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Originally Posted by NotReady
The issue isn't whether Platonism makes sense but whether, given that it's true, do logic, etc., make sense.
Here is the section you quoted, which shows that this is exactly what I said:
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Originally Posted by Original Position
If I can show that logic, morality, and science do make sense on a non-theistic basis like Platonism, then this premise would be false
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If, in some possible world, abstract logical rules are real objects, are they a sufficient foundation so that logic itself makes sense(is rational)? Van Til has an excellent discussion of Plato in which he shows why realism can't account for logic. One way he stated it in general was that if you place yourself, for argument's sake, on the position of the unbeliever and accept all his premises as true, does that account for rationality.
In philosophy of logic and maths, platonism refers to the view that there are actually existing abstract objects that are in some sense mind-independent (i.e. that do not exist solely as something being thought of by some mind.). The attraction of this view is that it gives us a relatively clear way of saying how it is that foundational logical or mathematical claims are true--they are true in a way roughly analogous to how claims about physical objects are true. If you accept a correspondence theory of truth, this means that they are true if in some way the claims about logic correspond to reality, i.e. accurately describe the properties of the abstract objects of logic/math.
So, if this theory is true, then logical claims make sense (they refer to the abstract logical objects) and have a truth-value. Now, let's take Van Til's thought experiment here and place ourselves in the position of the unbeliever that accepts platonism and ask whether that accounts for logic. Well, since his platonism gives an account of the meaning and truth of logical claims (the account I gave above), it certainly makes sense. So where is the argument that a non-theistic platonism cannot account for logic?
Just as a general note, rather than just telling me that Van Til has an excellent discussion of Platonism, just tell me his criticism of Plato. Having an excellent discussion of Plato doesn't make Van Til very unique--probably no one in philosophy has been as discussed. I'm more interested in how he actually shows that Platonism doesn't work to justify logic even if true.
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A word on abduction. If one surveys all the possible candidates for the foundation of rationality(in logic, morality, etc.), such as TAG, Plato, etc., it then becomes a question of which is the most plausible. Say, for instance, TAG is 51% and Plato is 49% - not the truth of the argument, but given its truth, what are the scope and explanatory power of the arguments, then abduction would say pick TAG.
TAG is not an abductive argument. I already explained this in my prior post. If TAG is sound, then the probability that platonism explains logic is 0%.
Look, you clearly have an argument in mind here. You think that God provides the best explanation for the intelligibility of the world, morality, and so on. Fine. There is an argument to be made for that conclusion. But, TAG is not it.
So here is the moral argument as presented by W.L. Craig:
1. If God does not exist, objective moral values and duties do not exist.
2. Objective moral values and duties do exist.
3. Therefore, God exists.
This is a TAG style argument. But it is
not an inference to the best explanation--it states absolutely that if God doesn't exist, then objective moral values and duties also do not exist. It is not saying that there are a menu of of options for explaining objective moral values and duties and the theistic one is the best (note that in
this article Craig explicitly contrasts his formulation of the moral argument with another version of the moral argument formulated as an inference to the best explanation.).
It is Craig's version of the moral argument that I find so objectionable (and the TAG-style arguments). I think the abductive versions, such as some of the
arguments here, much more reasonable and worth discussing.