As per Hinduism scriptures karma acts as the hidden spiritual ingredient that facilitates movement of life from one manifestation to another, body after body. In absence of karma life simply could not evolve in cosmic system.
The doctrine of karma can be understood only by one who believes in Hinduism, doctrine of Bhagavad Gita and also spirituality as defined in Hinduism. As per Indian spirituality it is primarily the spirit, soul atman within human body that rules the roost.
After death of human body, the released soul atman manifests another human body based on residual balance of karma at the time of death. Belief in reincarnation, doctrine of life after death and world of souls’ atmans is an absolute must to understand law of karma.
A soul atman in its cosmic sojourn gathers impurities and to cleanse self of dross impurities within starts cosmic life cycle of every soul atman. The cleansing of soul becomes possible only through doctrine of karma and evolution.
For a soul atman to evolve to state of absolute purity it needs passing through a maze of 8.4 million bodies on the whole. The initial 7.3 million manifestations by soul atman occurred in insect, plant and animal form. In the remaining 1.1 million manifestations in human form one is expected to reach state of absolute purity as a soul atman.
If we believe we are a human body manifesting a soul atman, we are ill informed. On the contrary the reverse is true. We are primarily a spirit, a consciousness manifesting human form. To cleanse self of dross impurities within, reach state of absolute purity is the cosmic goal of life for every soul atman.
Cleansing of self becomes possible travelling path of spirituality detailed in Bhagavad Gita. In absence of jnana wisdom contained in Bhagavad Gita, none world over could reach state of absolute purity. State of absolute purity for a soul atman announces the need for human body to indulge in karma ceases to exist.
Our soul atman shall keep manifesting form after another until we reach state of absolute purity. State of self realization, god realization means our karma negating to zero forever.