For as long as humans have history there has existed the belief that
some men can awaken to a wider awareness of the world,
and gain an extraordinary deeper understanding of life,
which has persistently been painted with metaphysical, mysterious connotations,
(s.c. that such a thing is a gift of the gods, or a result of secret rituals, or sacred drugs, and so on),
but there is also a quite non mystical, physiological explanation for this
which can offer those with a personal, passionate interest in the matter
not simply a new theory, but a different practical approach to its actual application.
 

The brain’s operations are, from man’s self based perspective, of two distinct modes:
the conscious (thoughts) and the non conscious (all of its other functions) and you do not have to be a neurologist nor have a detailed knowledge of anatomy to follow this;
just picture it like this (which,  although simplified, is physiologically sound):
there is a line drawn through your head (about eye level) and above it lies the cortex which is the source of all thoughts (sometimes referred to as the new brain),
and below the line is the brain stem (often called the old brain) wherein the basic
functions necessary for life are controlled (breathing, heart rate & blood pressure, inter alia) which is done automatically, in silence and outside of consciousness;
twenty-four hours a day this non conscious part of the brain monitors information constantly passing through it from the rest of the nervous system  --  in contrast,
the conscious part of the brain never monitors what passes through it,
the exception being when the non conscious area calls on it for survival related assistance via its ability to analyze situations with which the old brain is not equipped to deal via its purely automatic responses,
a situation that, when it occurs, is completely beyond the control of consciousness,
and is but another survival instinct.
But apart from this circumstance
(which is apart from any rational interest in expanding one’s understanding),
the conscious part of man’s brain never monitors, nor takes the measure of
the information constantly passing through it concerning things intangible --
affairs from the inner reality, the product of its own creation, or put another way:
consciousness is not conscious of itself,
and specifically not of its stand-alone activities.
From this perspective, the whole idea of awakening to a new sense of reality,
or becoming enlightened to the true nature of things, amounts to this:
it is the attempt to make the conscious part of the brain monitor the information passing through it, same as does the non conscious part, its information;
when this completely unnatural event does occur in a person,
it is what has been so long called: a man’s enlightenment  --   his awakening,
but what takes place is not supernatural, spiritual, or in any way, other-worldly –
what  happens is that the conscious part of the person’s brain suddenly --
for the first time  --   monitors what was going on in it  –
and the result to the person  --   is always astounding  --  there is nothing else to call it.
 

Beyond their understanding, all of the methods, tools & tricks that have been employed by men to achieve a new, extraordinarily insightful state of consciousness
are unrealized efforts to make the conscious part of the brain monitor itself,
and take the measure of the “information” being constantly fed through it  --   something for which it demonstratively is not normally suited, nor apparently
intended to do.
But if, in a person who has in some way been struggling toward this end,
it ever does occur, what it suddenly realizes is (what description would you prefer): mind-blowing!  --   breath-taking!  --  indescribable!  --  unbelievable!  --  they all fit,
while yet none beginning to adequately cover it.

If a man for some reason is born with an instinctive taste for this activity,
and somehow recognizes it as soon as he first hears of it,
and some way eventually manages to make personal, practical sense of it,
understanding it to be entirely an affair of the brain,
then what has been above noted is a possibility --
and is the only thing that will ever satisfy such a person  --  the only thing,
and the clearer picture you have of what it actually is,
the more likely your achieving it.