Ockham's Razor.

[The Duchess of Zeon]

The famed razor of Ockham, in fact being of two parts, and originally a principle of logic included in the Summulae logicales of Peter of Spain, later Pope John XXI, is as follows: Nunquam ponenda est pluritas sine necessitate; or: "Plurality is not to be posited without necessity." The second part being: Frustra fit per plura quod potest fieri per pauciora; or: "What can be explained by assuming fewer terms is vainly explained by assuming more."

William of Ockham, the famous nominalist, was of course the first to make a virtue of being "fanatical" about logic; and these are the exact terms of his razor that he used to cut through the arguments of the more unwieldy world-views of his theological debating foes, who gave to God a more active and extreme position in the animation of the world and of reason.

I thought it might be of some interest to post the original versions.

[The Dark]

For those interested in reading more about the razor of the Franciscan Monk and philosopher William of Ockham, the Skeptic's Dictionary has a website devoted to it at http://skepdic.com/occam.html

Some basics:
William of Ockham lived from 1285-1349. He was a theologian and philosopher who was attempting to reconcile religious belief with rationality. He eventually declared that religion could not be rationally proven and was a matter of faith, contrary to popular belief at the time. He is considered to be one of the founders of scientific inquiry. While Duchess' translations from Latin are good, I found slightly different ones:
"Plurality is not to be assumed without necessity"
"What can be done with fewer is done in vain with more." *Note: the "fewer" is intended to refer to assumptions only.

I also found a third quote purporting to be part of Ockham's razor, namely non sunt multiplicanda entia praeter necessitatem, or "entities are not to be multiplied beyond necessity." However, this was written by a later scholar attempting to sum up the first two principles, and is somewhat less clear than the first two.

According to Paul Gibbs (at http://hepweb.rl.ac.uk/ppUK/PhysFAQ/occam.html), the law of parsimony is a stronger version of Occam's Razor, still valid, but occasionally overused. "The principle of simplicity works as a heuristic rule-of-thumb but some people quote it as if it is an axiom of physics. It is not. " Paul Dirac did not like the law of parsimony, stating that sometimes the beauty of the universe must win out over simplicity. The basic idea is to use the Razor whenever something is clearly unnecessary. However, "[t]he law of parsimony is no substitute for insight, logic and the scientific method. It should never be relied upon to make or defend a conclusion. As arbiters of correctness only logical consistency and empirical evidence are absolute."

[Darth Wong]

The general concept is that the theory which uses fewer terms is superior. That does not guarantee that it is correct.

Ergo, the statement "the simplest theory is always right" is incorrect. However, the statement "given two theories of equal performance, the simpler theory is better" is correct, assuming we understand the definition of "simpler" in this context.

People get all pissy because they believe that you can't state something as a fact unless it has been absolutely proven. However, since nothing has been absolutely proven, this argument leads to the preposterous conclusion that nothing should be stated as fact. Occam's Razor is a way of determining which theories make more sense, rather than proving that anything is absolutely correct or incorrect.