Occam's razor is a special case of a more general principle: that the least useful may be profitably discarded. This idea is associated with evolution via natural selection. In honor of Darwin, I propose that we call it "Darwin's razor".
Definition of "Darwin's razor": the least useful is best discarded.
Occam famously discarded all but the shortest hypothesis. However, from a more Darwinian perspective, that's often a bad idea. For one thing you lose a diverse breeding population of hypotheses. For another, it is harder to adapt if new observations no longer fit the previously-selected hypothesis. Lastly, if you only consider the shortest hypothesis, it turns out that you can't estimate probabilities correctly.
"Darwin's razor" represents the winnowing, destructive side of Darwin's theory. I've previously referred to this as being "natural elimination". Of course, Darwinism also has a creative side: the production of new forms. However, that is hardly well described as being like the operation of a razor. "Darwin's razor" is all about eliminating the old, the unwanted and the unfit.
Occam's razor famously had only one blade. Darwin's razor is more like one of those modern multi-blade razors. This analogy works in two ways:
- Occam's razor said to only keep one hypothesis, while Darwin's razor allows you to keep a breeding population of hypotheses;
- Occam's razor only applied to one thing: hypotheses, while Darwin's razor is a universal razor that can cut through practically anything.
- Wallet full of small coins? Apply Darwin's razor.
- Too much spam? Darwin's razor can help.
- Fridge full of useless jars? Darwin's razor works there too.
- Garden full of things you never planted? Use Darwin's razor.
Occam's razor has turned out to be a somewhat-inaccurate approach. However, Darwin's razor does a much better job of surviving critical scrutiny. It isn't possible to keep all unrefuted hypotheses around (as Solomonoff induction might suggest) because there isn't enough space in the universe. You have to discard something. Darwin's razor recommends discarding the least useful stuff. It's simple and pragmatic advice that's hard to disagree with. Darwin's razor.