The Arya Samaj's most distinctive and most contested practice is shuddhi, a purification ritual used to admit or readmit individuals to Hindu religious identity. Dayananda argued that since Hinduism, properly understood as Vedic religion, had no original doctrine excluding converts, the loss of members to Islam and Christianity through centuries of conversion could in principle be reversed through a formal rite of return. In practice, shuddhi campaigns in the early twentieth century extended beyond readmitting the previously converted to actively seeking new converts from other religions, which brought the Samaj into direct and sometimes heated competition with Christian missionary organizations and Muslim reform movements operating in the same regions.
This activism placed questions of religious identity and conversion at the center of Indian public life well before independence, and the Samaj's rhetoric and organizing methods influenced later Hindu nationalist movements, a connection historians continue to weigh carefully given how different Dayananda's own rationalist, anti-ritual theology was from some of what came after it.
Alongside its more contested activities, the Arya Samaj's social reform record is substantial: it opposed child marriage and campaigned for widow remarriage and women's education at a time when both were widely resisted, and its network of schools trained generations of students in a curriculum that deliberately combined Sanskrit learning with modern science.