Sri Aurobindo has described the first cause of impurity in the understanding as stemming from the vital nature and the action of desire. The second cause proceeds from the senses and the sense-mind and their imperfect operation both in terms of perception and in terms of interpretation of the data. Thie third cause of impurity is native to the higher understanding itself and is due to bias, predilection or a predetermined frame of reference used by the higher understanding, which filters the results and skews them.
Sri Aurobindo weighs in on this subject: “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.”
This particular issue is especially difficult for those who have adopted a specific direction or line of thought or understanding, as they tend to see their own framework as being true and others as being less true or even false. We see this particularly in religious and philosophical teachings which try to maintain a wall around the understanding of the seeker who adheres to those specific teachings. Sri Aurobindo asks the seeker to be willing to see and accept truth even in teachings opposed to one’s own direction:
“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 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.”
The goal of the Yoga of knowledge is not to erect a philosophical system that is impervious to being brought down by counter-arguments, but to release the understanding from the bonds of limitation so that it can see and respond to the infinite truth of existence.
Sri Aurobindo, The Synthesis of Yoga, Part Two: The Yoga of Integral Knowledge, Chapter 3, The Purified Understanding, pg. 300
Sri Aurobindo Studies 