What the Bhagavad Gita says about knowledge
The Gita separates knowledge into grades, and the middle one is the trap. 18.21 describes knowledge that sees only separate things, each apart from the others. Nothing in it is factually wrong. It is the knowledge of somebody who has done the reading, and it can tell you everything about how people differ and nothing about what connects them.
18.20 defines the clear kind as seeing one undivided reality in everything that lives, undivided among the divided. The division is granted. Something undivided is also there. That balance matters, because the flattening version, which says differences are illusions, is not wisdom but a way of not listening.
4.38 adds the claim that makes the rest usable: nothing purer than knowledge exists here, and in time a person finds it within himself. It is not imported. And 14.6 supplies the warning, that clarity binds too, by attachment to knowing. The grip of being somebody who understands is the subtlest binding in the book.
The verses 19
4.33
Better than any offering made of things is the offering of knowing, Arjuna.
4.34
Learn it by going and bowing, by asking properly, by being of use.
4.37
As a fire well lit turns firewood to ash, Arjuna, the fire of knowing turns every action to ash in the same way.
4.38
There is nothing in this world as clean as knowing.
4.39
The one who trusts it gets it - devoted to it, with the senses in hand.
5.15
The all-pervading takes on no one's wrongdoing, and no one's good deed either.
5.16
But for those whose not-knowing has been destroyed by knowing the self, their knowing lights up that highest thing, the way the sun does.
7.2
I shall tell you this knowledge in full, together with the living realisation of it.
9.1
Krishna said: To you, who do not sneer at it, I shall tell this most secret thing - knowledge together with the realising of it, knowing which you will be free of what is unlovely.
9.2
This is the king of knowledge, the king of secrets, the purest, the highest.
10.11
Out of compassion for them alone, standing within their own being, I destroy the darkness born of not knowing, with the shining lamp of knowledge.
13.11
… unbroken devotion to me, joined to nothing else; a liking for quiet places; no taste for crowds of people…
13.12
… constancy in the knowledge of the self, and keeping in view what the knowledge of truth is for.
13.18
It is the light of lights, said to be beyond darkness.
14.1
Krishna said: I will tell you again the highest knowledge, the best of all knowing - knowing which, all the sages went from here to the highest completion.
18.20
The knowledge by which you see one unchanging being in everything that lives, undivided among the divided: know that knowledge as clear.
18.21
But the knowledge that sees only separate things of many kinds, each one apart, in all that lives: know that knowledge as driven.
18.22
And the knowledge that clings to one single thing as though it were the whole, with no reason behind it, missing what is actually the case, and narrow: that is called dark.
18.70
And whoever studies this conversation of ours, which is about what is right, will have worshipped me with the offering of knowledge.