His most recent post on the subject is spot-on, methinks, and it prompted me to recall a down-to-earth analogy that a priest-friend of mine used in a humdinger of a homily he preached on contraception last year. The analogy isn't his originally; it's also been used by Christopher West — and maybe others, too — but I hadn't heard it before:
Now, Natural Family Planning is not Catholic contraception. I repeat, Natural Family Planning is not Catholic contraception. Let me give you an example:
Suppose John and Mary are planning a wedding. They are sending out invitations and wonder if they should send an invitation to their good friend Jesus. Jesus has always been gone on the last 7 days of every month, and their wedding is at the end of the month. John and Mary, knowing Jesus is always gone at the end of the month, send him an invitation anyway because they would like Jesus to be there. This is Natural Family Planning, the invitation is there for God.
But suppose John and Mary like Jesus, but they do not want him at their wedding. Now they know he is going to be gone when the wedding is scheduled, but just to make sure he does not accidentally show up by some fluke, they send him a note saying that under no circumstances is he to come to the wedding. This is artificial contraception; it sends a note saying NO to God.