Both revelation and faith occupy unique positions among the various criteria of truth because of their religious character. Sometimes they are social in nature, as when we speak of revelations to a community or the working of faith in religious groups. Sometimes they are very personal and subjective, for example when a single person claims to receive a revelation or relies upon faith in the quiet moments of life. In all cases, though, the character is very much religious in nature — in terms of the source, the object, and the use.
As a criterion of truth revelation stands very close to intuition — the primary difference is perhaps that whereas intuition comes from a source that is unknown, revelation is supposed to come from a source that is very well known — usually, a god or gods. Another difference is that while an intuition is always personal, a revelation can either be personal (occurring to just a single individual) or public (occurring to a group and shared socially).
Revelation plays a central role in many religions — indeed, because of its religious significance there is an entire classification of religions known as Revealed Religions. Unfortunately for them, the same criticisms of intuition as a criterion of truth also apply to revelation — and then some. For one thing, revelations appear unreliably and are not necessarily available at moments when decisions need to be made.
Another more serious objection, one not applicable to intuition, is the putative source of the revelation. Presumably a revelation comes from a divine source; but even if we assume that such a source exists in the first place, and assuming that it can be or has ever been the source of any revelations (two assumptions we don’t need to grant and which are very questionable) how can we know it is the source of this revelation?
We can’t really, so any belief that is claimed to be true because of its status as revelation really needs to be tested by other criteria of truth. Once again, we find that a so-called revelation may qualify as a potential source of truth, but we can’t rely upon it to differentiate for us ideas that are true and ideas that are false. For that, we must look elsewhere.
In many cases, people look to their faith to validate beliefs and help them discern what is true and right. But is faith actually a criterion of truth or is it more an attitude or way of going about life? Arguably it does serve as criterion of truth because people so often assert that something is true precisely because it is something they have faith in. Sometimes it is even argued that faith is a gift from God in the same way that revelation is, thus making it subject to the same objections as revelation.
When faith is something ascribed solely to the individual, however, we can also object that firm confidence in the truth of a proposition can in no way serve as a test of the truth of that proposition. It might be argued that not every belief needs to be validated through reason and logic; yet that does not automatically leave a space for “faith” to operate. Faith by itself is merely a firm conviction, but a firm conviction without a reason for that conviction is no guide to truth.
