Why Validity Matters

In this post, we will briefly consider two famous arguments that are in need of lots of interesting work to make them valid and persuasive. Rather than do that work here, I just want you to see the original arguments and how you are now in a good position to see their defects as stated. I am not saying that they cannot be remedied. But the attempted remedies are trickier than meets the eye. Put differently: once we recognize that the original arguments are not valid, the force of the arguments begins to diminish a bit. 

The Logical Problem of Evil
Lots and lots of people think that the existence of evil is a real problem for the existence of God. But clearly stating the problem is not as easy as some have thought, and once the problem is clearly stated the ways out of it are more numerous than initially believed. Here's a first stab at the problem:

1st try: Evil exists. Therefore, God does not exist. 

Obviously, that won't do. Something else must be added. But what?

Someone might try this:

2nd try: Evil exists. If God exists, evil should not exist. Hence, it is false that God exists.

That won't do either. the conclusion does not follow. The argument is invalid. 

Do you see why?

3rd try: Evil exists. If God exists, evil does not exist. Hence, it is false that God exists. 

Ok, we now have a valid argument. But, now the second premise looks suspicious. Why should anyone accept it? So, now we need an argument for the second premise and that argument won't be as simple as we might have thought. 

Lesson: Logic can help us see what steps are needed to get to a conclusion and it can help us see which of those steps are weak--weaker than we might have first thought. 

The Freedom and Foreknowledge Problem
Lots and lots of people think that free will is incompatible with divine foreknowledge (How can I act freely when God allegedly knows what I will do prior to my doing it?). But once again clearly stating the problem is not as easy as some have thought. Here's a first stab:

1st try: God knows the future exhaustively. At some future time, Frank freely eats pizza. Therefore, either it is false that God knows the future exhaustively or it is false that at some future time, Frank freely eats pizza. 

Obviously, that won't do. Something else is needed to show the alleged inconsistency. But what?

2nd try: God knows the future exhaustively. At some future time, Frank freely eats pizza. If someone does A freely, then she can do ~A freely. Hence, either foreknowledge is impossible or free action is impossible. 

Again, lots of problems here. One is that the argument is still invalid. How should we repair it?

Whatever repair we attempt it will become more and more clear that the argument is less obvious than we might have initially thought. 

Lesson: learning what validity and invalidity are and learning how to apply them to common arguments will help us understand all sorts of issues much more clearly. Indeed, it can help us clearly see how unclear much of our thinking often is. 

Thoughts?

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