The cycle of existences (samsara) is regarded as having no beginning, for as every event of the present life is the result of an action done in a past one, the same must hold true of each preceding existence ad infinitum. The subsequent effectiveness of guilt and of merit, commonly called adrishta or "the unseen," but often also simply karma, "deed or work," is believed to regulate not only the life of the individual, but the origin and development of everything in the world; for whatever takes place cannot but affect some creature, and must therefore, by the law of retribution, be due to some previous act of that creature. In other words, the operations of nature are also the results of the good or bad deeds of living beings. There is thus no room for independent divine rule by the side of the power of karma, which governs everything with iron necessity. Hence, even the systems which acknowledge a God can only assign to him the function of guiding the world and the life of creatures in strict accordance with the law of retribution, which even he cannot break. The periodic destruction and renewal of the universe, an application of the theory on a grand scale, forms part of the doctrine of samsara or cycle of existence. Common to all the systems of philosophy, and as old as that of transmigration, is the doctrine of salvation, which puts an end to transmigration. All action is brought about by desire, which, in its turn is based on avidya, a sort of "ignorance," that mistakes the true nature of things, and is the ultimate source of transmigration. Originally having only the negative sense of non-knowledge (a-vidya), the word here came to have the positive sense of "false knowledge." Such ignorance is dispelled by saving knowledge, which, according to every philosophical school of India, consists in some special form of cognition. This universal knowledge, which is not the result of merit, but breaks into life independently, destroys, the subsequent effect of works which would otherwise bear fruit in future existences, and thus puts an end to transmigration. It cannot, however, influence those works the fruit of which has already begun to ripen. Hence, the present life continues from the moment of enlightenment till definite salvation at death, just as the potter's wheel goes on revolving for a time after the completion of the pot. But no merit or demerit results from acts done after enlightenment (or "conversion" as we should say), because all desire for the objects of the world is at an end. The popular beliefs about heavens and hells, gods, demi-gods, and demons, were retained in Buddhism and Jainism, as well as in the orthodox systems. But these higher and more fortunate beings were considered to be also subject to the law of transmigration, and, unless they obtained saving knowledge, to be on a lower level than the man who had obtained such knowledge.