You come up with an idea. And someone asks, "How do you know that's right?"
And what do you say? How do you answer that.
Induction is one of many attempts to answer that question. It's a positive way to know you're right, to build up your idea. You say, "My idea is good because I induced it."
Another tempting answer is, "Because Einstein said so." An appeal to authority is a natural answer to how you know an idea is right. Ultimately that is what the question seeks – some kind of authority, above your judgment, which you can appeal to. By it Einstein or induction, no authority is necessary.
What they want, the motivation behind the question, is a guarantee that'll hold into the future. A defense against the uncertainty of new ideas and new thinking.
The question, "How do you know that's right?" is a bad question. It's inherently bad. It begs for an authoritarian answer. And, worse, it drops the proper context.
(A little like how "Who should rule?" begs for an authoritarian answer, like Karl Popper explains. Questions can be bad and designed to prompt bad answers. Sometimes you have to dispute the question itself.)
A good reply is, "You got a better idea?"
The only context in which it's proper to dispute an idea is if you have an alternative idea, or you see something wrong with the idea (a criticism).
Offer a rival idea, or criticism, or stop complaining. If you can't point out any problem with an idea, and no one knows any alternative, you should be accepting the idea, not raising meaningless, nonsense doubts (which is what "How do you know that's right?" does).
The question, "How do you know that's right?" offers neither a rival nor a criticism. It doesn't provide the appropriate context to defend an idea. An idea can be defended against a criticism. And it can be argued against a rival. But an idea cannot be defended against NOTHING, against arbitrary contextless demands that your idea be better, somehow, and justify itself in a vacuum.
How do I know it's right? Well, how do you know it's wrong?
I'm not omniscient. I don't know it's right in that sense. What I know is it doesn't contradict any of my observations, it doesn't come into conflict with my other knowledge, it's not refuted by any criticism I know of. And what I know is, it's useful, it solves some problem, that's why I made the idea and what it's for.
If an idea solves a problem, and no one knows anything wrong with it (the idea or the problem) or any alternatives, then that's the highest standard of knowledge possible to man (who is fallible and non-omniscient, which is fine, that's not a bad thing). By asking for more, the questioner tries to hold knowledge to an impossible standard. That is a generic tactic he could use to attack any and all knowledge, and is therefore a recipe for complete skepticism. It should be rejected out of hand.
I know it's right – in the fallible, contextual way – because I thought about it. I judged it. I exposed it to criticism, I sought out rivals, I used the methods of reasoning proper to man. I did what I could. What'd you do, Mr. Generic Doubter? These actions I took do not ensure it's right, but they are actually useful things to do, so that's good, not bad.
If you come up with a criticism or an alternative, none of that stuff I did is any protection for my idea. I can't refer to it to win the debate. My idea is on its own, left to its merits, to be judged by its content and nothing else.
What people want to do is set up positive authorities so they can stop worrying about their ideas. They know it's right, so they don't have to fear criticism or alternatives, since they already have the answer. They are trying to close the book on the issue, permanently. They want an out-of-context way to positively support an idea so that it will apply to all future contexts, so they'll never have to think again.
That is what the tradition of positive justification of ideas – the "justification" found in the ubiquitous "knowledge is justified true belief" – is all about. It's about out-of-context authority to preemptively defend against unknown future criticisms and new alternative ideas. It's about setting up an authority for all to bow down to, and ending progress there. So that when rebellious thinkers dare to criticize the status quo, instead of addressing the criticism, they can simply give their generic (contextless) answer to how they know they are right, the same one they've always given, and always will give.
No matter how much support, authority, justification, or positive validation an idea has, that is no defense against criticism. If there is a reason your idea is false, then it's false, too bad about all the authority you made up for it. It's not relevant, it's useless, it shouldn't be part of the discussion, it's just a bunch of nonsense with no functional purpose in a debate. You can never answer a reason your idea is false by saying how much evidence supports it. So what? An idea with a bunch of evidential support can still be false, can't it? No matter how much authority of any kind is behind your idea, it can still be false, can't it? So what good is that authority? What's it for? (Disclaimer: I do not accept that evidential support is a meaningful concept. But I think those that do accept it, also accept that it doesn't guarantee against falseness.)
Do you intend deal with alternative, rival ideas by adding up the positive authority for each and seeing which gets a higher score. That method is terrible. One problem is there's no way to do the scoring objectively. What you should do is point out something wrong with the rival idea – a criticism. If you can't do that, why are you opposing it anyway?