I interpret stuff like Billy Graham's saying God isn't detectable as attempts to make things more attractive to the atheist crowd. I didn't think you were involved in anything like that, for sure. I had heard the man drifted into some less-than-sound ideas as he got older, but I never really investigated.

"If God can be fully proved by the human mind, then He is no greater than the mind that proves Him." That's a worthless statement at best. At face value, it's flat-out untrue and misleading. The typical Christian might not pay much attention, it being Billy Graham and all, but the untruth would quickly catch the ear of an atheist. They're always denying that God can be known.

It may also be he isn't the first to say it. Perhaps it struck him as an attractive-sounding sentence and he merely repeated it. I don't really know. What I do know is that it's nonsense. It isn't true of anything whatsoever. One need not fully understand every aspect of anything you can name in order to prove that it exists, neither are any aspects of any things limited by anyone's understanding. The limits of understanding are the limits of understanding; they have no bearing on being.

Now those who claim reality is dependent upon perception, they believe otherwise. Their beliefs are a self-contradictory mess, and we see them asserted fairly frequently. They form the basis of both quantum philosophy and Einsteinian relativity; both fully incorporate the assumption that reality is perception-dependent. Naturally, proponents are not usually very open about their assumptions lest their folly become too obvious and people begin to doubt the authority of "the experts".