It has been a while since I started reading The Last Superstition and I think an update is due. The book spends chapter 2 discussing Greek philosophy, specifically Plato and Aristotle.This lead directly into chapter 3's discussion of the medieval philosopher Thomas Aquinas.
Interspersed through these chapters are ad hominem attacks against Dawkins, Hitchens, Harris and Dennette, the infamous New Atheist. Much of these attacks are due to the apparent ignorance of this group, especialy those with training in philosophy, about the metaphysics and arguments of Aristotle and Aquinas. Since Aristotle's ideas as well as Aquinas' improvements have been rejected in modern philosophy, this omission should hardly be surprising.
As for the arguments themselves, Feser does give quite a few arguments for the existence of God. Unfortunately, due to the length required to sufficiently explain the argument and give my objections, I do not have the room to refute them here.
However, once argument that was given was with regards to sexuality. Basically, he objects to all sex acts that do not involve a man having vaginal intercourse with a woman with out and birth control. He argues that the biological nature or final cause of sex is procreation and thus any sex act that does not end with the man freely ejaculating into the women in such a way that is conducive to pregnancy is immoral.
This, of course, is silly. The biologically final cause of an action does not determine, in and of itself, whether or not an action is immoral. Consider this, the biological nature of walking is to move a person from one point to another. Walking on a treadmill frustrates the biologically final cause of walking. Using the same logic, we should oppose treadmills.
One might point out that walking on a treadmill is not as bad as using a condom because a condom prevents the sex act from producing life and nothing is more valuable then life. However, not having sex also prevents life and there is nothing inherently immoral about that. No one would even attempt to claim that treadmills are immoral. Why not even though they evade the biological purpose of walking?
Treadmills have human derived final cause of improving health. Because of our ability to reason we can over rule a biological final cause with our own desired final cause. Like walking has uses beyond just moving us from one point to another so too sex has uses other then simple procreation.
Based of this argument, Feser claims that marriage is about procreation. Husband and wife work together to support the family. This is not what we mean by marriage in modern times. In the past when marriage was solely about 2 people coming together to start a family, marriage as between a man and woman only made sense. However, the modern version of marriage is perfectly suited for couples who want no children as well as gay couples. Due to the existence of adoption agencies, if a gay married couple decided they did want to raise children, that option is as open to them as to heterosexual couples.
The mistake is to assume that the only proper final cause is the biological but that only leads to absurdity.