There are good reasons to argue that knowledge of God --
especially saving knowledge -- is not attainable directly by man. We
are finite; God is infinite. We are fallen and sinful in our minds;
God is perfect. There is a great gulf or barrier between us and God,
that is, if God exists, cares about us, and is good enough to reward
us for seeking God.
In the light of these human limitations, it is reasonable to conclude
that we are totally shut out from knowledge of God, that is, unless
God reveals something of himself to us, and unless God is of such a
nature to do that. But in such a case, there is no question of us
bringing rational deductions or evidence to bear. Knowledge has to
come entirely, as it were, from God's side. Cornelius Van Til's
Calvinist presuppositionalism is sympathetic with this view.