(also known as: converse error, fallacy of the consequent, asserting the consequent, affirmation of the consequent)

**New Terminology:**

Consequent: the propositional component of a conditional proposition whose truth is conditional; or simply put, what comes after the “then” in an “if/then” statement.

Antecedent: the propositional component of a conditional proposition whose truth is the condition for the truth of the consequent; or simply put, what comes after the “if” in an “if/then” statement.

**Description:** An error in formal logic where if the consequent is said to be true, the antecedent is said to be true, as a result.

**Logical Form:**

If P then Q.

Q.

Therefore, P.

**Example #1:**

If taxes are lowered, I will have more money to spend.

I have more money to spend.

Therefore, taxes must have been lowered.

**Explanation:** I could have had more money to spend simply because I gave up crack-cocaine, prostitute solicitation, and baby-seal-clubbing expeditions.

**Example #2:**

If it’s brown, flush it down.

I flushed it down.

Therefore, it was brown.

**Explanation:** No! I did not have to follow the, “if it’s yellow, let it mellow” rule -- in fact, if I did follow that rule I would probably still be single. The stated rule is simply, “if it’s brown” (the *antecedent*), then (implied), “flush it down” (the *consequent*). From this, we cannot imply that we can ONLY flush it down if it is brown. That is a mistake -- a logical fallacy.

**Exception:** None.

**Tip:** If it’s yellow, flush it down too.

**References:**

Jevons, W. S. (1872). *Elementary lessons in logic: deductive and inductive : with copious questions and examples, and a vocabulary of logical terms*. Macmillan.