"Looking at the lives of the saints we see their heroism, extraordinary virtue, profound intimacy with our Lord. They can seem distant, if not in time and place, then certainly in experience and stature. A common misunderstanding is to think of them as the fortunate few, almost as if they won the divine lottery. When we read of St. Paul running his race, we, the spiritual hoi polloi, run the danger of contenting ourselves with observer status in this most existential and dramatic of all contests. The problem is that we too often think holiness some arcane subject, when all along, the Church has clearly laid out its itinerary for us through her own spiritual masters and teaching. Knowledge of the spiritual life requires understanding of the Church's teaching on grace. Spiritual theology deals with understanding mechanics of this teaching and how to employ it. Lacking this understanding, we are left with the descriptive method that tends to convert the spiritual life into a disjointed collection of experiences. We end up with a more psychological-experiential presentation of the spiritual life than a theological one. When God created man according to his image and likeness, he made human nature in a specific way, with a spiritual structure, though natural, capable of receiving the supernatural structure imposed by grace. For example, the intellect, a purely spiritual yet natural faculty within our nature, receives the light of faith through grace and thus assents to truths that can only be known supernaturally. The light of grace affords us the ability to understand things that would otherwise remain hidden to our natural mind. In heaven, in fact, God gives the mind what is called the light of glory, the supernatural grace of being capable of beholding his Face without self-destructing; for no man can see my Face and live (Ex 30:20). A cornerstone of the Classical Tradition teaches us that grace builds on nature. What this means is that God created human nature in such a way that it would be capable of spiritual actions in the natural order - like having a conversation, thinking syllogistically, etc. When grace is superimposed on human nature, the spiritual elements of the human nature - namely, the intellect and the will, become capable of realizing supernatural actions, working above and beyond their own nature, while employing it more fully. The theological virtues of faith, hope, and love are examples of this, as are the infused virtues. All of this is thanks to grace. And grace is the beginning of holiness and, indeed, eternal life. The measure or the perfection of the spiritual life is the degree of participation by the individual Christian in the sanctity and perfection of God. In other words, how holy you are is determined by the degree of sanctifying grace you have. "It is the will of Jesus Christ that the whole body of the Church, no less than the individual members, should resemble Him." The more you are like God and participate in his nature, the holier you are." This book is based on the perennial teaching of the Church on the doctrine of grace: what it is; what it does; and how to grow in it. It draws from Scripture, the writings of Thomas Aquinas, Teresa of Avila, and John of the Cross.