Given that an individual's presence at the scene of the crime is required in order for that individual to commit the crime, the use of alibis, or evidence of suspects being somewhere other than the crime scene at the time of the crime is an example of what sort of proof?
A) Proof by induction
B) Proof by transposition
C) Direct proof
D) Inductive reasoning

Question

Quizplus · Accepted Answer

Proof by transposition works by showing that if a certain condition were true (in this case, the suspect committing the crime), then a specific outcome must necessarily follow (the suspect being at the crime scene). By presenting an alibi, the argument is made in reverse to show that because the specific outcome (presence at the crime scene) did not occur, the initial condition (the suspect committing the crime) must also not be true. This is a classic example of proof by transposition, also known as proof by contrapositive.

Given That an Individual's Presence at the Scene of the Crime