How long can this process continue? It's a bit like asking how many licks it takes to get to the Tootsie Roll center of a Tootsie Pop.1 No one is patient enough to find out! But let's talk theory. There are three basic views about what makes a belief justified.
According to the foundationalist view, we will eventually get to one or more basic beliefs which are special because it's inappropriate (in some sense) to ask me why I hold it. Basic beliefs are justified without appeal to supporting beliefs. For example, the belief that I am currently experiencing a warm sensation might be a basic belief. These basic beliefs serve as a foundation to any set of justified beliefs. So:
- Basic beliefs are justified without appeal to supporting beliefs.
- Non-basic beliefs which only need support from basic beliefs and previously justified non-basic beliefs are justified.
A coherentist view of justification doesn't rely on a foundation of basic beliefs with a careful buildup of justified beliefs on top of that. Instead, a belief is justified if — or maybe to the degree that — it fits (i.e. coheres) with all the other beliefs a person holds.
One way to sketch the difference between foundationalism and coherentism is to pay attention to how we go about accusing someone of holding an unjustified belief. Suppose I believe that Tuesdays bring me abysmally bad luck. If you point out that I don't have any reliable basis to draw that conclusion, you are thinking like a foundationalist. If, instead, you point out that some of the best days in my life have been Tuesdays, you are thinking like a coherentist.
This term doesn't show up nearly as often as the other two, but it's worth mentioning to round out the major possibilities. Roughly speaking, infinitism is like foundationalism without basic beliefs. There are no eventual stopping points. Justification is gained along the way down, instead of put on complete hold until it turns out a belief ultimately relies only on basic beliefs.
Justification and Truth
Holding a true belief is not the same thing as being justified in holding a belief. Justification is more about having a good reason to believe something. It's possible to believe something for a bad reason, but happen to be correct (unjustified true belief). If you agree it's also possible to believe something for a good reason, but happen to be incorrect, then justified false belief is an option.
Still, there wouldn't be much point in worrying about justification if justified beliefs weren't at least more likely to be true than unjustified beliefs.
Why do I bring this up? Because I don't want people to discount coherentism and infinitism out of hand just because it's more obvious that beliefs considered 'justified' under those views could possibly still be false. That's not a fatal criticism. Personally, I think foundationalism turns out to be problematic despite its initial appeal, but this is just a quick introduction to the terms. They'll come up again in future posts.