First off, an 'argument' isn't an argument in the same way as a shouting boyfriend and girlfriend disagreeing on who's turn it is to wash the dishes is. A philosophical argument is like a theory which is backed up by reasons to think that the theory is true.
Here's one that's a theist favourite: The Kalam Cosmological Argument, as made famous by William Lane Craig.
P1: Everything that begins to exist has a cause.
P2: The universe began to exist.
C: The universe has a cause.
The 'P's are called premises. The 'C' is the conclusion.
There are two things to think about when working with one of these arguments.
First we look at whether the argument is sound or valid. This means that we have to figure out if the C is what definitely follows if the Ps are true. It's a bit like maths. Does P1+P2=C in the same way that 2+2=4? That's not algebra, that's just figuring out the logic of the argument.
In the case of the Kalam it seems obvious that C is the inescapable conclusion of the two Ps if they are true.
Here's a simpler one that doesn't need you to have any cosmological knowledge!
P1: All apples are fruit.
P2: All Granny Smiths are apples.
C: All Granny Smiths are fruit.
So if Granny Smiths are apples, and all apples are fruit, then it's obvious that Granny Smiths are fruits! Simple.
P1 is a true statement. We know that apples are a type of fruit. P2 is also true. We know that Granny Smiths are all apples. So C is unavoidably true.
But hold on! What about the iPhone? That's an apple. That's not a fruit. What about the old lady that lives down the street? That Granny Smith isn't an apple.
This is why definitions are really, really important. If you're presenting an argument like this, part of your backup support to each premise has to be a clear definition of what you are talking about. So as long as it's clear that by 'apple' we mean the green or red things that grow from certain trees, and 'Granny Smiths' are a specific product, we should be safe to say that 'C' is true.
With that in mind have a look at this:
P1: All apples are fruit.
P2: All iPhones are apples.
C: iPhones are fruit.
The argument looks sound (as in C would follow if P1 and P2 were true) but it fails because of a logical fallacy. Logical fallacies are basically failures in logic. The logical failure here is called 'the fallacy of equivocation'. This means that in one of the 'P's, one definition of 'apple' was used, while in the other 'P' a different definition of 'apple' was used. Because the argument has a logical fallacy, that means it isn't sound.
If it's not sound, we can ignore it completely.
Here's another example of an argument that isn't sound:
P1: All loud noise after midnight is bad.
P2: Bars make loud noise.
C: Bars must be closed by midnight.
Let's just for the sake of argument say that P1 and P2 are true statements (they aren't but let's pretend for the example). You could say P1+P2=C, but it turns out, you don't have to. There are missing alternatives. You could put in "P3: Bars are incapable of being quiet." If P3 was also true, then maybe 'C' would follow. As the argument stands though, the C that follows from P1 and P2 could equally be "C: Bars must stop making loud noise by midnight". If P1 and P2 could mean something different to C, then the argument is not sound (valid).
So a quick checklist of some simple things you can look for to make sure an argument is sound. There are more fallacies out there you can look into, but you don't really need to know all their names if you can spot a logical mistake:
- The C logically inescapably follows from the Ps almost like a maths equation.
- Clear definitions that don't change part way through.
- No missing premises.
At this point you look at each P on its own and see what evidence there is to back it up. I'm not going to go into that here for Kalam, because this post is just explaining how arguments work.
Here's an example of a popular atheistic argument:
P1: An all loving, all powerful God would not allow evil to exist.If this is your first look at philosophical logical arguments, I wouldn't be surprised if you can't see the problem with this one. There was a time when this troubled me too.
P2: Evil exists.
C: An all loving, all powerful God does not exist.
We find the problem with this argument when we look into whether or not the P's are true.
P1 fails simply because it isn't more likely true than false. Where P1 fails is that it ignores the possibility that an all loving, all powerful God might have a reason to allow evil to exist that leads to some greater good. As long as that is a possibility, then we can't say that P1 is definitely true or even more likely to be true. So to make P1 true, or at least more likely to be true, an atheist would have to somehow show that God has absolutely no reason to allow evil to exist - which is impossible.
Look at it this way: We have two options here
- An all loving, all powerful God would not allow evil to exist.
- An all loving, all powerful God would allow evil to exist.
There are several other possible reasons why God would allow evil, and they add up to there being no good reason to think that P1 is true.
P2 has its own problems, but seeing as one of the premises of the argument doesn't work, then the entire thing crumbles.
There's a bit of a difficulty here in that some people might think that if a premise is not definitely true, then the argument is debunked. (debunked means disproved, or that we can ignore it) That's not the case.
Arguments (just like scientific theories) are about finding an answer that is the best fit considering the information that we have. If an argument's premises and conclusion are more likely to be true than false, then we have good reason to believe it.
In the above example, the argument is debunked because we have no good reason to think P1 is true. There's no contradiction between a loving God and the existence of evil, so the conclusion just doesn't follow.
Going back to the Kalam, several people have claimed to have debunked it. That's not remotely true.
There are objections and rebuttals to consider, but the Kalam is still sound and most likely true.
So to recap:
A philosophical argument is a bit like a sum where every P (premise) has to logically add up to a C (conclusion).
Each P has supporting information and evidence. The P is usually a short sentence summary of all of it.
The conclusions of philosophical arguments usually go to show that something is more likely to be true than false (just like scientific theories).
To disprove a philosophical argument you either have to show that the P's do not add up to the C, or show that at least one of the P's is more likely false than true.