O GOD, who by the leading of a star didst manifest thy only-begotten Son to the Gentiles: Mercifully grant, that we, which know thee now by faith, may after this life have the fruition of thy glorious Godhead; through Jesus Christ our Lord. Amen.
To know by faith is somewhat of a strange idea to many people these days and can lead us into all manner of tricky philosophies. Philosophy is largely fashionable and our understandings of what we can know and what is really there are never still. In fact, what we do in fact know is very nearly nothing. This is because we ourselves are very nearly nothing.
Yet, the letter to the Hebrews tells us that, "faith is the substance of things hoped for , the evidence of things not seen." Human knowledge seems to be dependent on things that can be experienced with the senses, so, if things cannot be directly experienced then doubt can be thrown upon their existence.
God Himself provides the testimony for His existence through His self-revelation. His Epiphany is precisely the medium by which that evidence of things not seen can be conveyed. We are given the opportunity to trust that which can be trusted. We cannot have rock-hard definitive knowledge of God, so we are given a covenant with Him. Faith, hope and love all endure, yet
Faith will vanish into sight;
Hope be emptied in delight;
Love in heaven will shine more bright;
Therefore, give us Love. (Bishop Christopher Wordsworth)