Occam's Razor

By: Mike Gashler

Occam's Razor is almost ubiquitously understood to say, "simpler explanations are better". There's just one problem with this summary. And it's a pretty big problem. It's wrong!

Firstly, that's not even what Sir William of Ockham said. Occam's Razor states, "Non sunt multiplicanda entia sine necessitate." (Emphasis mine.) Those two underlined Latin words translate to "without need". So what he really said was, "Don't add complexities without need."

But that means pretty-much the same thing, right? No. Even more important than what Ockham actually said is what actually works. And reality is never simple. Ever! Any real thing is complex. If someone said reality is simple, every real thing that ever occurred would invalidate the statement.

Occam's Razor is about how to be effective in forming hypotheses, not about the nature of reality. And the main point is not even about simplicity. It's about avoiding unnecessary complexity. Let's compare:

Wrong	Right
The truth is probably something simple.	Don't add your biases to your explanations.
Complex and confusing things are probably wrong.	Keep your explanations opinion-free.
Reality isn't often complex.	Let the data speak for itself.
Too many details make explanations unlikely.	Leave your feelings out.
Simple explanations are more consistent with truth.	Don't make stuff up.

Notice that all the statements in the "wrong" column are about what is true. And all the statements in the "right" column are about what to do. Occam's Razor is not a statement about truth--what "is". Occam's Razor is a directive--how we "ought" to operate. If you try to reason across that gap, Hume's Guillotine will sever your philosophy!

The method Sir William of Ockham was describing is called abductive reasoning. It is still the most effective method known for learning. Is it true? No, but it's effective. It's not about what is true. It's about what works. Following the evidence works. Hiding from complexity does not.