[Søren] Kierkegaard has a beautiful devotional titled “Purity of Heart is to Will One Thing.” The basis for the book is James 1:8 and he spends the majority of the space in the book psychologically evaluating what it means to will one thing and what many of the barriers are to willing one thing. The title of the work alone speaks beauty and simplicity to me. I believe Kierkegaard is getting at the heart of Jesus with the idea behind this book. Jesus said that only one thing is necessary and he said that the law is fulfilled in one commandment: Love God and love neighbor.
One of my favorite illustrations in the book is when Kierkegaard writes of a man who is courting a wealthy woman. The double-minded man, the man who does not will only one thing, is pleased by the fact that his marriage to the woman will result in financial gain. The man without a pure heart allows his love for the woman to be tainted by her situation and the gain which will come to him as a result. The man who courts the wealthy woman and wills only one thing, the man with a pure heart, hates any financial gain he may come to acquire by his marriage to the woman. The man has a disdain for the woman’s wealth, not out of jealousy or in any way which causes feelings of contempt for the woman, but for quite the opposite reason. The man has contempt for the woman’s wealth because it presents the possibility of his love for her losing its purity. The man who wills only one thing wants to do nothing but love the woman with his whole heart and with a pure heart. Any other thing which may cause him to love the woman with any less than a whole and pure heart is an enemy. He wants only to love the woman and he wants nothing to get in the way. The man with the pure hearts acts in a way which eliminates other possible competitors for his love.