Depending on the mystic, some will say God, some will say the Devil, some will say it's just your subconscious mind trying to burst through.
William Blake was such a man -- artist, poet, mystic, eccentric. He wrote the hymn Jerusalem that was featured in Chariots of Fire but he produced many compelling paintings. Where did HIS inspiration come from?
A sad indictment, Mr B. )
Surely there have to be other reasons for inspiration.