What Alice Bailey writes in "A Treatise on White Magic" about the Concrete Mind

A Treatise on White Magic

The soul is as yet an unknown quantity. It has no real place in the theories of the academic and scientific investigators. It is unproven and regarded by even the more open-minded of the academicians as a possible hypothesis, but lacking demonstration. It is not accepted as a fact in the consciousness of the race. Only two groups of people accept it as a fact; one is the gullible, undeveloped, childlike person who, brought up on a scripture of the world, and being religiously inclined, accepts the postulates of religion - such as the soul, God and immortality - without questioning. The other is that small but steadily growing band of Knowers of God, and of reality, who know the soul to be a fact in their own experience but are unable to prove its existence satisfactorily to the man who admits only that which the concrete mind can grasp, analyze, criticize and test.

In considering these two ways of ultimate decision let not the man who should use his common sense and take a line of action based upon the use of the concrete mind, practice the higher method of waiting for a door to open.

Another hindrance may be found in the strong development of the concrete mind. I would here impress upon you that this development must in no way be considered a detriment. All has been in due course of evolution, and later when the Orient and the Occident have reached a point of better understanding and interplay their interaction will be of mutual benefit; the East will profit from the mental stimulation afforded by the strong mental vibration of its Western brother, whilst the Occidental will gain much from the abstract reasoning of the Oriental, and, through the effort to grasp that which the first subrace of the Aryan root race so easily apprehended, he will contact his higher mind, and thus build with greater facility the bridge between the higher and the lower mind. The two types need each other, and their effect upon each other tends to eventual synthesis.
The concrete mind, in itself, offers opportunity for a treatise of great length, but here it will suffice to point out a few of the ways in which it hinders those races who so paramountly represent it.

By its intense activity and stimulated action it hinders the downflow of inspiration from on high. It acts as a dark curtain that shuts out the higher illumination. Only through steadiness and a stable restfulness can that illumination percolate, via the higher bodies, to the physical brain and so be available for practical service.
The wisdom of the Triad exists for the use of the personality, but is barred by the disquisitions of the lower mind. When the fire of mind burns too fiercely, it forms a current which counteracts the higher downflow, and forces the lower fire back into seclusion. Only when the three fires meet, through the regulation of the middle fire of mind, can a full light be achieved, and the whole body be full of light, the fire from above - the triadal light - the fire of the lower self, - kundalini - and the fire of mind, - cosmic manas - must meet upon the altar. In their union comes the burning away of all that hinders and the completed emancipation.
By discrimination - a faculty of the concrete mental body - the lower bodies are trained in the art of distinguishing illusion from the center of reality, the real from the unreal, the self from the not-self. Then ensues, consequently, a period that must be surmounted wherein the attention of the Ego is centered necessarily on the lower self and its vehicles, and wherein, therefore, the vibrations of the Triad, the laws that deal with macrocosmic evolution, and the subjugation of fire for the use of the Divine, have temporarily to be in abeyance. When man quickly sees the truth in all that he contacts, and automatically chooses truth or the real, then he learns next the lesson of joyful action, and the path of bliss opens before him. When this is so, the path of occultism becomes possible for him, for the concrete mind has served its purpose, and has become his instrument and not his master, his interpreter and not his hinderer.
The concrete mind hinders in another and more unusual way, and one that is not realized by the student who attempts, at first, to tread the thorny road of occult development. When the concrete mind is rampant, and dominates the entire personality the aspirant cannot cooperate with these other lives and diverse evolutions until love supersedes concrete mind (even though he may, in theory, comprehend the laws that govern the evolution of the Logoic plan and the development of other solar entities besides his own Hierarchy). Mind separates; love attracts. Mind creates a barrier betwixt a man and every suppliant deva. Love breaks down every barrier, and fuses diverse groups in union. Mind repels by a powerful, strong vibration, casting off all that is contacted, as a wheel casts off all that hinders its whirling periphery. Love gathers all to itself, and carries all on with itself, welding separated units into a unified homogeneous whole. Mind repels through its own abundant heat, scorching and burning aught that approaches it. Love soothes and heals by the similarity of its heat to the heat in that which it contacts, and blends its warmth and flame with the warmth and flame of other evolving lives. Finally, mind disrupts and destroys whilst love produces coherence and heals.

He aspires to the occult path and considers changes and events in the light of all preceding events, and the longer and more accurate his memory the more he can dominate all possible situations.
Thus two of the hindrances will be found to be:

The comparative newness and change which is characteristic of the Occident.
The development of the concrete mind.

Our third hindrance grows out of the preceding one.

In secondary principles, which all opposing forces are at present emphasizing, the use of the lower mind involves the danger of criticism, the employment of methods sanctioned by time in the three worlds - methods involving personal attack, invective and the expenditure of force along destructive lines, and a spirit contrary to the law of the plane of unity. The term "opposing forces" is used rightly if you employ it only in a scientific sense and mean the contrasting pole that leads to equilibrium. Remember therefore, that opposing groups may be quite sincere, but the concrete mind acts in them as a barrier to the free play of the higher vision. Their sincerity is great but their point of attainment along some lines less than that of those who adhere to basic principles, seen in the light of the intuition.

Idealism is analogous to the thought that precedes creation. The capacity for abstract thought and for concentration on the ideal is only now in process of development, for this capacity involves the utilization of certain atoms, the employment of matter of the higher subplanes and the ability to synchronize one's vibrations with the Great Ones. Only a few people in the race are true idealists (though their numbers are increasing); the small minority only, employ the concrete mind; while the masses are swayed entirely by the emotions. The time is coming when the intuitional body (the buddhic vehicle) will be organized, utilizing the higher spiritual mind as its medium. When that organization is completed the lower concrete mind will be nothing but a transmitter or an interpreter. Even abstract or concrete thought will be superseded, and we shall have simply the inflow of the intuition, taking form through the medium of the mind stuff. We shall, therefore, have the apprehension of much that is now incomprehensible to our lower plane vision.

The true transmitters from the higher egoic levels to the physical plane proceed in one or other of the following ways:

They write from personal knowledge, and therefore employ their concrete minds at the task of stating this knowledge in terms that will reveal the truth to those that have the eyes to see, and yet will conceal that which is dangerous from the curious and the blind. This is a hard task to accomplish, for the concrete mind expresses the abstract most inadequately and, in the task of embodying the truth in words, much of the true significance is lost.

The pioneers of the human family, the scientists, thinkers and artists constitute the pituitary body. They express the concrete mind but lack that intuitive perception and idealism which would place them (symbolically speaking) in the pineal gland; they are nevertheless brilliant, expressive and investigating. The objective of the Hierarchy (again symbolically speaking) is to make the pineal gland so potent and, therefore, so attractive that the pituitary body of cell lives may be stimulated and thus a close interplay be brought about. This will lead to such potent action that there will be a streaming forth of new cells to the pineal gland and at the same time such a strong reaction set up that the entire body will be affected, resulting in the streaming upward of many stimulated lives to take the places of those who are finding their way into the center of hierarchical endeavor.

The other types of energy which concern the first two main groups with which the aspirant has to deal are related entirely to the form side. The third and succeeding groups are:
3.Astral energy.
4.The energy of the lower concrete mind, of the chitta, the mind-stuff.
5.The energy of the Personality.
6.Planetary energy.
7.Solar energy, or the Life Breath.

Another basis for discouragement is the over-development of the concrete mind, which in its turn makes too great a demand upon the emotional nature, and consequently again upon the physical. Too great a capacity to see all around a subject, too disproportionate a comprehension of the world's need, and too quick an apprehension of the many issues involved in connection with some particular matter produce a violent vibration in the astral body. This leads to a shattering of the physical vehicle, and the result sensed we term discouragement. It is here that a sense of proportion must be cultivated, that the faculty of wise balancing enters, and that mental equilibrium must be achieved. The cure lies in the realization that time, eternity, evolution (call it what you will) brings all things to pass, and that everything does not depend upon individual effort. It is possible for wise souls to hasten the good work, but the end, nevertheless, is sure. If the wise souls are not forthcoming yet the force of evolution brings all things to pass, even if more slowly. Do not forget this, but when discouragement from mental sources settles down upon you, in quietness adjust yourself, and in contemplation sense the ultimate achievement of that great factor, Time.

We are told in the esoteric teaching that all three aspects of Divinity are themselves triple, and hence we can divide the energy of mind as far as humanity is concerned into three aspects also. We have therefore:

The lower concrete mind, called the chitta or mind-stuff in the Yoga Sutras of Patanjali.
The abstract mind; or that aspect of the mind which is related to the world of ideas.
The intuition or pure reason which is for man the highest aspect of the mentality.

For man, therefore, the Universal Mind can best be grasped as it expresses itself through what we call the concrete mind, the abstract mind, and the intuition or pure reason.
The concrete mind is the form building faculty. Thoughts are things. The abstract mind is the pattern building faculty, or the mind which works with the blue prints upon which the forms are modelled. The intuition or pure reason is the faculty which enables man to enter into contact with the Universal Mind and grasp the plan synthetically, to seize upon divine Ideas or isolate some fundamental and pure truth.

Links' page