How unconscious is subliminal perception?

Ever since the concept of the “unconscious” defragmented one of the last nuclei of certitude in the western world, one of the great mysteries that common knowledge has come to associate with psychology is the idea that much of what goes on in our lives occurs outside of awareness. In other words, what we experience is but the tip of the iceberg: massive amounts of information are processed, have an influence on our behaviour, all the while going unnoticed. But is this the case? It seems indeed that we are not always able to retrace the associative causal chains that lead to a thought or action (though the degree to which this is the case is still being debated) - but according to the way we consciously experience the world, it seems to be both immediate and complete to us. Apart from the fact that we may not be able to perceive the entirety of the external world due to information processing limitations inherent to our physical system, what seems more unsettling is that we may not even be able to experience all that we perceive! Is there some limitation of our own internal system that keeps not only the world, but the way this world is represented in us fundamentally unknowable to ourselves?