For quite a while now, certainly in the 40 years or so I've been reading about such things, conventional descriptions of mind/brain biology and evolution have suggested that the human mind/brain is really a multi-leveled organ. The organ in our skulls is actually a multi-part brain, with primitive, instinctual elements overlaid with functions that are increasingly evolved and refined.
At the base level of the brain stem is what is sometimes called the "reptilian" brain, a non-thinking brain that responds on a wholly instinctive, preverbal level to basic urges of pain avoidance, pleasure seeking, self-preservation. This faculty is so primitive, we're told, that it doesn't yet even really process sight and sound, but offers nothing but base instinct and emotion. It's the organ that is the source of murderous rage, animal lust, insatiable hunger, terror and fear, blissful pleasure.
Evolved from this is said to be a large, multi-leveled cortex devoted to trafficking sensory input, organizing it, and making rational sense out of all of it. This is what we normally think of as the human brain, and is the source of all thinking and most everything we normally call "mind." The thing we call "thinking" is, by some descriptions, nothing more than a highly complicated system of organizing sensory data.
While we think of this big-lobed, cauliflower-like mass of soft tissue as a lordly object worthy of reverence, many neuroscientists will point out that the thinking brain really does no more than articulate and manage the same base impulses that drive the reptilian brain. Most thinking, most cultural advances, most lofty scientific exploration and thought, after all, is really still about seeking peace and pleasure, avoiding pain and discomfort. This rational brain is, in the final measure, only very slightly more evolved and refined than the reptilian brain that makes us jumps when a loud noise startles us, or recoil in disgust when we see decay.
Much more mysterious, and only now starting to draw some notice, is a mind-brain function that serves a more transcendental role. It is a mind capacity that has been known by mystics over the centuries, but one that has recently been observed and commented on by science, as well. It is a faculty of pure awareness itself, which exists on a level entirely divorced from the push/pull faculty by which we avoid pain, seek pleasure, and scheme to survive as an individual organism. People sometimes imagine that this state is a kind of "observing self", an inner reporter or journalist. But that's not it, either, because with genuine awareness there is no sense of self vs other, no distinction between an observer and objects being observed. There is only utter, non-judgmental immersion in the experience of phenomena. It's as though phenomena is experiencing itself.
I think that even moderately serious meditators have had small tastes of this level of mind. It's a place of serene acceptance of all things as they are, free of all wanting or rejecting. It is entirely devoid of all the fear that fuels virtually all activity attributed to the mind. Time falls away utterly during these revelations, as do all dual concerns of all kinds. Good and evil, life and death, merge into a single taste. There is no longer any need to want or avoid anything at all; you take comfortable refuge is whatever is. Of course, this lovely sensation vanishes almost instantly, in the time it takes us to recognize that it's something unusual. It disappears just as soon as we remember to pick up the familiar blanket of unhappiness, as soon as we remember to separate ourselves from our experience.
Our glimpses of this unique state are maddeningly rare, terribly brief. So fleeting, so unusual, that we convince ourselves that this transcendence, this liberation, is something we must desperately court, something to be achieved through great effort. It is, we believe, a pinnacle to be climbed.
Only gradually do we come to the suspicion that this condition we rarely glimpse is actually the natural, true state of things. It's a treasure lying at our feet, not found at the top of a forbidding pinnacle. We may soon recognize that realizing this transcendence does not require us to do much of anything, only that we give up all the self-induced effort that has prevented us from seeing things as they are.
Like a man who hoards pennies, unaware that he owns a gold mine, we suddenly see that the "mind" we've defined for ourselves is actually the hindrance that has prevented us from seeing the genuine nature of mind all this time. The pain and suffering that dominate human life and govern nearly all of our actions turns out to be the result of delusion; and escaping the cycle of suffering requires nothing more than the courage and despair to see plainly.
Even the first glimpse of this reality changes things for all time. Pain and suffering will return, but now and forever more when they visit, you'll have the quiet, secret understanding that they are clouds formed from illusion and will vanish like smoke when the winds freshen. One must only be patient.