Slippery slope isn’t automatically a fallacy. It’s a fallacy if you don’t articulate why A would lead to B.
The government using an anti-CSAM filter to further restrict, say, copyright infringements has precedent, so could be a valid slippery slope.
The idea people pushed that marriage equality would lead to people being able to legally marry their animals was fallacious because nobody could articulate a logical jump from same sec couples to interspecies.
Your last sentence seems to itself refute the point it is trying to make.
You refer to "marriage equality", not "same-sex marriage". So you presumably think that the justification for allowing same-sex marriage is not some consideration of whether recognizing same-sex marriages in particular is beneficial, but rather that the justification is that they must be allowed for "equality". That justification easily generalizes to any other case where someone wants to enter into a "marriage" that is not currently recognized.
[ Note: Personally, I think the state should have nothing whatever to do with marriage, obviating the entire issue. ]
Marriage equality is generally implied (if not expressly stated) that it is about humans. Functionally speaking, there's no evidence to show that people who like people of the same sex might move on to toasters. The movement was always about people. The lack of specificity was because the context was obvious, not because it was nebulous.
The next point along the slippery slope would more likely be forcing states to accept polygamous marriages of more than 2 people. Another point on the slope might be allowing siblings to marry (especially if they are the same sex so there is no danger of inbreeding).
Perhaps the reason why marrying toasters is unlikely to be anywhere on the slope is that, from the government's perspective, a marriage is a legal contract entered into by the parties. It's not clear what a one-sided legal contract with a toaster would look like, beyond the mere recognition of property ownership.
One possible extension, though, could be marrying a corporation, since they have legal personhood. Perhaps that right will be moot once polygamy becomes legal, or alternatively someone will try to make polygamy legal by attempting to marry a corporation owned by their two intended spouses.
It's not down the slope though, because nothing about being LGBT is "closer" to polygamy than existing marriage. They're not related in practice, function, or advocacy.
A slippery slope exists when there is a functional reason why one would cause the other. It's a fallacy when they're simply related by irrelevant association (in this case, their prohibition). Legalizing one thing for a good reason does not cause people to lose their minds and legalize dumb things.
> nothing about being LGBT is "closer" to polygamy than existing marriage.
Well, except that a polygamous marriage necessarily requires that 2 people of the same sex are married to each other. If the law still said that a man can only marry a woman, and a woman can only marry a man, then polygamy would be impossible without defining the number of people in a marriage.
(I suppose that technically marriage could be defined to be non-transitive, such that a man's two wives weren't married to each other, for example, but that would seem like an arbitrary and discriminatory restriction. Also, the government could give legal recognition to more than 2 sexes, but that seems like a point on a different slippery slope.)
Anyway, I think that for a lot of people, the insistence that marriage should be between one man and one woman was some combination of "it's always been that way", "that's how you create a child", and "that's the only type of marriage my religion allows", but SCOTUS set the precedent that none of those are legally sufficient to prevent a redefinition of marriage.
So it's not that one type of monogamous marriage is "closer" to polygamy than another type of monogamous marriage. The court doesn't have to take into account the wishes or definitions of already-married couples, and instead looks at what grounds the government has for refusing to grant legal recognition for plaintiffs who believe they are married to each other. I haven't looked at the specific rulings and legal arguments, but my impression is that states would now have fewer grounds for opposing a further, more expansive, redefinition.
>a polygamous marriage necessarily requires that 2 people of the same sex are married to each other
I never heard of that idea before, but I didn't really know anything about how it is in fact defined where it is legal and customary.
I found something that describes the "Law of Marriage Act of 1971" of Tanzania:
"Under Section 10(1) of the Act, a marriage is defined as “the
voluntary union of a man and a woman, intended to last for their joint lives,” and may either be monogamous or polygamous (or potentially polygamous). Further, under Section 57, no wife in a polygamous marriage holds a superior position in matrimonial homes than any other wife."
I read that as saying that polygamy consists of a set of bilateral relationships having one person in common, and not a complete graph of all possible relationships between the individuals.
The paper I found that in seems to be about issues arising in divorce in Tanzania.
The problem is stated as:
"Because non-divorcing co-wives cannot be a party to divorce proceedings, and only parties can claim a stake in marital assets, the LMA currently offers no means for non-divorcing co-wives to claim a stake in marital property"
This sounds to me like wives are not considered to have a relationship to each other, and that has social implications which are important.
One can't overgeneralize based on this one source and one country, but it tends to make me more confident in my guess that "non-transitive" is the norm.
Thanks for researching that. I agree that, in practice, societies which allow polygamy probably have non-transitive marriages, and they could theoretically allow women to have two husbands so as not to give men more rights than women.
In an alternate reality where the US constitution happened to define marriage as between "a man and a woman", I could imagine activists pushing for states to allow polygamy so that two men or two women could "indirectly" marry, and pressuring the government to avoid the issues experienced in Tanzania by writing laws and policies which effectively treat the connection between the leaf nodes as equal to their connection to the root node when considering questions of divorce, taxation, inheritance, parenthood, etc.
The government using an anti-CSAM filter to further restrict, say, copyright infringements has precedent, so could be a valid slippery slope.
The idea people pushed that marriage equality would lead to people being able to legally marry their animals was fallacious because nobody could articulate a logical jump from same sec couples to interspecies.