches.

It does not follow that there are any agreements without consideration. On the modern reading a universal asserts no such thing, as sequence 380 established.

The point of the exercise. Five candidate conclusions, three good and two bad, all drawn from one sentence and no facts whatever. That is what immediate inference is for, and the rest of the module is the machinery for deciding which is which.

Distinctions that carry marks

What this does not mean

"Immediate" does not mean quick or obvious. It means without a mediating second premise. Full inversion, at sequence 490, is an immediate inference and takes five steps to derive.

Immediate inference is not trivial because it adds no information. Restating a provision in an equivalent form is exactly how a lawyer discovers what it does and does not say.

Mediate inference is not absent from law. It is everywhere; it is simply examined in the next Logic paper.

Quick revision

Immediate inference: one premise, no other proposition brought in.

Mediate inference: two or more premises, the conclusion following only from their combination. The classical form is the syllogism.

The syllogism is Logic II and is not on this paper. What carries forward is that its rules are rules about distribution.

Module III is entirely immediate: opposition at 3.2, eduction at 3.3, four further inferences at 3.4.

Opposition relates two propositions; eduction transforms one.

Why it matters: it is what can be concluded from a provision before any facts are known.

Test yourself

1. Define immediate and mediate inference and give an example of each.

An inference is immediate when the conclusion is drawn from a single premise with no other proposition brought in: from "all contracts are agreements" one may infer immediately that some agreements are contracts. It is mediate when the conclusion follows only from two or more premises taken together: from "all contracts are agreements" and "all agreements are promises" it follows that all contracts are promises, and neither premise yields that conclusion alone.

2. What is a syllogism, and is it examined on this paper?

A syllogism is a mediate inference consisting of three propositions and three terms, in which the two premises share a term that does not appear in the conclusion, and that shared term is what connects them. It is not examined on this paper: Module III is entirely immediate inference, and the syllogism, with its figures, moods and rules, belongs to the Semester 4 Logic paper.

3. Distinguish inference by opposition from eduction.

Opposition is a relation between two different propositions that share the same subject and predicate terms, and it asks how the truth value of one bears on the truth value of the others. Eduction is an operation performed on a single proposition, transforming it by changing the position or the quality of its terms, and it asks whether the resulting proposition is entailed by the original.

4. Does immediate inference add to our knowledge?

Not in the sense of supplying information the premise did not contain, since the conclusion is drawn out of the single premise. It is nevertheless useful, because restating a proposition in an equivalent form is often what reveals what it does and does not say. A section read in one direction can look like an authority for a proposition it does not support, and the operations of this module are how that is detected.

5. From "No suit shall be entertained unless notice has been given", state two conclusions that follow immediately and one that does not.

It follows that every suit entertained is one in which notice was given, and that it is false that some suit is entertained without notice. It does not follow that every suit in which notice was given shall be entertained, since the provision speaks only about suits without notice and says nothing about the rest. That last error is the commonest misreading of a provision of this shape.

6. Why is "immediate" not the same as "obvious"?

Because it describes the number of premises and not the difficulty of the step. An inference is immediate when it needs no second premise, however many operations it takes to get from the one premise to the conclusion. Full inversion is an immediate inference and requires a chain of conversions and obversions to derive, while some mediate inferences are seen at a glance.