Fallacious Use of Occam’s Razor?


Hi, I PMd you earlier but then saw your guidelines for a provocative title and to keep it short, so heres a repost!

I enjoyed your videos and appreciate the gentleness and respect with which it was done. I have a similar background to you (PhD in Adaptive and Neural Computation). Im a Christian; I’m not here to preach, but would take issue with you respectfully over your use of Occams razor to eliminate God. I think this is a fallacy.

The reason Occams razor is true is not because the mind will naturally prefer the explanation that makes the fewest assumptions. This makes it appear to be a subjective belief. There has to be a rational explanation of why it’s true & there is: it is because the simpler explanation is more _probable_ . (Seehttp://tinyurl.com/33fbmzx Fig 10.1 for an illustration of why this is so).

This is why, in your example of the fallen object in the closet (which I thought was a very nice example) you can eliminate the cat, because you can make an estimate of the probability of the cat slipping away scenario, and see that the object falling under gravity is much more likely. The reason you can make that estimate is that cats in cupboards are part of the natural world, obey natural laws etc.

However, if it comes to God, you are on different ground because God is not supposed to be part of the natural universe, but the creator of it, and definer of its laws, not subject to them. So you cant meaningfully assign a probability to God existing, and hence cannot meaningfully apply Occams razor to eliminate God.

What do you think? (More detail and courtesy in my other post!)


Hi. Thanks for reposting.

I would say that, in hindsight, both you and I have defined Occam’s Razor in a way that isn’t quite accurate in respect to its real value to scientific thinking. After having a long and useful discussion with GoforBroke on his video, I have come to the conclusion that the reason Occam’s Razor is valuable is because of its methodological robustness.

To clarify this point, let me use the example of heart failure that GoforBroke used in his video. Initially, the scientists used the simplest hypothesis they could to explain the available evidence. This was chosen because of the Occam’s Razor principle. Now, after testing their hypothesis, they discovered it was wrong. Their tests produced new evidence that forced them to restructure their hypothesis into a more complex one (but still the simplest possible via Occam’s Razor). This new, slightly more complex hypothesis turned out to be correct, in that it could explain the new evidence and produce accurate predictions for new tests.

My point here being that Occam’s Razor does not necessarily produce a more *accurate* hypothesis on its first application. Rather, the value of Occam’s Razor is that it is a tool that allows us to methodically reach the most accurate hypothesis as more evidence becomes available.

If the team had started with a more complex hypothesis, there is no analogous heuristic they could have used to formulate it and there would also be no analogous heuristic to trim it down after it failed based on new evidence (unless the group was willing to revert back to the use of Occam’s Razor, of course).

So we can say nothing of a hypothesis’s accuracy before we test it. All we can say is that, when we use Occam’s Razor, we have produced a hypothesis that is likely to lead us to the accurate hypothesis. And we have empirical evidence that structuring hypotheses using Occam’s Razor is likely to lead to the accurate hypothesis based on the many successful ventures of using it in science, as the heart team pursuing the heart problem did.

Now, let me return to your use of Occam’s Razor on the question of God’s existence. The problem with the way you have formulated your hypothesis is that you are assuming the supernatural exists. We don’t have evidence that necessitates a belief in the supernatural. Until we do find evidence for the supernatural, one is not justified to formulate a hypothesis involving it, due to Occam’s Razor.

The supernatural may exist. And someday we may find evidence for it. But until then, we are using the hypothesis that is most likely to lead to the correct answer. And that is not assuming the supernatural exists until we find evidence. Because that accounts for the other possibility that it does not exist at all.

In conclusion, by not assuming the supernatural exists, we leave ourselves open to:

1) Someday formulating a hypothesis that includes the supernatural because we find evidence for it

2) Never formulating a hypothesis that includes the supernatural because we never find evidence for it

Thus, however the universe *really* is (including a supernatural or not having one at all), our hypothesis either matches it now or will match it someday when we find the right evidence. Assuming the supernatural exists before we have motivating evidence for it would violate the possibility that there is none.

2 comments on “Fallacious Use of Occam’s Razor?

  1. FO says:

    That was just the ontological argument: “God has Property X”, “Property X implies existence” -> “therefore God exists”.

  2. Darrel Martin says:

    “So you cant meaningfully assign a probability to God existing, and hence cannot meaningfully apply Occams razor to eliminate God.”

    With the same reasoning, it seems you cannot meaningfully apply Occam’s Razor to demonstrate god, either. These arguments leave me wanting so much more. Apologists have plenty of scientific proofs for god, but as soon as an argument is turned on its head: god is suddenly outside of time, outside of our universe, not subject to our needs, and utterly unfalsifiable.

    I’m reminded of Carl Sagan’s famous chapter – The Dragon in my Garage:

    “Now, what’s the difference between an invisible, incorporeal, floating dragon who spits heatless fire and no dragon at all? If there’s no way to disprove my contention, no conceivable experiment that would count against it, what does it mean to say that my dragon exists?”

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