by Scott F. Aikin and Robert B. Talisse 
Being a responsible believer requires one to have reasons for one’s beliefs. In fact, it seems that having reasons for one’s beliefs is a requirement for seeing them as beliefs at all. Consider the conflict in thought that arises with assertions like the following:
I believe I live in Nebraska, but I have no idea why I believe that.
I hold firmly that there are jellybeans in that dish, but I have no reason for doing so.
I’m confident that it will not rain on the picnic, but I have no evidence for that.
I support a flat-tax system, but all of my information concerning economic matters is highly unreliable.
Statements like these are conflicted because in each the but-clause seems to retract the grounds for asserting what came before. To affirm, for example, that one lives in Nebraska is often to affirm also that that one has reasons that are sufficient to support that claim. Statements of the kind above, then, don’t look like they could be beliefs at all; they rather something else – perhaps a cognitive symptom, an obsession, a queer dogmatism.
We may say that beliefs are supposed to be not only reason-responsive, but reason-reflective. Our beliefs should be based on our evidence and proportioned to the force of our evidence. And so, when we hold beliefs, we take ourselves to be entitled to reason to and from them. So beliefs must be backed by reasons.
Reason-backing has a curious pattern, however. Each belief must be backed by reasons. But those backing reasons must themselves be backed by still further reasons. And so on. It seems, then, that every belief must be supported by a long chain of supporting reasons.
This is a point familiar to anyone who has spent time with children. Why? is a question that can be (and often is) asked indefinitely. The child’s game of incessantly asking why? may not be particularly serious, but it calls attention to the fact that, for every belief you hold, you ought to be able to say why you hold it.
These rough observations give rise to a deep problem, one that has been at the core of the philosophical sub-discipline of epistemology since its inception.