Was the unconscious mind unknown to the prophets and poets of ancient Israel? Or were they aware our awareness had limits? No doubt it would be anachronistic to attribute a modern understanding of the mind to the ancient authors, but I think there’s evidence enough that they knew of dark recesses within themselves.
Consider for instance the words of the Psalmist, who cries, “But who can discern their own errors? Forgive my hidden faults” (Psalm 19:12) and “Search me, God, and know my heart; test me and know my anxious thoughts. See if there is any offensive way in me, and lead me in the way everlasting.” (Psalm 139:23-24)
Though it is sometimes unclear whether the secrets of the “heart” being spoken of refer merely to that which is hidden from others or also to that which is hidden from self, phrases like “Who can discern their own errors?” seems to strongly suggest elements of self deception. As does the reflection of Jeremiah when he says, “The heart is deceitful above all things and beyond cure. Who can understand it?” (Jeremiah 17:9)
Then of course there are figures like Daniel, who unpack dreams that are obscure to the dreamers. “As for me, this mystery has been revealed to me, not because I have greater wisdom than anyone else alive, but so that Your Majesty may know the interpretation and that you may understand what went through your mind.” (Daniel 2:30)
An understanding of hidden depths to the self seemed to carry though into New Testament times also. The apostle Paul writes, “He will bring to light what is hidden in darkness and will expose the motives of the heart” (1 Corinthians 4:5) and “As the secrets of their hearts are laid bare. So they will fall down and worship God” (1 Corinthians 14:25) and “I pray that out of his glorious riches he may strengthen you with power through his Spirit in your inner being”. (Ephesians 3:16)
And yet, it would appear that we are not without their own resources, for the Psalmist also writes, “I have hidden your word in my heart that I might not sin against you.” (Psalm 119:11)
“Scripture is full of the idea of the subconscious. David prays that he may be forgiven for sins of which he is unaware. We say that we are born and conceived in sin-which does not merely refer to the activity of the parents but means that we are sinners when we come into the world even though we are not self-conscious”
– Cornelius Van Til