Question Is there a way to confirm a premises truth? When I looked it up I found two ways suggested. The first was the idea that a premise can be common sense, which I can't compartmentalize from the idea that appeals to consensus are considered a fallacy. The second was that it can be supported by inductive evidence, which to my knowledge can only be used to support claims of likelihood, not certainty.

Accepted:
March 28, 2017

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The answer will vary with the

The answer will vary with the sort of premise. For example: we confirm the truth of a mathematical claim in a very different way than we confirm the truth of a claim about the weather. Some things can be confirmed by straightforward observation (there's a computer in front of me). Some can be confirmed by calculation (for example, that 479x368=176,272). Depending on our purposes and the degree of certainty we need, some can be confirmed simply by looking things up. (That's how I know that Ludwig Wittgenstein was born in 1889.) Some call for more extensive investigation, possibly including the methods and techniques of some scientific discipline. The list goes on. It even includes things like appeal to consensus, when the consensus is of people who have relevant expertise. I'm not a climate scientist. I believe that humans are contributing to climate change because the consensus among experts is that it's true. But the word "expert" matters there. The fast that a group of my friends happen to think that something is true may not give me much reason at all to believe as they do.

We may want to pause over the word "confirm." If by "confirm," you mean "establish with certainty," we usually can't do that. If something isn't just a matter of meaning, math or logic, there's room to be wrong no matter how careful we are. Still, in many cases, there's not much room. Is it possible in some abstract sense of "possible" that Obama wasn't President in 2010? Yes. Is there room for a reasonable person to think he wasn't? Hard to see how.

This point bears on your question about "induction." Outside of math, logic, and meaning, what we know we know by experience---direct or indirect, ours or someone else's. In those cases, there's always room for doubt, and what we believe is more or less likely. There's no way around that; it's almost always possible that one or more of the premises of our arguments might be false. That's the price we pay for having knowledge about the world itself and not just, to use Hume's phrase, relations among ideas.

Summing up: there are lots of ways to confirm things, but which way is best depends on what we're trying to confirm. In most cases, "confirm" doesn't amount to "become certain." There are fallacious ways to argue for a premise, but reasonable ways of confirming one's beliefs---consulting experts, for example---may be superficially like fallacious ways (asking a casual sample of my friends, for instance, when the subject is one they have no special knowledge about). There's no simple rulebook for knowledge, even though there's a great deal that we actually know.