Siddhopaya and Saddhopaya are two core concepts in Vaishnava theology. Though bhakti and prapatti are enjoined by the scriptures as alternative means to be adopted by a mumukshu, God is the actual direct means (upaya) for it. It is in fact the grace of God that plays a major role in securing moksha. In a correct sense God is the primary cause of moksha for an individual. The Mundaka Upanishad states that Brahman is the causeway for attaining the eternal state (amritasya esa setuh). The Katha Upanishad points out that Paramatman can be attained only by those on whom He confers His grace.

In view of this, God is described as siddhopdya. Siddha means one who has been in existence even prior to the observance of the sadhana and since the ever existing God is Himself the principal cause for attaining Him, He is siddhopdya. If God is the upaya for moksha, where is the need for bhakti yoga and prapatti? Why do we have to undertake them? The answer is that bhakti and prapatti are required to secure the grace of God. The individual souls have been deprived of the enjoyment of the blissful Brahman in the state of moksha due to the beginning-less karma which stands in the way of attaining God. The removal of this obstacle is possible only by the grace of God. Bhakti yoga and Prapatti serve the purpose of winning the grace of God. These are, therefore, described as sadhyopaya, that is, the means to be observed for attaining God.

Sadhya means what is to be accomplished by human effort and sadhyopdya implies that bhakti or prapatti is to be accomplished by individuals in order to earn the grace of God.

It may be mentioned here that there are two kinds of cause: primary (pradhana) and accessory (sahakari). God is the primary cause of salvation in so far as He, through His grace helps an individual in his endeavour to attain moksha. Bhakti and prapatti are the accessory cause for moksha since they serve as the basis for the all-compassionate God to confer His grace and remove the obstacles standing in the way to attain Him. If God were to shower His grace on an individual without any kind of effort on his part He would be open to the criticism of arbitrariness. Hence bhakti and prapatti are enjoined by the Sruti as upayas to invoke the grace of God.