What philosophical “blade” encourages one to prefer simple explanations when they fit the evidence?
Answer by Jürgen Lawrenz
The “blade” you refer to is called “Occam’s Razor”. It is the name given to two arguments by the English scholastic thinker William of Ockham which stressed the “principle of greatest economy” in the search for truth and insight.
The first of these says:
It is pointless to do with more that can be done with less.
The other points out that:
A plurality should not be assumed without necessity.
Both these sentences are essentially warnings of the dangers of multiplying hypotheses to bolster a proof. An hypothesis is not a certainty; therefore five hypotheses will only render a proposition more uncertain and dissipate focus on the essence of an issue.
In addition, hypotheses are often framed with special nomenclatures requiring a definition, which is tantamount to a separate proof. But if only one of these is uncertain, then the whole ensemble is impaired.
Ockham, who was born in the 13th century, was targeting primarily the reliance of theological “proofs” on syllogistic principles. This method, he said, rests on confusion between concept and denotation — the first is a creature of the mind whereas the other points to something in the world. In metaphysical speculation, however, they are of equal value; therefore syllogisms which rely on supernatural causes run their course without contradiction and end up “proving” arguments that are plain nonsense.
There is a nice little book on this by Stephen Tornay: Ockham Studies and Sketches. It goes almost without saying that the march of science since the 18th century relies altogether on “Occam’s Razor”; it is nothing less than the First Commandment of scientific research.