The Real Slippery Slope: Logic, Fallacy, and American Decline

6 thoughts on “The Real Slippery Slope: Logic, Fallacy, and American Decline”

  1. If you could please elaborate on the ‘deepest issues’ not understood by those of use who consider consent a large part of the ‘consensual sexual relationship’ as outlined in premise #1 of your argument I would be very appreciative.

  2. Dr. Groothuis,

    Thank you for posting the reductio ad absurdum. And thanks for your work on the blog.
    I agree with the conclusion of your RAA. But is the argument sound? Here is the argument as presented:

    1. If same-sex marriage is moral, then any consensual sexual arrangement (involving marriage or not) is moral.
    2. Same-sex marriage is moral.
    3. Therefore: consensual polyamory, incest, pedophilia, and bestiality are moral.
    4. But (3) is absurd, since these acts are immoral.
    5. Therefore, it is false that same-sex marriage is moral; it is immoral. This is by reductio ad absurdum.

    The argument is deductively valid. But is there is an equivocation on ‘moral’? In (1) and (2), ‘moral’ could seem to refer to non-objective (i.e., culturally relative or individually relative/subjective) morality, to morality that is a mere human construct. But in (4), ‘immoral’ seems to refer to objective morality. (4) seems to state that the acts noted in (3) are objectively morally wrong. If the meaning of ‘moral’ switches in the argument, then there is an equivocation and the argument is unsound.

    If there is no equivocation, then ‘moral’ is univocal in the argument. If so, is ‘moral’ univocal in the objective sense or in the non-objective sense? If the latter, the RAA would seem to be weakened, since the absurdity of (3) would be only non-objectively absurd, because the acts wouldn’t be objectively immoral. (Of course, they wouldn’t be objectively moral, either.)

    But your meaning appears to be the former. If so, perhaps it would be beneficial to explicitly note the objective sense.

  3. Suppose ‘moral’ univocally means “objectively moral.” An expanded version of the argument might look something like this:

    1. There is objective morality. (Premise)
    2. If there is objective morality, then an act can be objectively morally wrong. (Premise)
    3. Thus, an act can be objectively morally wrong. (1,2 MP)
    4. Same-sex marriage is objectively morally permissible. (Suppose for RAA)
    5. If marriage is a mere human construct, then marriage does not have an objectively real nature and vice versa. (Premise)
    6. Thus, if marriage is a mere human construct, then marriage does not have an objectively real nature. (5, SIMP)
    7. If same-sex marriage is objectively permissible, then marriage is a mere human construct. (Premise)
    8. Thus, marriage is a mere human construct. (4,7 MP)
    9. Thus, marriage does not have an objectively real nature. (6,8 MP)
    10. If marriage does not have an objectively real nature, then human beings can construct whatever definition of marriage they desire as long as the marriage includes proper consent. (Premise)
    11. Thus, human beings can construct whatever definition of marriage they desire as long as the marriage includes proper consent. (9,10 MP)
    12. If (11), then any merely human constructed sexual arrangement is an objectively permissible definition of marriage as long as the arrangement is consented to by those involved who are able to provide consent. (Premise)
    13. Thus, any merely human constructed sexual arrangement is an objectively permissible definition of marriage as long as the arrangement is consented to by those involved who are able to provide consent. (11,12 MP)
    14. If (13), then polyamory, incest, bestiality, and pedophilia are objectively permissible types of marriage as long as they are consented to by those involved who are able to provide consent. (Premise)
    15. Thus, polyamory, incest, bestiality and pedophilia are objectively permissible types of marriage as long as they are consented to by those involved who are able to provide consent. (13,14 MP)
    16. But (15) is absurd, since these acts are objectively impermissible (i.e., wrong) regardless of consent. (Premise)
    17. Thus, on the assumption of (4), these acts are objectively permissible and these acts are objectively impermissible. (15, 16 CONJ)
    18. Thus, it is false that same-sex marriage is objectively morally permissible. (by RAA, 4-17)
    19. If it is false that same-sex marriage is objectively morally permissible, then same-sex marriage is objectively morally wrong. (Premise)
    20. Thus, same-sex marriage is objectively morally wrong. (18,19 MP)

    * By an act being permissible, I mean there is no objective moral obligation to not do the act. In other words, PEp ↔ ~OB~p (where PE means permissible, and OB means obligatory). I.e., if action p is permissible, then there is no obligation to avoid p and vice versa. And if there is an obligation to avoid p, then p is impermissible.

    ** The argument rests on the assumption that if marriage has an objective nature (i.e., a set of essential properties), then that nature precludes same-sex union. In other words, the traditional definition of marriage aligns with the objective nature of marriage, but same-sex union does not align.

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