In spite of the far-reaching influence of relativism (that is, the idea that there is no absolute truth), most people are not all-out relativists. My previous essays on truth should demonstrate why. To abandon the absoluteness of truth is to abandon all logic and reason, and even one’s own observation and thinking processes. And most people simply cannot bring themselves to jump off the edge of reason into the seas of insanity. Truth’s absoluteness is at least as necessary as existence itself.
Yet there is another view of truth that many hold; namely, that truth is unknowable. We’ll call this view unknowablism. According to this view, truth may be absolute, but there’s no way of knowing what the truth is – of knowing how to discriminate correctly between two conflicting propositions.
This view definitely sounds more responsible; after all, it allows for the fundamental reasoning principle of absolute truth. But ultimately, it is just is irrational as relativism.

Relativism claims that there is no absolute truth. But such a claim is an absolute statement, and therefore self-refuting.
Unknowablism claims that there is no knowable truth. But such a claim is a knowledge statement, and therefore is also self-refuting.

Let me state it another way:
Should someone say, “There’s no absolute truth,” one can reply, “Are you absolute about that?”
Should someone say, “There’s no knowable truth,” one can reply, “Do you know that?”
In other words, one who holds to unknowablism cannot logically be certain about anything, including his own existence. This is no better than relativism; furthermore, I’m convinced that it’s a mere variation of it.

It is logically impossible to know that truth is unknowable.
And remember, we've already determined that relativism is an impossibility; that's a knowable truth right there. We must conclude, then, that there are at least some knowable truths . . . and that’s a good place to start.