By the understanding we mean that which at once perceives, judges and discriminates, the true reason of the human being not subservient to the senses, to desire or to the blind force of habit, but working in its own right for mastery, for knowledge. <ref>http://incarnateword.in/cwsa/23/the-purified-understanding#p5</ref>
'''''=== Causes of Impurity in Understanding'''''===
* ''Intermiscence of Desire '' - The first cause of impurity in the understanding is the intermiscence of desire in the thinking functions, and desire itself is an impurity of the Will involved in the vital and emotional parts of our being. When the vital and emotional desires interfere with the pure will-to-know, the thought-function becomes subservient to them, pursues ends other than those proper to itself and its perceptions are clogged and deranged. The understanding must lift itself beyond the siege of desire and emotion and, in order that it may have perfect immunity, it must get the vital parts and the emotions themselves purified.
The will to enjoy is proper to the vital being but not the choice or the reaching after the enjoyment which must be determined and acquired by higher functions; therefore the vital being must be trained to accept whatever gain or enjoyment comes to it in the right functioning of the life in obedience to the working of the divine Will and to rid itself of craving and attachment.
Similarly the heart must be freed from subjection to the cravings of the life principle and the senses and thus rid itself of the false emotions of fear, wrath, hatred, lust, etc. which constitute the chief impurity of the heart. The will to love is proper to the heart, but here also the choice and reaching after love have to be foregone or tranquillised and the heart taught to love with depth and intensity indeed, but with a calm depth and a settled and equal, not a troubled and disordered intensity.
The tranquillisation and mastery (sama and dama) of these members is a first condition for the immunity of the understanding from error, ignorance and perversion. <ref>http://incarnateword.in/cwsa/23/the-purified-understanding#p9</ref>
* ''Intermiscence of the Sense-mind '' - The second cause of impurity in the understanding is the illusion of the senses and the intermiscence of the sense-mind in the thinking functions. No knowledge can be true knowledge which subjects itself to the senses or uses them otherwise than as first indices whose data have constantly to be corrected and overpassed. …the beginning of philosophy is the examination of the principles of things which the senses mistranslate to us; the beginning of spiritual knowledge is the refusal to accept the limitations of the sense-life or to take the visible and sensible as anything more than phenomenon of the Reality. <ref>http://incarnateword.in/cwsa/23/the-purified-understanding#p10</ref>
Equally must the sense-mind be stilled and taught to leave the function of thought to the mind that judges and understands. When the understanding in us stands back from the action of the sense-mind and repels its intermiscence, the latter detaches itself from the understanding and can be watched in its separate action. It then reveals itself as a constantly swirling and eddying undercurrent of habitual concepts, associations, perceptions, desires without any real sequence, order or principle of light. It is a constant repetition in a circle unintelligent and unfruitful.
There is nothing to be done with this fickle, restless, violent and disturbing factor but to get rid of it whether by detaching it and then reducing it to stillness or by
giving a concentration and singleness to the thought by which it will of itself reject this alien and confusing element. <ref>http://incarnateword.in/cwsa/23/the-purified-
understanding#p11</ref>
* ''Improper Action of the will Will to know Know'' - A third cause of impurity has its source in the understanding itself and consists in an improper action of the will to know. That will is proper to the understanding, but here again choice and unequal reaching after knowledge clog and distort. They lead to a partiality and attachment which makes the intellect cling to certain ideas and opinions with a more or less obstinate will to ignore the truth in other ideas and opinions, cling to certain fragments of a truth and shy against the admission of other parts which are yet necessary to its fullness, cling to certain predilections of knowledge and repel all knowledge that does not agree with the personal temperament of thought which has been acquired by the past of the thinker.
The remedy lies in a perfect equality of the mind, in the cultivation of an entire intellectual rectitude and in the perfection of mental disinterestedness. The purified understanding as it will not lend itself to any desire or craving, so will not lend itself either to any predilection or distaste for any particular idea or
truth, and will refuse to be attached even to those ideas of which it is the most certain or to lay on them such an undue stress as is likely to disturb the balance of
truth and depreciate the values of other elements of a complete and perfect knowledge. <ref>http://incarnateword.in/cwsa/23/the-purified-understanding#p12</ref>
An understanding thus purified would be a perfectly flexible, entire and faultless instrument of intellectual thought and being free from the inferior sources of
obstruction and distortion would be capable of as true and complete a perception of the truths of the Self and the universe as the intellect can attain. <ref>http://incarnateword.in/cwsa/23/the-purified-understanding#p13</ref>