Law of Detachment
The law of detachment (also known as affirming the antecedent and Modus ponens) is the first form of deductive reasoning. A single conditional statement is made, and a hypothesis (P) is stated. The conclusion (Q) is then deduced from the statement and the hypothesis. The most basic form is listed below:
- P→Q (conditional statement)
- P (hypothesis stated)
- Q (conclusion deduced)
In deductive reasoning, we can conclude Q from P by using the law of detachment. However, if the conclusion (Q) is given instead of the hypothesis (P) then there is no valid conclusion.
The following is an example of an argument using the law of detachment in the form of an if-then statement:
- If an angle A>90°, then A is an obtuse angle.
- A=120°
- A is an obtuse angle.
Since the measurement of angle A is greater than 90°, we can deduce that A is an obtuse angle.
Read more about this topic: Deductive Reasoning
Famous quotes containing the words law of, law and/or detachment:
“The so-called law of induction cannot possibly be a law of logic, since it is obviously a proposition with a sense.—Nor, therefore, can it be an a priori law.”
—Ludwig Wittgenstein (1889–1951)
““If the law supposes that,” said Mr. Bumble, squeezing his hat emphatically in both hands, “the law is a ass—a idiot. If that’s the eye of the law, the law is a bachelor; and the worst I wish the law is, that his eye may be opened by experience—by experience.””
—Charles Dickens (1812–1870)
“There is no detachment where there is no pain. And there is no pain endured without hatred or lying unless detachment is present too.”
—Simone Weil (1909–1943)