Path of Karma Yoga :
Karma cannot give Moksha, only self knowledge can give Moksha.
1. Moksha delivered by Karma’s will not be permanent
Means one have to again return to this earth for rebirth, because actions give results within time and space. Their results has to end someday, so if Liberation is achieved by Karma’s it will also end some day.
There are many examples in scriptures when people have attained various Loka’s by their actions, but when results diminishes they were again thrown back to earth for rebirth.
2. Liberation will not be absolute
The result will not absolute, that means it has depend on the time and space to give results. Since it become dependent on time and space, so it is a become relative Moksha and not absolute. It will be limited ‘Saguna’ Moksha, may be enjoyed with body. ( Not without body )
3. Which Karma’s will lead to liberation ?
Does one single action or many cumulative actions will give result as liberation? If one believe that one action will give liberation than other actions go useless, or if many cumulative actions will give liberation than it contradict Vedas, as each action has different result.
4. Karma’s already have motive associated with them, so how can they give Moksha?
The ‘daily actions’ which are done to cut off past accumulated results or the wishful actions to attain heaven, how can they both deliver Moksha? So we have to invent a new type of karma which should only deliver the Moksha.
Path of Gyan Yoga :
Gyan Yoga ( or Vedanta ) Moksha is said to be attained by Self Knowledge, by knowing this Atman as real and identifying this physical body as non real. Physical body is changed in each rebirth, but Atman never changed
Adi Sanakara has mentioned that Liberation can only be achieved by knowing the Atman, and understanding the physical body as not real.
In VivekChudamani, Adi Sankaracharya had said :
न योगेन न सांख्येन कर्मणा नो न विध्या । ब्रह्मात्मैकत्वबोधेन मोक्षः सिद्ध्यति नान्यथा ।।
“Moksha cannot be achieved by Yoga, not by Sankhya , not by Karmas, not by any worldly knowledge. Moksha can only achieved by understanding the oneness of Brahman and Jiva, and not by any other means”
Adi Sankara has also highlighted that the problem is seeing the physical body as true, though body is seen due to ignorance caused by Maya.
“For him who has been stung by the serpent of ignorance, the only remedy is the knowledge of Brahman. Of what use are the Vedas and the scriptures, mantras and medicines to such a victim of poison?”