Locke is among very few Western thinkers who confronted the question of revelation directly. Toward the end of his book Locke examines the significance of revelation as a source of knowledge. While considering Divine revelation to be, in principle, a source of certain knowledge, he defines its authority in such a manner that it is assigned a very marginal and subordinate role among the sources of knowledge. To begin with Locke argues that knowledge acquired by human reasoning is more certain that knowledge received through revelation. For while one may doubt the preservation of original revelation through the act of narration, or question the lack of means for validating or substantiating its content, one can always be certain about what his faculty of understanding considers to be true. He therefore concludes that with regard to propositions whose certainty is ascertained by the virtue of having self-evident quality, and hence admitted through immediate intuition, or by the evidence of deductive reasoning through demonstration, revelation is superfluous and not needed.Locke gives revelation the upper hand over reason in two instances. First, in questions belonging to the realm of faith. This realm, being inaccessible to human reasoning, is governed by revelation. Secondly revelation should supersede reason in the realm of probable knowledge which does not rise to the level of certainty. Yet even this conditional recognition of the authority of revelation is not maintained for long, for as Locke proceeds in his discussion of the status of revelation, he manages to undermine whatever is left of its authority; and he does that not by compelling evidence, but through a sheer act of will. As he put it:
There can be no evidence, that any traditional revelation is of divine original, in the words we receive it, and in the sense we understand it, so clear and so certain, as that of the principles of reason: and therefore nothing that is contrary to, and inconsistent with, the clear and self-evident dictates of reason, has a right to be urged or assented to as a matter of faith, wherein reason has nothing to do.
But the concession which Locke gives to revelation in the area of knowledge where reason either has no access or produces uncertain knowledge, are more apparent than real. This is because he perceives revelation to be contra-distinguished to reason, and hence reducible to ungrounded faith. That is to say, by not considering revelation as a source of knowledge capable of endowing reason with information as reality does, revelation is immediately established as a rival body of knowledge at par with the body of knowledge credited as truth by reason. Indeed Locke even rules out the possibility of having self-evident truth embodied in revelation which can be accepted immediately through intuition, thereby contra-distinguishing revelation with intuitive knowledge. Locke writes:
For since no evidence of our faculties, by which we receive such revelations, can exceed, if equal, the certainty of our intuitive knowledge, we can never receive for a truth anything that is directly contrary to our clear and distinct knowledge.
Lock’s contradistinction of reason and revelation becomes especially problematic when we realize that by reason Locke does not simply refer to the formal principles of logic, but also understands a body of knowledge acquired through sensation and reflection. Hence reason signifies, in Locke’s terminology, common-sense knowledge accepted by society. This understanding is quite apparent in the following passage:
For in the cry up of faith, in opposition to reason, we may, I think, in good measure ascribe those absurdities that fill almost all the religions which possess and divide mankind. For men having been principled with an opinion, that they must not consult reason in things of religion, however apparently contradictory to common sense, and the very principles of their knowledge, have let loose their fancies and natural superstitions.
Granted that religiosity has the potential, in the absence of sound methods of derivation, to revert to superstition, one cannot use common sense as the certain of truth. Locke’s attitude toward revelation can only lead to undermining its authority.
Source: The foundation of knowledge, by: Louay Safi