Aquinas and Homosexual Sex – Part 2: Argument Structure

Aquinas and Homosexual Sex – Part 2: Argument Structure December 4, 2020

Detail from “Triumph of St. Thomas Aquinas over Averroes” by Benozzo Gozzoli (1420–97)

 

A THOMIST ARGUMENT AGAINST HOMOSEXUAL SEX

The argument that I will now analyze (and evaluate later) comes from an article by Timothy Hsiao published in The Heythrop Journal in 2015: “A Defense of the Perverted Faculty Argument against Homosexual Sex” (hereafter: PFA).  The main argument is summarized in section III of the article. Here are the main premises/claims of the argument as stated in the summary:

1. It is always immoral to misuse a bodily faculty.

2. Misusing a bodily faculty always involves rejecting the human good.

3. Sexual activity exists for the sake of procreation and unity.

4. All sexual activity that is not open to the creation of new life is immoral.

5. Those who engage in homosexual conduct bring their sexual faculties to bear on a member of the same sex.

6. Those who bring their sexual faculties to bear on a member of the same sex direct the function of sex to an end that is intrinsically unfit for the direction of sex towards the generation of new life. 

7. Homosexual activity is immoral.

The fourth statement is clearly a key premise, and that last statement is clearly the conclusion.  Thus, we can initially summarize this argument using just those two key statements:

4. All sexual activity that is not open to the creation of new life is immoral.

THEREFORE:

7. Homosexual activity is immoral.

There is a key premise that is missing, however, in this initial summary of the argument in PFA.  “Homosexual activity” needs to be linked to “sexual activity that is not open to the creation of life” in order to make this summary argument logically complete or valid:

4. All sexual activity that is not open to the creation of new life is immoral.

A. All homosexual activity is sexual activity that is not open to the creation of new life.

THEREFORE:

7A. All homosexual activity is immoral.

This core argument is logically VALID:

All Bs are Cs.

All As are Bs.

THEREFORE:

All As are Cs.

I take it that this categorical syllogism is the core argument in PFA.  Any other claims made in PFA are relevant ONLY IF they provide support for premise (4) or support for premise (A).  Any additional statements that don’t function as REASONS or EVIDENCE in support of (4) or in support of (A) are IRRELEVANT to the evaluation of this core argument.  In order to evaluate the core argument in PFA, we need to determine whether premise (4) is TRUE or FALSE, and to determine whether premise (A) is TRUE or FALSE.  The logic of the summary argument is VALID, so the evaluation of this argument depends on the truth or falsehood of these two key premises.

Premise (A) appears to be TRUE.  If so, then the evaluation of this core argument in PFA would come down to the one issue of whether premise (4) is TRUE or FALSE.

However, premise (A) is not entirely clear.  So, I’m not willing to accept this premise as being TRUE unless and until the meaning of this premise is clarified.

In the next post of this series, I will examine premise (A) more closely, to see if I can clarify the meaning of this premise sufficiently to determine whether it is TRUE or FALSE.


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