Of all the points of difference between Yoga and Sāṃkhya the admission of Īśvara by the former and the emphasis given by it to the Yoga practice are the most important in distinguishing it from the latter. It seems probable that Īśvara was traditionally believed in the Yoga school to be a protector of the Yogins proceeding in their arduous course of complete self-control and absorptive concentration. The chances of a person adopting the course of Yoga practice for the attainment of success in this field does not depend only on the exertions of the Yogin, but upon the concurrence of many convenient circumstances such as physical fitness, freedom from illnesses and other obstacles. Faith in the patronage of God in favour of honest workers and believers served to pacify their minds and fill them with the cheerful hope and confidence which were so necessary for the success of Yoga practice. The metaphysical functions which are ascribed to Īśvara seem to be later additions for the sake of rendering his position more in harmony with the system. Mere faith in Īśvara for the practical benefit of the Yogins is thus interpreted by a reference to his superintendence of the development of cosmic evolution. Sāṃkhya relied largely on philosophical thinking leading to proper discrimination as to the difference between prakrti and purusha which is the stage immediately antecedent to emancipation. There being thus no practical need for the admission of Īśvara, the theoretical need was also ignored and it was held that the inherent teleological purpose (_purushārthatā_) of prakṛti was sufficient to explain all the stages of cosmic evolution as well as its final separation from the purushas.