But if you are seeking the absolute truth, then you are presupposing that it can be known.
Not at all.
- One might seek absolute truth because it might be known.
- For the seeker, “absolute truth” can satisfy a more general description for which it is epistemically possible that it not refer to God.
- One needs to be clear about what it means to say that “it can be known.” A Catholic, for instance, adheres to the Church’s dogma that the existence of God can be known through natural reason. The Catholic then believes that it is possible to show that “God exists” is true. That does not exactly imply that absolute truth can be known, if one is (per the doctrine of transcendentals) taking God to be absolute truth, for the Catholic denies that we know God’s essence, even if we know that “God exists” is true.
So, in a very real sense, the truth seeker is presupposing that there is a God’s-eye view of the world - that all truth relations can be theoretically known.
John Haldane has made a similar point. Realism seems to imply that, because truth is independent of
us, it is possible that there should be truths that are in principle unknowable by
us. But the idea of truths that we cannot know is somewhat odd, since truth (on many construals) is a relation between reality and intellect. So it is hard to make sense of the possibility of human-independent truth without the existence of God.
The truth seeker may presuppose that truth is objective. Maybe that is to presuppose that there is “a God’s-eye view of the world.” But that does not imply that he is presupposing the existence of God, since he obviously need not presuppose that under any description derived from God. (And the point Haldane makes is far from trivial.)
However, no circularity seems to ensue, because the supposition that there are human-independent truths should not interfere with the method of inquiry, nor does it assume that God (under any particular conception) exists. This is because the supposition that there are human-independent truths is not something that we are going to establish definitively (unless it is a corollary of God’s existence, which we can establish definitively). The truth seeker could (epistemically) still discover that God does not exist, even if he presupposed that there are human-independent truths. In other words… whether there are human-independent truths is an issue that could only be decided posterior to the question of God. For a similar reason, few people would attempt to argue that (1) relativism is true, and (2) if God exists then relativism is false, so therefore God does not exist.
The naturalist must concede that we can never prove naturalism, not even in theory, because we cannot transcend the natural domain in order to achieve a truly objective perspective.
The negotiation between philosophical systems is always a weighing of various costs and benefits, ie. which views are most intellectually “expensive” to hold. Naturalism can’t be proven. Very little can be proven to a determined skeptic, though. It is epistemically possible that naturalism could be given better support than any other theory, say if we suddenly found that all of our arguments for moderate realism (and other philosophical positions) were actually invalid.