[SEQ RERUN] A Priori
post by MinibearRex · 2011-09-21T03:42:58.591Z · LW · GW · Legacy · 8 commentsToday's post, A Priori was originally published on 08 October 2007. A summary (taken from the LW wiki):
The facts that philosophers call a priori arrived in your brain by a physical process. Thoughts are existent in the universe; they are identical to the operation of brains. The "a priori" belief generator in your brain works for a reason.
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This post is part of the Rerunning the Sequences series, where we'll be going through Eliezer Yudkowsky's old posts in order so that people who are interested can (re-)read and discuss them. The previous post was No One Can Exempt You From Rationality's Laws, and you can use the sequence_reruns tag or rss feed to follow the rest of the series.
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8 comments
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comment by [deleted] · 2011-09-21T14:06:49.481Z · LW(p) · GW(p)
Simpler explanations aren't more likely to be true, they're more likely to be simple. Occam's Razor isn't a fact about reality, it's just a restatement of what we're trying to do in science: make simplified models of reality.
"Occam's Razor works up to October 8th, 2007 and then stops working thereafter" isn't rejected for being more complicated, it is rejected because "October 8th, 2007" is not justified. Take Russel's chicken for example (The chicken is raised well and fed every day by a farmer, who suddenly, on October 8th, 2007 wrings the chickens neck and plucks its feathers out), it had no reason to run away on October 1st even though that would save its life: It would be a superstitious irrational chicken that ran away on the first of October for no real reason, but it would be a (hyper)intelligent one that figured out it was ripe for eating and left just in time.
Occam's Razor arose from the observation that lots of correct explanations are simpler than other, wrong ones - the simplest explanation of that is that "simplest explanations are more likely to be true" - but this is just another example where applying this principle leads one astray. Given any explanation you can find arbitrarily many more complicated and wrong ones, combine that with the wild creativity people have and it's no surprise we tend to overshoot.
So there is no need to try to justify this principle, instead realize why our explanations tend to be simple and reject it. It's not useful as a heuristic for finding correct explanations, the general method for that is something much more complicated.
edit Why not post objections instead of just downvoting?
Replies from: Jack, lessdazed↑ comment by Jack · 2011-09-21T15:47:44.653Z · LW(p) · GW(p)
Your claim that simplicity is not a useful heuristic for finding correct explanations strikes me as obviously wrong.
Replies from: None, pedanterrific↑ comment by [deleted] · 2011-09-21T16:29:19.807Z · LW(p) · GW(p)
but I even explained in my comment (paragraph 3) why the principle strikes one as immediately obvious, and why that first impression is mistaken.
Replies from: Jack, None↑ comment by Jack · 2011-09-21T16:44:45.008Z · LW(p) · GW(p)
Given any explanation you can find arbitrarily many more complicated and wrong ones, combine that with the wild creativity people have and it's no surprise we tend to overshoot.
Is a perfectly good justification for Occam's Razor.
ETA: I haven't downvoted you, btw. However, the karma for your comment might be improved if you paid more attention to things like run-on sentences which affect readability.
↑ comment by [deleted] · 2011-09-21T16:40:44.453Z · LW(p) · GW(p)
Out of curiosity, have you read Where Recursive Justification Hits Bottom? The explanation there is a little more thorough.
Replies from: None↑ comment by pedanterrific · 2011-09-21T16:10:08.930Z · LW(p) · GW(p)
↑ comment by lessdazed · 2011-09-22T08:24:25.674Z · LW(p) · GW(p)
Take Russel's chicken for example (The chicken is raised well and fed every day by a farmer, who suddenly, on October 8th, 2007 wrings the chickens neck and plucks its feathers out), it had no reason to run away on October 1st even though that would save its life: It would be a superstitious irrational chicken that ran away on the first of October for no real reason
There are many days on which it could be killed, and these events are mutually exclusive, so any particular detail will probably be false unless justified by evidence. Likewise for means of death, who will do the killing, and so on.
A much simpler hypothesis than "The farmer will kill the chicken, AND it will be on day X, where X is a day in October," is a similar hypothesis without the conjunction: "The farmer will kill the chicken."
"The farmer will never kill the chicken" is identical to "The farmer will not kill the chicken today AND the farmer will not kill the chicken tomorrow AND he farmer will not kill the chicken the following day..." This has many conjunctions, and consequently many opportunities to be wrong.