Augustine of Hippo (354–430 AD) develops the Western doctrine of original sin in his controversies with the Pelagians. Pelagius taught that humans have genuine free will and can choose good without special grace — sin is individual acts, not a transmitted condition. Augustine counters: Adam’s sin transmitted both guilt and a corrupted nature to all his descendants through biological generation (specifically through concupiscence — disordered sexual desire — in the act of procreation). All humanity is therefore a massa damnata (condemned mass) deserving damnation, from which God graciously rescues some. This Augustinian doctrine shapes all subsequent Western theology — Catholic, Lutheran, Reformed. The Eastern Orthodox tradition has a different anthropology: it accepts the transmission of mortality and the tendency to sin through Adam, but not the transmission of guilt. The Immaculate Conception of Mary (defined as dogma in 1854) is the Catholic resolution of the problem of Mary’s relationship to original sin.