In his essay The Doors of Perception, Aldous Huxley compared the human mind to a valve which operates to keep-out the total knowledge of everything which would otherwise flood into us and render us unable to function.
This corresponds to Owen Barfield's category of Original Participation - the primordial state in which the mind of Man is immersed in the totality of being, and which therefore has a potential access to everything - yet in practice this mind is not differentiated from the totality, so it is more a passive thing.
Thus in Original Participation are thoughts are caused, and our thinking is not truly free except in potential.
The modern condition (which can be called the Consciousness Soul) is that the mind is separate from the rest of reality; cut-off from it - the condition of alienation in which we doubt eve our own thoughts, along with the validity of our perceptions, the validity of reason, the existence of anything else - including, eventually, the self itself which seems to depend on our thinking it (a process which, presumably, might cease).
In Final Participation - the future divine destination of Man, currently only partially achieved and only by a few individuals (probably); is one in which the mind is not a valve but a voyager. The mind has been freed by the process culminating in the Consciousness Soul and then becomes a Self-Motivated, Free and exploratory vehicle for active exploration of the totality, by thinking.
In principle, all knowledge is the possible - but only in a linear and sequential and selective fashion, and only when sought and thought.