1. Moksha delivered by Karma’s will not be permanent – that means, one have to again return to this 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 liberation and not absolute. It will be limited ‘Saguna’ Liberation, 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 liberation ? – The ‘daily actions’ which are done to cut off past accumulated results or the wishful actions to attain heaven, how can they both deliver liberation ? So we have to invent a new type of karma which should only deliver the Liberation.
According to Gyan Yoga ( or Vedanta ) liberation can be attained by Self Knowledge, by knowing this Atman as real and identifying this physical body as non real. This physical body is changed in each rebirth, but Atman never changes.
न योगेन न सांख्येन कर्मणा नो न विध्या । ब्रह्मात्मैकत्वबोधेन मोक्षः सिद्ध्यति नान्यथा ।।