Intellectual intuition is even more immediate than sensory intuition, for it is beyond the distinction between subject and object which the latter allows to subsist; it is at once the means of knowledge and the knowledge itself, and in it subject and object are identified. (…) Knowing and being are fundamentally but one and the same thing; they are, so to speak, two inseparable aspects of a single reality, being no longer even really distinguishable in that sphere where all is “without duality” [advaita]. This in itself is enough to show how purposeless are all the various “theories of knowledge” with metaphysical pretensions which occupy such a prominent place in modern Western philosophy, sometimes even going so far, as in the case of Kant for example, as to absorb, or at least to dominate, everything else. The only reason for the existence of such theories arises from an attitude of mind shared by almost all modern philosophers and originating in the Cartesian dualism; this way of thinking consists in artificially opposing knowing and being, an opposition that is the negation of all true metaphysics.
(…) It is necessary to say something at this point about the way in which we use the word “theory”: etymologically, its primary meaning is “contemplation”, and if it is taken thus, it might be said that metaphysics in its entirety, including the realization which it implies, is theory in the fullest sense; but usage has given the word a rather different and above all a much narrower meaning. In the first place, it has become usual to oppose theory and practice, and in its original sense, this antithesis, which meant the opposition of contemplation to action, would still be justifiable here, since metaphysics is essentially beyond the sphere of action, which is the sphere of individual contingencies; but the Western mentality, being turned almost exclusively toward action and being unable to conceive of any realization outside the sphere of action, has come to oppose theory and realization in a general sense.
…In all doctrines that are metaphysically complete, as are those of the East, theory is invariably accompanied or followed by an effective realization, for which it merely provides the necessary basis; no realization can be embarked upon without a sufficient theoretical preparation, but theory is ordained entirely with a view to this realization as the means toward the end, and this point of view is presupposed, or at least is tacitly implied, even in the exterior expression of the doctrine.
René Guénon, General Introduction to the study of Hindu Doctrines.