230. A few notes on Ockham’s Razor

One of the more enduring and influential principles of explanation is associated with the medieval philosopher William of Ockham (c 1280-1349) and is widely known as “Ockham’s Razor.” This principle prescribes that, if we are confronted with competing explanations that can all account for the phenomena we want to explain, then we should pick the explanation that is simpler: we should “shave off” all that is not needed.

Two things should immediately be mentioned by way of clarification. First, as the Internet Encyclopedia of Philosophy’s entry on Ockham points out, “Ockham’s Razor is the principle of parsimony or simplicity according to which the simpler theory is more likely to be true. Ockham did not invent this principle; it is found in Aristotle, Aquinas, and other philosophers Ockham read. Nor did he call the principle a “razor.” In fact, the first known use of the term “Occam’s razor” occurs in 1852 in the work of the British mathematician William Rowan Hamilton. Although Ockham never even makes an argument for the validity of the principle, he uses it in many striking ways, and this is how it became associated with him.”

Second, it is important to keep in mind that the use and success of the Razor need not imply that the world is simple (sometimes referred to as ontological simplicity). The Razor as Ockham employed it prescribes simplicity as far as theories, hypotheses, and other explanatory material are concerned (sometimes referred to as semantic simplicity). So advocating simplicity as far as explanations go need not commit one to reducing the entities or kinds of entities that exist in the world. That said, most would say it is desirable to have a view of the world with as few kinds of entities as possible. For example, materialists, for whom all reality is matter, would seek a view which excludes immaterial things such as souls, numbers, God, and so on. Others might include immaterial entities if they think they cannot adequately make sense of our experience with material entities alone. But both groups would be trying to keep it as simple as possible in terms of the entities they postulate.

Now, why we would we believe in this principle? One reason for embracing simplicity is aesthetic: the elegance, or even beauty, of parsimonious theories is often seen as an indication (not necessarily a guarantee) of their truth (see this PBS episode of Space Time for some interesting examples). Perhaps a better reason is this: if we are trying to understand something we should try to avoid introducing more complexity into the world that we may, in turn, have to explain. This would be self-defeating. And an even better reason is that a simpler hypothesis has less information and thus fewer ways to be wrong. The more factors involved in an explanation the higher the probability for error. 

William of Ockham

However, as the IEP entry on Ockham points out, there are those who object to the Razor:

“Nevertheless, not everyone approves of the razor. Ockham’s contemporary and fellow Franciscan Walter Chatton proposed an “anti-razor” in opposition to Ockham. He declares that if three things are not enough to verify an affirmative proposition about things, a fourth must be added, and so on. Others call Ockham’s razor a “principle of stinginess,” accusing it of quashing creativity and imagination. Still others complain that there is no objective way to determine which of two theories is simpler. Often a theory that is simpler in one way is more complicated in another way. All of these concerns and others make Ockham’s razor controversial.”

These are all important objections. But in the end it is important to keep in mind that the Razor isn’t being offered as a means to guarantee anything. It is a guide to what is more likely to be the case. This goes for other principles of good explanation as well. For example, alongside simplicity we often see the following guidelines:

Scope—pick the explanation that can explain more, rather than less, of what we want explained.  

Consistency—pick the one whose formulation is free from logical contradictions.

Coherence—pick the one that coheres or is consistent with what we already know.

Fruitfulness—pick the one that not only explains something at hand but promises to also explain other similar situations as well, that is, the one which bears fruit over time.

Falsifiability—pick the one that can be tested, the one that provides a way to falsify it. Without this factor hypotheses and theories become “closed”, like a conspiracy theory, which are immune to criticism (see my post on closed theories here). No matter what evidence you bring against a conspiracy theory the person maintaining it will have a way to avoid refutation (for example, if someone claims the government is manipulating all information, and you bring evidence that they are not, they will say that evidence itself is manufactured by the government). But this opens us up to the risk of maintaining false explanations with no way to self-correct since all contrary views are silenced.

These are all very helpful guides but they are just that: guides. In the end we try and use these guides to resolving problematic situations in ways that make life more successful and enjoyable. Many claim the Razor works. Indeed, in his A Brief History of Time (Bantam Books, 1988) Stephen Hawking attributes the discovery of quantum mechanics to Ockham’s Razor! But others may disagree (for examples see this paper which explores whether or not the Razor is a methodological principle of science). If you have employed it I am sure you have your own testimony to offer. If you haven’t employed it then perhaps you can try it and see what happens.

For my post on determinism, which features the idea of simplicity with reference to debates between materialism and dualism, go here.

2 replies on “230. A few notes on Ockham’s Razor”

  1. I may set forth the proposition that the razor is a built-in cognitive faculty, for all explanations at which we arrive through interpretation of sensory experience are based upon highly filtered data that has been “shaved” by the presumably meaningful limitations of sensory organs. It doesn’t matter so much that part of the process is unconscious if we take cognition generally to be the whole thing–from transduction of physical phenomena into electrochemical signals on the occasion of sense straight up to conscious awareness and reasoning based upon the transduced data. This idea may not pertain to the application of the principal of parsimony to explanations of “things” that are not actually observable physical occurrences out there in the world. But does the principle actually apply to that sort of explanation, like explaining what an “idea” is?

    • Dwight Goodyear on

      Hey Geoff, thanks for the comment. I have a few things in response.

      1) To think of the razor as a “built-in cognitive faculty” is interesting but I think it would be a category mistake since the razor is a prescription for theory choice whereas the functioning of cognitive faculties, the way you are describing it, wouldn’t seem to be theoretical at all. Nietzsche had long claimed that our faculties simplified perception in order to help us survive. He even claimed the laws of logic and mathematics were an outcome of this simplification that conferred an evolutionary benefit which, however, falsified everything. Now, such evolutionary developments wouldn’t be in the realm of theory choice – in fact, they wouldn’t have any purpose or meaning at all nor would they be a function of choice if we follow modern evolutionary theory. So if that’s how you are thinking about the issue, and it seems you are since you include unconscious processing, then I think my point applies.

      2) I also think it is problematic to claim that our faculties simplify things in a way that results in “all explanations” being affected. For how would you be able to get into a position to know the complexities out there in the world and compare the results of our simplifications to it? If you have a set of razor faculties (as it were) could you really use them to understand THEIR limits at all? How would you have the insight you share about them affecting all our explanations? It seems you are making an objective claim about our mind and its relation to the world which, if true, would itself be exempt from a radical misinterpretation by faculties that simplify everything. I am more inclined to embrace a view of our faculties that avoids this problem and gives us a way to access truth. We can certainly accept that we know from a perspective and that our subjectivity is ingredient in our understanding of the world. But from the fact that we know from a perspective it doesn’t follow that we can’t know the truth about at least some facts.

      3) You ask whether the razor applies to the kind of explanation you make about what an idea IS. I would say, similar to (1) above, that the razor isn’t primarily a theory about the nature of ideas or things in the world as such; it is a prescription about what theories/hypotheses we should adopt about such things. Metaphysics is concerned with what exists and how to characterize what exists (objects? Numbers? Ideas? Immaterial things? Material things? God? etc.). But the razor can help us when we are confronted with competing metaphysical theories. As I said in my post, “materialists, for whom all reality is matter, would seek a view which excludes immaterial things such as souls, numbers, God, and so on. Others might include immaterial entities if they think they cannot adequately make sense of our experience with material entities alone. But both groups would be trying to keep it as simple as possible in terms of the entities they postulate.”

      Anyway, I hope that helps a bit – let me know if you have any more questions or comments.

Leave a Reply

Your email address will not be published. Required fields are marked *

This site uses Akismet to reduce spam. Learn how your comment data is processed.