What is Occam's Razor?

Mary McMahon
Mary McMahon

Occam's razor or the law of parsimony is a concept which is embraced by some people in the sciences, philosophy, and the broader humanities. Simply put, Occam's razor states that the simplest theory is often the best, suggesting that nature uses the simplest means to an end. Occam's razor is often used to reduce the number of competing theories under discussion, but it is important to remember that it does not actually rule out a theory, as you need empirical evidence to prove or disprove something.

Occam's Razor is illustrated in the saying, "When you hear hoofprints, think horses, not zebras."
Occam's Razor is illustrated in the saying, "When you hear hoofprints, think horses, not zebras."

The saying “when you hear hoofbeats, think horses, not zebras,” is a classic example of Occam's razor, and it also illustrates the weakness of this theory, since of course if one is in Africa or on a zebra preserve, the opposite of this statement would be true. In this instance, additional empirical information about the location of the hoofbeats and ideally observation of whatever is creating the sound is necessary before the presence of zebras can be disproved.

This theory is quite ancient, and it was commonly used in medieval philosophy. It is named for William of Ockham, who appeared to use the concept a great deal, although he most certainly did not invent it. Ockham also did not use the theory without criticism; several of his contemporaries pointed out that a reduction to the simplest answer was not always the best solution. Modern scientists have also suggested that nature seems to abhor simplicity, sometimes coming up with incredibly complex ways to accomplish simple things like fertilization of a flower.

Many people use Occam's razor to eliminate a competing theory when they are given a choice between a theory which suggests the presence of an additional entity and one which does not. The goal is to make as few assumptions as possible, and in the process hopefully come up with a workable answer to a problem or question. For example, at one point the field of physics relied on an “ether” to explain how light traveled. The existence of this ether could not be proved, and when Einstein suggested his Theory of Relativity, he did away with the ether altogether, positing a clear and simple theory which was deemed to be the best theory because it did not rely on the existence of a nebulous “ether.”

While the goal of reducing assumptions and trying to draw conclusions on the basis of what is actually known is certainly admirable, it is important to remember that reductionism is not always the best solution to a problem. Occam's razor is certainly a valid tool in the sciences and philosophical discourse, but it is not the only tool, and it is certainly not infallible. Reductionist arguments supported by Occam's razor may fall apart without supporting evidence.

Mary McMahon
Mary McMahon

Ever since she began contributing to the site several years ago, Mary has embraced the exciting challenge of being a wiseGEEK researcher and writer. Mary has a liberal arts degree from Goddard College and spends her free time reading, cooking, and exploring the great outdoors.

You might also Like

Readers Also Love

Discussion Comments


Actually what William of Ockham said in his literary works was that "entities should not be multiplied unnecessarily." I think that Occham's ideas were expanded greatly by other scientists and philosophers which resulted in the theory that is called "Occam's razor" today.

Technically, Ockham never said that the simplest explanation is the best or most accurate. He just said that explanations should not be multiplied and made complicated when it's not necessary.

What I understand from this is that ideas and theories should remain as simple as possible, granted that they properly explain something. If a simple theory cannot explain something, then it can be multiplied in order to reach a suitable explanation.


@Grivusangel-- I'm not sure if your example works well as an example of Occam's razor because the reason for a murder can determined in a definite way. The murderer can explain what the reason was.

I think that Occam's razor applies more to issues that are difficult to explain, or where there is no definite answer. When there are two possible explanations for a phenomenon where neither can be proven to be correct, Occam's razor theory says to go with the simpler one. So it can apply to any theory about sciences, logic or philosophy.

You have understood the theory correctly though. Occam's razor does say that the simplest explanation is probably accurate.


I'm not very familiar with this theory, it was not something that we discussed in philosophy class. But I think that it makes a lot of sense. Why seek a complicated explanation for something if it can be explained in a simpler way?


The Occam's razor theory is one I've found very workable, and frequently, correct. It's not necessarily because nature takes the simplest route, but because human reasoning is frequently pretty predictable.

For instance, when a murder is committed, the police look for motive, means and opportunity. At least half the time, the motive goes back to either money or a bad love affair. These are what most frequently move humans to commit murder, so investigators look at personal relationships and finances first. Occam's razor says the simplest explanation is often the right one. Murders are often simply about love or money -- or both.

Post your comments
Forgot password?