WHAT CAN BE KNOWN ABOUT GOD AS "GOD-TALK" OF THE ONE, HOLY AND IMMORTAL GOD-HEAD???

Augustine writes: "If one thinks one knows God, one doesn't know him at all, what so ever."
John of the Cross says repeatedly in his ASCENT TO MT. CARMEL that his not knowing was his salvation and union with God.
Meister Eichkheart says that the God-Head of the Trinity is unknowable Unknowable, unspoken, fathomless, searchless, emptiness of any sense-cognitive, perception faculties save for Spirit.
Ram Bam treats this as the Way of Revelation of God to Man.
What is then faith and reason? How do you CLEARLY distinguish the two?
Is this all merely all "God-Talk" of Wittgensteinian language games?