The human reason has its primary action as the search for the truth of existence, whether in the abstract, or in the details of the manifested existence. It can turn its focus on the larger issues of how and why we exist, with no specific attempt to turn this into something useful for day to day life; or it can turn its attention to an attempt to help the individual understand and succeed at various intermediate goals of his life and daily activity. The pure effort of reason may not achieve the complete understanding of the complex truth of existence, particularly because that is beyond the powers assigned to the intellect, but it remains a pure attempt when doing so, as it is not simply trying to assert a specific viewpoint or achieve a specific goal. It is when the reason turns its attention to the needs of life and worldly action, that the various demands of the physical nature, the vital mode of desire, emotional attachment and adherence to specific mental formulations begins to divert the intellect from its purest form of action.
Sri Aurobindo observes: “We have seen that the intellect has a double working, dispassionate and interested, self-centred or subservient to movements not its own. The one is a disinterested pursuit of truth for the sake of Truth and of knowledge for the sake of Knowledge without any ulterior motive, with every consideration put away except the rule of keeping the eye on the object, on the fact under enquiry and finding out its truth, its process, its law. The other is coloured by the passion for practice, the desire to govern life by the truth discovered or the fascination of an idea which we labour to establish as the sovereign law of our life and action. We have seen indeed that this is the superiority of reason over the other faculties of man that it is not confined to a separate absorbed action of its own, but plays upon all the others, discovers their law and truth, makes its discoveries serviceable to them and even in pursuing its own bent and end serves also their ends and arrives at a catholic utility. Man in fact does not live for knowledge alone; life in its widest sense is his principal preoccupation and he seeks knowledge for its utility to life much more than for the pure pleasure of acquiring knowledge. But it is precisely in this putting of knowledge at the service of life that the human intellect falls into that confusion and imperfection which pursues all human action. So long as we pursue knowledge for its own sake, there is nothing to be said; the reason is performing its natural function; it is exercising securely its highest right. In the work of the philosopher, the scientist, the savant labouring to add something to the stock of our ascertainable knowledge, there is as perfect a purity and satisfaction as in that of the poet and artist creating forms of beauty for the aesthetic delight of the race. Whatever individual error and limitation there may be, does not matter; for the collective and progressive knowledge of the race has gained the truth that has been discovered and may be trusted in time to get rid of the error. It is when it tries to apply ideas to life that the human intellect stumbles and finds itself at fault.”
Sri Aurobindo, The Human Cycle: The Psychology of Social Development, Chapter 12, The Office and Limitations of the Reason, pp. 119-120