In geometry, the law of detachment is a form of deductive reasoning in which two premises in relation to the same subject are examined to come to a reasonable conclusion. This law considers a hypothesis made with regard to a statement and uses deductive reasoning to find a true answer.
The "if" part of the law of deductive reasoning is always a hypothesis or a reasoned guess. The statement made after "then" is the conclusion. This is also referred to as a conditional statement. The hypothesis must be proven to be true in order for the conclusion to be true as well. Another example of the law of deductive reasoning would be:
- All mammals have fur
- All cats have fur
- All cats must be mammals
If the conclusion is false and the hypothesis is true in a conditional statement, then the conditional statement itself is false. A converse statement in the law of detachment happens when the hypothesis and the conditional statement are reversed. In the given example, the conclusion that all cats must be mammals would remain true.