Bernard of Clairvaux (1090-1153) was known as one of the church’s greatest orators. He was also well known as one of the most "God-fearing and holy" monks who ever lived. He gave powerful impetus to the monastic movement during his lifetime and far beyond. He was reared in France by a knightly father and a godly and deeply religious mother. At the age of twenty-two he became a neophyte in the monastery in Citeaux (France). Three years later, as a young man of only twenty-five, he was sent out as the leader of a group of men to found a new monastery in Clairvaux. Though offered high positions in church leadership he consistently turned them all down to remain at Clairvaux for his entire life.
To the surprise of some Protestants his writings had a deep impact on both Martin Luther and John Calvin, among others. Over his 500 personal letters, hymns which are still sung, doctrinal treatises, and sermons, eighty-six on the Song of Solomon alone, we have quite a treasure of spiritual writing from this much admired Christian. One of his best-known classic works is titled On the Love of God. Here he gave deep insight into deep mystical devotion to Christ.
Should we love God because he deserves our love or because it is to our advantage to love him? In a sense this is the kind of question that the popular evangelical writer John Piper poses by his "desiring God" thesis. But Piper tends to answer this question in a way that Bearnard would, I think, have not been fully happy with. Bernard would say that the reason we should love God is found "in God himself." He goes on to argue that the reasons we should give special attention to our love for God is because God gave himself to us in spite of our unworthiness. We should, simply put, love God "because he first loved us." God deserves our love even though he does not need my love. God loves his enemies, and that gratis, so we should love him back.
I may be wrong about this but it seems to me that John Piper, and those who follow his misnamed concept of Christian hedonism, reject the idea that we should love God in this way because we would then be loving God for what he has done for us, thus the "debtor’s ethic" would be the result. I do not think Bernard would make such a distinction at all. Bernard even uses the term "debtor" in the same section of this classic work where he speaks of the "Degrees of the Love of God" and "Why God Should Be Loved."
We love God because he first loved us, thus we have a debt to love him. We also love him because it is in our best interest to do so. Bernard would say both are true.