How To Apply Occam's Razor

One subtlety the video doesn't touch on is that the complications/necessary conditions being evaluated have to be independent. If an explanation has many necessary conditions, but they all arise from the same cause or are caused by each other, then they don't complicate the explanation. A thousand dominoes toppling over in a line does not require 1,000 separate, independent conditions, in order for "my finger pushed one over" to be the correct explanation for what happened. Abusers of Occam's razor sometimes supply a laundry list of supposed complications (trying to show that a rival theory is too complicated), but which all trace back, by cause-and-effect, to one event, the theory for which has only a few independent conditions.

Occam’s razor is a problem for pretty much all highly visible conspiracies that have purportedly been successful, because any conspirator at any time could come forward and blow the whistle, independently of the others. For the Moon landing to be a hoax, or the Earth is flat but there's a worldwide conspiracy of geologists and astronomers telling us otherwise, it’s just ridiculous.

More examples of applying Occam's razor:

You believe you saw your girlfriend kissing someone else on the street. She says she was hanging out with friends at the time. When you ask each friend, they all say the same thing. Perhaps they have made a pact to lie and tell the same story. But unless you have evidence that anyone is lying (other than your eyewitness account), Occam’s razor says the woman was most likely just someone else.

Many people believe they have been abducted by aliens during the night. Either beings from another planet physically visited their home and left no other trace other than memories, or it was just a very compelling lucid dream or a case of sleep paralysis, and it was all in their head. Of course, the latter is more likely to be true.

The “multiverse” proposal, that there exist universes outside our own, has been criticized for violating Occam’s razor. But its supporters claim it’s actually a less complicated theory. There are cases in science where similar “ad hoc” assumptions were later discovered to be correct; after Mendel worked out that physical traits are passed from parents to offspring, it was assumed there’s some biochemical mechanism responsible — and decades later, DNA was discovered. But if a theory hangs on a condition for which there is no direct evidence, we need to seek out that evidence, rather than accept the condition outright.

If you’re interested in a highly radical view of the universe that’s largely based on Occam’s razor, check out “The Simplest-Case Scenario,” which can be downloaded for free: simplestcasescenario.com.