Sadhguru explains that gnana yoga is not a philosophy, but a process to sharpen the intellect to a point where it can "penetrate through the process of life and show you what is true and what is not true."
Sadhguru: Gnana does not mean to philosophize, gnana means “to know.” Unfortunately, philosophy is mostly passing off as gnana yoga today. Fundamentally, if you want to pursue gnana, you need a very alert, sharp intellect. Every day and every moment you must slowly sharpen your intellect to a point where it is like razor sharp. It misses nothing. It can go through anything, but nothing sticks to it, it is not influenced by anything that is happening around. This is gnana.
If you can keep your intellect like that, it will naturally penetrate through the process of life and show you what is true and what is not true, what is real and what is not real. But today, people have just jumped to conclusions. They have made philosophies. People openly talk, “Everything is maya. It is all illusion, so why worry?” They are just trying to console themselves. But when maya gets them properly, all their philosophies will evaporate.
It happened to a philosopher: he was going about with great strength, “Everything is maya, don't bother about anything. The whole world that you experience is all illusion.” Once it so happened, he was walking with two of his monks. A rabid monkey which had gone crazy started chasing him in full fury. The philosopher just screamed and ran. After a while the monkey found some other attraction and went away.
The philosopher stopped and realized that all this “maya teaching” suddenly fell down. “Monkey is also maya, monkey's madness is also maya. Monkey is going to bite me, that is also maya. Why did I run like this?” It just hit him so strong. From then on, he was never the same man again.
So talking about the illusory nature of the world, or talking about the Creation and Creator, or believing that the world is like this or that, is not gnana. Gnana yogis cannot afford to believe or identify themselves with anything. The moment they do, the sharpness and effectiveness of the intellect is over. Unfortunately, today in the name of gnana, people just believe so many things – “I am atman, I am paramatman.” They believe in how the arrangement of the cosmos is, the shape and size of the soul, how it will transcend; they read all this in books. This is not gnana yoga, because you are just believing something. People who walk the path of gnana are people whose intellect is such that they are not willing to believe anything, nor do they disbelieve anything. “What I know, I know. What I do not know, I do not know.” This is gnana.