Reliabilism is a form of epistemic externalism that generally states that a belief is justified when it results from a reliable belief forming process that is either doxastically dependent or doxastically independent. That is, S knows that p iff p is true, SBp is true, and S has a reliable process for arriving at p.  In this way, SJp (att) iff (1) it is not in other epistemic evaluative terms, (2) explains how SJp is justified is a function of SBp’s genesis. This principle emphasizes the virtue of the belief forming mechanism and the veridical historicity of the belief over the truth value in order to account for the possibility of a false belief.

Suppose that I claim knowledge of my age, 24. I believe that my age of 24 is true. The process I possess to justify my age is to check my birth certificate. As a notarized document of the government, I believe the process of checking my birth date to its data yields reliable knowledge. I justify this belief forming process from the fact that everyone verifies their age in this way and it is most accurate and consistent. Additionally, I believe the government would not falsify this data as a notarized document. This is an exemplary example of reliabilism because my knowledge is based on the virtue of the belief forming process, naming checking the birth certificate, that is historically reliable and still allows for the possibility of falsity if say, my birth certificate was lost, or doctored, and I forgot my real birth date.