Paul argues from this very point. Our moral life should square with the fact that God has made us His own. So, imperfect though we are, we still are saints. And though we are saints, we must continually grow. We may have many defects of character and thought, as did the saints at Corinth, but we still belong to God, and, therefore, are called to constant improvement.
Saints are imperfect people moving toward perfection.
We have the inspiration and motivation to do this because we already belong to God, who daily gives us further opportunities to grow. The appeal to become truly good persons is not that by doing so we can become saints, but rather that being saints already, we can become truly good people. Unfortunately, many of us have bought into the Catholic concept that saints are a very rare group of perfect people. In fact, according to this teaching, one is not a saint in this lifetime, but becomes one, often centuries later, by the action of the church. That is why Paul addresses almost every letter to the saints.