Siddhopāya — The Already-Accomplished Means
Siddhopāya (Sanskrit: siddha = already accomplished/existing + upāya = means; 'the means that is already accomplished') refers to Śrīman Nārāyaṇan Himself as the means of liberation — a means that requires no further accomplishment on the part of the seeker.
Contrast with Sādhyopāya: The opposing concept is sādhyopāya — means that must be accomplished through personal effort (karma yoga, jñāna yoga, bhakti yoga). These require long practice, qualification, and sustained effort across many lifetimes. Siddhopāya — Bhagavān Himself — is immediately accessible through prapatti (surrender), requiring no prior spiritual qualification.
Why Bhagavān Is the Upāya: Since Bhagavān is sarvajña (omniscient), sarvaśakta (omnipotent), and possesses nirhetuka kṛpā (causeless grace), He has no limitation in granting liberation. A jīvātmā need only surrender — and Bhagavān, as the ultimate means, does everything necessary for the soul's upliftment.
The Dvaya Mantra Context: The Dvaya mantra expresses the complete action of siddhopāya: 'I surrender to the feet of Śrīman Nārāyaṇan through the mediation of Śrī' — here Bhagavān with Śrī Mahālakṣmī is the siddhopāya; the seeker's prapatti activates this pre-existing means.