The solution to the riddle of rebirth and karma lies in understanding of the secret intention that is working itself out through these mechanisms. Sri Aurobindo reviews this intention: “At first she is physical Nature building her firm field according to a base of settled truth and law but determined by a subconscient knowledge she does not yet share with her creatures. Next she is Life growing slowly self-conscious, seeking out knowledge that she may move seeingly in them along her ways and increase at once the complexity and the efficacy of her movements, but developing slowly too the consciousness that knowledge must be pursued for a higher and purer end, for truth, for the satisfaction, as the life expression and as the spiritual self-finding of the soul of knowledge. But, last, it is that soul itself growing in truth and light, growing into the absolute truth of itself which is its perfection, that becomes the law and high end of her energies.”
Each of these stages has a characteristic type of energy that is expressed, and the return for that energy is correlated to that characteristic type. Thus, we see that the law of Karma varies in its expression depending on the type of energy. “At first there is the return of skill and effectual intelligence–and her own need explains sufficiently why she gives the rewards of life not, as the ethical mind in us would have it, to the just, not chiefly to moral good, but to the skilful and to the strong, to will and force and intelligence,–and then, more and more clearly disengaged, the return of enlightenment and the satisfaction of the mind and the soul in the conscious use and wise direction of its powers and capacities and, last of all, the one supreme return, the increase of the soul in light, the satisfaction of is perfection in knowledge, its birth into the highest consciousness and the pure fulfilment of its own innate imperative. It is that growth, a divine birth or spiritual self-exceeding its supreme reward, which for the eastern mind has been always the highest gain,–the growth out of human ignorance into divine self-knowledge.”
We can see in this schema that the confused ideas about the law of Karma prevalent in our normal line of understanding can be disentangled and put into a perspective which reveals a systematic, step-by-step development with the energies of the world precisely responding to the level and intensity of the energy that we expend in the world.
Sri Aurobindo, Rebirth and Karma, Section III, Chapter 16, The Higher Lines of Karma, pg. 154, http://www.lotuspress.com/item.php?item=990117