How should we evaluate claims or arguments? Many times it can be difficult to see where to begin. I’m not sure there’s any one place that someone must start in evaluating claims. What follows, however, are some of my suggestions for evaluating claims. You may find one tactic or another helps clarify the issue. Clarity is always good, because it helps your response!
1. What is the claim stating?
This is important. If you are not even sure what’s being claimed, how can you refute (or accept) it? Here’s an example: “There’s no good evidence for God.” What does this mean? Does this mean there are no facts in virtue of which God’s existence is made more probable than without them? Does this mean there may or may not be such facts, but that one is not justified in accepting God’s existence on that basis? Does this mean there’s no scientific evidence for God? Does this mean that there are no facts in virtue of which it is rational to believe in God? For me, at least, whether or not I agree with the claim depends on which sense of the claim is meant: essentially, it depends on what the claim is actually stating.
2. What are the implications of the claim?
This usually comes after one understands the claim itself. It essentially asks, “What follows if the claim, as I understand it, is true?” Many times, this is unstated by the person making the claim. Sometimes this is because it is obvious. Other times the ambiguity helps: it might imply several objections without the person having to do any of the work. Suppose we understand the claim “there’s no good evidence for God” as meaning there’s no scientific evidence for God. What follows from that? Is it supposed to follow that God does not exist? Is it supposed to follow that one is unjustified in believing in God? Sometimes the claims are not ambiguous regarding their implications, but the claim just doesn’t have the implications the objector thinks it does.
3. What are the presuppositions of the claim?
Every claim has presuppositions. This is not a bad thing. However, this does not mean that a claim’s presuppositions are unassailable. Suppose we take the claim “there’s no good evidence for God” as meaning no scientific evidence, and suppose we take this claim to imply that, therefore, no one can know that God exists. Is there a presupposition there? Yes, there must be, since no valid form of deductive inference follows from the claim to the implication. So we must supply some other premise, namely something like: “If there is no scientific evidence for something, then there’s no reason to think it is true or is known.” Now the implication follows, but there’s a problem. Why think the proffered presupposition is true? You don’t have to prove it false here. The one offering the argument must give good reasons why she thinks it’s true (presumably, scientific ones that are also non-question-begging).
4. Does the claim meet its own standard?
Many times claims cannot even meet their own standard. In that case, the claim is called self-referentially incoherent. Take the presupposition “if there is no scientific evidence for something, then there’s no reason to think it is true or known.” Let us subject it to its own standard: is there scientific evidence for that claim? It seems not; it doesn’t seem to be the type of claim that can be evaluated by the scientific method. If there is no scientific evidence for the claim, what follows? If we regard the presupposition as true, then it means that there’s no reason to think the presupposition is true or known, which means you have no reason to accept the statement. In fact, if we have no reason to say we know it, then presumably (on most accounts) we cannot say we know it, and (on most accounts) we regard it as false (or at the very least undetermined, and so unhelpful). In that case, if it’s false, it’s false, and if it’s true, it’s false.
5. Are there any good reasons to take the claim as true?
After all this, it’s helpful to try to figure out if there are any good reasons to take the claim as true. Even if something is unambiguous, its implications drawn validly, presuppositions explored and defended, and meets its own standard, it doesn’t follow that one should actually believe it. Now we turn to the evidential standpoint. Take the claim, “There’s no scientific evidence for God.” That’s far from clear. Most Christians will make a crucial mistake here. They will assume a “burden of disproof” as it is called. If you can pull it off, it’s a great strategy, since if you’ve disproven something, then it’s certainly not true. However, it lets the objector off the hook too easily. They must show good reasons to think their claim is true. All you have to do in refraining from belief in those claims is to criticize their arguments for their claim.
Too often, Christians are drawn in to arguments where the unbeliever or skeptic never has to defend her claims. She can simply pass on a one-liner from a meme and watch you try to do all the work. No longer!
 The reason I say “on most accounts” is because, in theory, someone might give an account of some type of foundational beliefs that include this presupposition as a belief that does not need any reasons in order for someone to take it as true. However, this is a route most scientists (and people in general) will not take, and even if it is, it will take a pretty good argument for us to think that the presupposition should be taken to be this kind of basic belief.