This claim is quite meaningless without concrete examples.
Read the Bible, Listen to any sermon or religious debate and you have it. Belivers claim to "know" the mind of God when it suits them and claim divine enigma when it suits them too, conveniently. The Bible is full of such man-made examples. You did it yourself right on this thread when you asked how much of God's mind can we know without actually committing yourself to saying how much of it you allegedly know. Of course, in all such claims, evidence is lacking, so it's your word, nothing more. Which brings up the question: why should I believe you?