What is jnana yoga?

Jnana yoga is the last phase of the process toward Self-realization, and the only one to focus on Vedanta (“the knowledge that ends the search for knowledge”). Karma yoga and upasana yoga, on the other hand, are considered preparation for hearing the knowledge imparted during the jnana yoga phase. The idea is that we must first make the mind fit through various practices and disciplines so that the knowledge is able to go in. Where the first two yogas are centered on action, the last phase is focused on knowing. In the spiritual world, there are many yogis who are "doers,” but few who are “knowers.”
In the Bhagavad Gita, Krishna tells Arjuna to “Make no mistake, what I am sharing with you is indeed, a profound secret.” (4.3) Jnana or Self-knowledge is a secret because we are conditioned to believe that we are that which isn’t the Self—namely the body-mind. Self-knowledge is also easily misunderstood because it’s counterintuitive, and sometimes purposely obfuscated by those who wish to use it for egotistical reasons. It’s for this reason that it is said that Self-knowledge is the one secret that even once told, still remains a secret! Jnana yoga is a process; a certain unfolding of the truth that slowly completes the picture regarding the nature of our experience and provides the tools for getting out of samsara.
Vedanta suggests four qualifications for gaining jnana. Sometimes abbreviated as “The Four D’s” they include discrimination (viveka), dispassion (vairagya), discipline (shatka sampatti) and burning desire (mumukshutva).
Discrimination is the ability to tell the difference between that which is true (i.e., the subject; consciousness) and that which is not (i.e., all objects; that which is impermanent and comes and goes).
Dispassion is what is gained through maturity and the understanding that all objects are not real (are of the nature to change; not substantial). Dispassion is also the outcome of karma yoga which teaches non-attachment to the results of one’s actions and cultivating an attitude of gratitude for all that’s given.
Discipline is about having control of the senses and having control of what Vedanta refers to as the “organs of action” used to express oneself in the world (hands, legs, speech, etc.). Discipline is typically developed during the upasana yoga phase and often defined to as the “six kinds of wealth”(shatka sampatti), which include mastery of the mind (shama), mastery of the sense organs (dama), the ability to withdraw from sense objects (uparama), forbearance (titiksha), faith pending verification (shraddha), and concentration of the mind (samadhana).
Lastly, desire means having a burning desire for freedom. As the choice of words suggests, this isn’t just a meek interest in obtaining spiritual freedom. Most people with a burning desire have already tried many different other spiritual practices with only limited success, and Vedanta is their last resort. They are also mature enough know that the world cannot provide real happiness—only the temporary kind—and are seeking something they can rely on for lasting satisfaction.
If you are a seeker, you may already have these qualifications to some degree. But in most cases, they will need to be made stronger before advancing to Self-knowledge. For one who is already qualified, understanding of Vedanta will come easily and learning will be a pleasure. Like running a marathon or swimming a mile—you’re either ready for it or you’re not. One must have fitness and the desire to cross the finish line. Some seekers might even find that they need to re-qualify after hearing Vedanta. They realize that in order to progress in their spiritual journey, they have other areas they still need to work on, for example, karma yoga and gaining a sense of humility.
Jnana yoga is broken out into three stages: shravana, manana, and nidhidyasana. The first, shravana, is listening to the teachings for an undetermined length of time from a qualified teacher who is able to unlock the meaning of the teachings (prakriyas). This may involve putting a temporary hold on our beliefs that we have developed over a lifetime. Vedanta can often sound counter-intuitive because ignorance is hardwired, which is why it’s important to approach it with an open mind.
Manana, the second stage, is the removal of any doubt left over from hearing the teachings and is characterized by a period of question and answer between student and teacher. Manana is marked by much reflection, and clarifying and testing the logic of the teachings.
Lastly, nidhidyasana is the removal of habitual behavior (leftover binding tendencies) and the assimilation of the teachings. In the shravana stage, one would say, “There is the Self.” In the nidhidyasana stage, one would say, “I am the Self” with full conviction. This cognitive shift, from “there is the Self” to “I am the Self,” is that which leads to liberation (moksha). It is also what separates academic study of Vedanta (indirect knowledge) from actual Vedanta as a vehicle for freedom (direct knowledge). But jnana yoga isn’t really about acquiring knowledge but more, the removal of ignorance through a process that includes a process, guidance, repetition and constant discrimination. This is because ignorance is tenacious and just learning Self-knowledge doesn’t guarantee that it will stick. One must still do the work, absorb it and integrate it.
Once Self-knowledge is gained, it’s like a tool chest that we make use of on a daily basis, “planing down the areas made rough.” So, first we must obtain the right tools, and then we must apply them to the task at hand—removal of ignorance. The result is the slow elimination of that which binds us and prevents us from seeing that we are already free.