Via a nice looking new blog called Benedictus Deus is this snippet from Pope Benedict on marriage.
To renew man, the Lord — alluding to these prophetic voices which always guided Israel towards the clarity of monogamy — recognized with Ezekiel that, to live this vocation, we need a new heart; instead of a heart of stone — as Ezekiel said — we need a heart of flesh, a heart that is truly human.
And the Lord “implants” this new heart in us at baptism, through faith. It is not a physical transplant, but perhaps we can make this comparison. After a transplant, the organism needs treatment, requires the necessary medicines to be able to live with the new heart, so that it becomes “one’s own heart” and not the “heart of another.”
This is especially so in this “spiritual transplant” when the Lord implants within us a new heart, a heart open to the Creator, to God’s call. To be able to live with this new heart, adequate treatment is necessary; one must have recourse to the appropriate medicines so that it can really become “our heart.”
Thus, by living in communion with Christ, with his Church, the new heart truly becomes “our own heart” and makes marriage possible. The exclusive love between a man and a woman, their life as a couple planned by the Creator, becomes possible, even if the atmosphere of our world makes it difficult to the point that it appears impossible.
The Lord gives us a new heart and we must live with this new heart, using the appropriate therapies to ensure that it is really “our own.” In this way we live with all that the Creator has given us and this creates a truly happy life.
As this blogger said "Isn’t this Pope fantastic?" I love this transplant analogy and I think it can be extended. In the realm of organ transplants often immune-suppressant drugs are given since the body is attempting to reject what it sees as foreign material. You can see the same thing happening in the parable of the sower and the seeds where some also end up rejecting what should be life-giving to them. Accepting the sacred heart of Christ to replace are stony hearts the same thing happens. Leading a life of holiness and humility can be fought by our ingrained habits and our thought processes that have not yet adapted. Our materialistic antibodies can kick in to try to deter us from turning towards God as we cling to our sinful habits and faults which we are loathe to give up. It is only through sheer grace that we can accept this new heart. Transplant patients often have to use these immune-suppressant drugs for their whole lifetime. We too must do the same thing when it comes to grace – the grace of final perseverance.
This analogy I believe goes well with my Divine Physician parody.