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 world is nothing, the man is all; in yourself is the law of all nature, and you know not yet how a globule of sap ascends; in yourself slumbers the whole of Reason; it is for you to know all, it is for you to dare all.”
—Ralph Waldo Emerson (1803–1882)
“I wish my countrymen to consider that whatever the human law may be, neither an individual nor a nation can ever commit the least act of injustice against the obscurest individual without having to pay the penalty for it. A government which deliberately enacts injustice, and persists in it, will at length even become the laughing-stock of the world.”
—Henry David Thoreau (1817–1862)
“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)