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An Evolutionary Argument For Naturalism


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Alvin Plantinga is famous for his Evolutionary Argument Against Naturalism, so I decided to turn it on its head.

A few probability rules:

P(A&B)=P(B&A)
P(A&B)=P(A|B)XP(B)

Substituting, we get: P(A|B)XP(B)=P(B|A)XP(A)

Rearranging, we get: [math]P(A)=\frac{P(A|B){\times}P(B)}{P(B|A)}[/math]

Plantinga tells us that if unguided evolution were true, then it is very probable that our ability to naturally come to true beliefs is unreliable. That is, P(T|U) is very very close to 1 (Plantinga wants it to be as close to 1 as possible if not 1).

It is, however, a fact that our ability to naturally come to true beliefs is unreliable. Our logical and probabilistic intuitions are very very bad. We can do these things, but it's very taxing compared to the way we naturally do things and it requires training to avoid fallacies. Even our memories of past events are unreliable. Even after learning how to do things the correct way and doing a lot of practice, we are still subject to the pitfalls that are collectively human psychology. So, if P(T) isn't 1, it is VERY close to it.

[math]P(U)=\frac{P(U|T){\times}P(T)}{P(T|U)}=P(U|T){\times}\frac{P(T)}{P(T|U)}[/math]

Since P(T) and P(T|U) are both incredibly high (both either 1 or so close to 1 as to effectively be 1), they effectively cancel.

That leaves P(U)≈P(U|T).

So, given the unreliability to naturally come to true beliefs, how likely is it that unguided evolution is true? Well, evolution itself is a fact so that rules out a lot of supernatural explanations. But would guided evolution be likely to give us such horrible mental faculties? I think Plantinga would say no. So, I'm going to put P(U|T) as very high. Thus, it is extremely likely that unguided evolution (read: naturalism) is true.

Edited by ydoaPs
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But would guided evolution be likely to give us such horrible mental faculties? I think Plantinga would say no

I don't really get this part. How reliable would guided evolution mental faculties be?

 

How could the existence of contradictory concepts even be explained in a world of people that have reliable mental faculties?

 

It seems like the whole argument relies on the opinion at the end being true? That the probability below isn't necessarily true?

 

 

So, I'm going to put P(U|T) as very high

 

Edited by jp255
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