The present research proposes to make a theological synthesis of the theology of grace in Saint Augustine and the dialectical theology of Karl Barth. And to show that, although the two used Paul s letter to the Romans as a basis to support their respective theologies, they used completely different epistemologies. Our research is intented to show that while St. Augustine made all things depend on Divine Grace, crediting Christ with the merit of everything, Karl Barth over- ontologized the theme of sin. Our research aims to show that, although the two worked too hard on the words sin and redemption, words that gravitate throughout salvation history, the scope of St. Augustine s theology is in grace. Meanwhile, Karl Barth placed more emphasis on the issue of sin and its catastrophic effect, which established a crisis between God and man. Hence the theology of crisis. But also dialectical theology, which takes place through self-giving and self-communication between God and humanity, since the Not-God was overcome from the yes pronounced through the works of Christ.