Here’s an interesting quote by William Walker Atkinson:
“Mental Concentration consists of the three following elements, viz, (1) The application of earnest Voluntary Attention upon one particular subject or object; (2) the application of Perception, Observation, Apperception and Thought upon that subject or object, with the determined and definite purpose of extracting from it all possible information concerning its qualities and relations; (3) the restriction and limitation of the field of Attention by means of a determined inhibition or “shutting out” of other sensations, perceptions, and thoughts. This third element, usually ignored in popular thought on the subject of Mental Concentration, is really the characteristic and most essential element involved in the process.
Mental Concentration calls into action the power of the will; for that matter, Voluntary Attention, as its name indicates, is distinctly an act of will. Mental Concentration, as we have said, is merely an intensive form of Voluntary Attention—it is Voluntary Attention, “only a little more so.” In ordinary Voluntary Attention, the will acts so as to direct and hold the Attention upon a particular subject or object; in Mental Concentration, the will manifests itself especially in the coordinate action of keeping out of the field of consciousness other impressions, perceptions, and thoughts. In this dual‑action there is obtained (1) “keeping in mind” the selected subject or object; and (2) “keeping out of the mind” all other subjects or objects. Mental Concentration imposes “a continuity of Attention to the same subject.” But this “continuity of Attention” is by no means fully insured by the mere act of “keeping in mind” the selected subject or object of thought; it requires also the “keeping out of the mind” all disturbing or distracting influences. If the will relaxes its hold upon the Attention, then the latter is quite likely to be attracted to and carried away by some of the countless thoughts, ideas, or notions which constitute the “stream of thought,” and which are brought into consciousness by means of the Law of Association. In order to secure efficient Mental Concentration, the will must be trained to prevent the Attention from being seduced, allured, enticed, decoyed, inveigled, and led astray by attractive “passing thoughts.”
Gordy brings out this idea very clearly in the following passage: “As you use your will to give your attention to geometry, although it attracts you less than a number of other subjects, so if you really study it, you will use your will to prevent your mind from being dragged away from it by the interests that are constantly importuning you. He who possesses this power in a high degree possesses in a high degree the power of Voluntary Attention—to give steadiness to the mind, to prevent it from going capriciously here and there under the influence of the interests that happen to be present at the particular moment.” The Secret of Mental Concentration, then, is seen to consist of the manifestation of its essential characteristic—the added characteristic superimposed upon those of ordinary Voluntary Attention—namely, that of “keeping out,” “shutting out,” or inhibiting the influence of distracting, disturbing, and diverting “outside thought,” or “other ideas.” Voluntary Attention, once directed and held by the will upon a certain object or subject, will readily permit the efficient activity of Perception, Apperception and Thought, provided that by Mental Concentration the “other” or “outside” attractions are “shut out” and “kept out” of consciousness. We ask you to consider carefully, and to fix in your mind, this fact of the importance of the “shutting out” and “keeping out” process. If you will acquire the “knack” of this “keeping out” and “shutting out” process, you will have mastered the art and science of Mental Concentration—for Voluntary Attention will “do the rest” for you.”
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