A detailed analysis of the mental capacities shows that there are different functional levels. Without delving too deeply into these distinctions at this time, it is sufficient to recognise that there is a sense-mind that essentially captures the impressions of the senses and reacts to them, and there is a higher mind of reason, intelligence and understanding that can process abstract concepts and do so in a manner that is separate from the sense-mind’s habitual and limited patterns. Western science in fact confirms this when it analyzes regions of the brain and assigns different functions to those different regions, with the frontal cortex identified as the region of abstract and higher reasoning, and other sections, such as the hippocampus, representing more basic processing functions. The Yogis of India developed a very detailed psychology of the mind and used the term “buddhi” for the higher understanding mind that was able to distance itself from the habitual patterns of action and reaction of the basic sense-mind.
Sri Aurobindo observes: “…we exclude from it the action of the sense mind which merely consists of the recording of perceptions of all kinds without distinction whether they be right or wrong, true or mere illusory phenomena, penetrating or superficial. We exclude that mass of confused conception which is merely a rendering of these perceptions and is equally void of the higher principle of judgment and discrimination. Nor can we include that constant leaping current of habitual thought which does duty for understanding in the mind of the average unthinking man, but is only a constant repetition of habitual associations, desires, prejudices, prejudgments, received or inherited preferences, even though it may constantly enrich itself by a fresh stock of concepts streaming in from the environment and admitted without challenge of the sovereign discriminating reason. Undoubtedly this is a sort of understanding which has been very useful in the development of man from the animal; but it is only one remove above the animal mind; it is a half-animal reason subservient to habit, to desire and the senses and is of no avail in the search whether for scientific or philosophical or spiritual knowledge. We have to go beyond it; its purification can only be effected either by dismissing or silencing it altogether or by transmuting it into the true understanding.”
Sri Aurobindo, The Synthesis of Yoga, Part Two: The Yoga of Integral Knowledge, Chapter 3, The Purified Understanding, pg. 295-296