Argument from converses

You support a claim by stating the same relation from the other end: if one party did the giving, the other party did the receiving. The argument works because the two subjects and the two predicates are converse pairs that describe a single relation, so asserting it from one side is the same as asserting it from the other. It can be attacked by showing that the two predicates are not true converses — that one side of the relation can hold without the other.

Example

The tenant must have received the notice, because the landlord sent it.

Standardised form

The tenant (a) must have received the notice (X) because the landlord (b) sent the notice (Y).

Transformations applied: anaphora resolved — “it” replaced by “the notice”.

Classification

Both the subjects and the predicates differ, so the argument form is gamma (a is X because b is Y).

The relation between the subjects “the tenant” and “the landlord” is the same as the relation between the predicates “received the notice” and “sent the notice”, so the argument substance is i.

The keyword CONVERSE describes the relation that the subjects and the predicates both instantiate. The argument lever can thus be formulated as “The landlord (b) is the CONVERSE of the tenant (a), as sending the notice (Y) is the CONVERSE of receiving the notice (X)”.

Not to be confused with

• Argument from opposites — The matching relation is opposition, not conversion: peace and war exclude each other, while sending and receiving complete each other. OPPOSITE
• Argument from derivatives — The two terms are grammatical forms of one word, not two ends of one relation. DERIVATIVE
• Argument from synonyms — The two statements mean the same thing said twice; here they describe one relation from two positions. SYNONYMOUS
• Argument from effect — Read as an alpha argument about the notice alone, the sending would be the cause of the receiving. EFFECT

Source

Invented example.

Notes

This is a proposed type that is not part of the current table of forty-two. It fills the slot left open in the Gamma quadrant by Aristotle’s list of topics: the Topics and the Rhetoric treat synonyms, opposites, inflections and correlatives (ta pros ti) as one family, of which the table currently contains the first three. The type is named after the converse relation that its subjects and predicates instantiate, rather than after Aristotle’s “correlatives”, to keep it apart from the argument from correlation.