Here is an excerpt from Budziszewski’s recent book On the Meaning of Sex (OMS). OMS was an excellent, albeit short, book that I would recommend to anyone interested in natural law sexual ethics. I have a book review that will be featured on Apologetics 315 on July 7th. So stay tuned for that! But here are a couple of things Budziszewski has to say that’s taken straight from his book:
What then are the natural meanings and purposes of the sexual powers? One is procreation—the bringing about and nurture of new life, the formation of families in which children have moms and dads. The other is union—the mutual and total self-giving and accepting of two polar, complementary selves in their entirety, soul and body. These two meanings are so tightly stitched that we can start with either one and follow the threads to the other. (24)
With regard to the unitive meaning, he writes:
We join ourselves by doing what? By an act which is intrinsically open to the possibility of new life. In other words, whenever I give myself sexually, I am doing something that cannot help but mean that happy chance […] Now for two persons to give themselves to each other totally is to give what they are wholly; what they are wholly includes their bodies; and into these bodies is written the potentiality to bring a third person into being. […] Mutual and totally self-giving, strong feelings of attachment, intense pleasure, and the procreation of new life are linked by human nature in a single complex of meaning and purpose. For this reason, if we try to split them apart, we split ourselves. (27-29)
The purposes of unity and procreation cannot be separated, and this is the kind of separation we see in same-sex marriage (I believe Budziszewski briefly points that out, and if I am mistaken that he does mention that, my apologies).