Jacques Lacan's "Real, Symbolic, and Imaginary" categories come to mind.

Not everything we experience has a material basis (eg: emotions, inner dialogue, expectations, etc) but can be "anchored" in our minds through symbols. Those symbols can become a kind of vocabulary with which we can communicate with the subconscious (dreams, intuitions, what we notice/don't notice, ritual, etc) to change what and how we perceive.

Crowley's and Israel Regardie's approach to this field is worth looking into, even though there may be less esoteric ways to acquire the knowledge they shared.