Yoga does not yield truth because it ignores the objective world.+

Manduka Upanishad:~ Yoga is in the sphere of duality and is unnecessary to one who knows non-duality.

Yoga does not yield truth because it ignores the objective world. Say that yoga has its place rather than its value and that its value is for a certain type of mindset. One cannot live without the physical world; it is the basis of his life, so it must be the starting point of his inquiry. Things, not imaginations, must be the seeker’s material.

Yogi shuts his eyes against the world and then has the temerity to declare that he knows the world to be Brahman! Because he has not inquired into it, he knows nothing.

Yoga helps the yogi by giving him the feeling that the world, which confronts him is not worth bothering about, it detaches him from the world; it makes him treat the world as a dream, i.e. an idea. It does the same to his ego to some extent, because he becomes indifferent to what happens to him. But the great secret is that this is only feeling, he feels these things only but does not know that the world is an idea. Such knowledge can come only after deeper Self-search and in no other way. That is why yogi cannot be Gnani.

Sage Sankara says: - Yoga is not the means of liberation (page 132-133 - Commentary on Brihadaranyakopanishad.

Yoga can yield only duality because everything that one can do or practice becomes a vanishing 'known.' It yields relative truth based on imagination, which is true from a physical viewpoint of view, not non-dual truth, which is the ultimate reality.

It is the difference between feeling and knowledge. The feeling of the yogi that the world is unreal may change in the future because all emotions are liable to change; and the fact is that yogis do change, as when they indulge in accumulating wealth they lose their sense of world unreality though previously they felt it.

A permanent view of the world as unreal can come only after Soulcentric reasoning; such knowledge cannot change. Were the yogi of sufficiently sharp intellect he could discover the ideality of the world by Soulcentric reasoning alone and then it would not be necessary for him to have gone through yoga practice at all; that is why the yoga is for dull or middling intellects.

Panchadesi: - the impossibility of yoga arrives at a successful end to its practices. (P.509 v, 109)

To realize the truth of the whole, one must know the world, that confronts him, otherwise he gets a half-truth. The seeker of truth should not run away from the external world means incapacity to think. Thus, it is necessary to know the nature of the world in which he exists.

The ultimate truth is attainable by perfect understanding, assimilation, and realization of ‘what is what’. The perfect understanding of ‘what is what’ leads to Advaitic ‘Self-awareness. : ~ Santthosh Kumaar