Let me respond to Justin Katz’s post that was a response directed at me.
Jon Rowe writes:
[Polygamy, incest, bestiality,] & Homosexuality each wholly distinguishable phenomenon. The only thing they have in common is being frowned on by tradition. But equally has interracial couplings. Thus, homosexuality is no MORE logically related to these things than are interracial couplings. The bottom line of my point is examine each on a case by case basis.
There are various ways to argue against this point, but most relevant to the discussion, I'd say, is that there's an extra step required for same-sex marriage to follow interracial sex and marriage. To allow such activities for couples of differing race, all that was required was to assert that there was no significant difference between the races. Self evidently, therefore, there is no significant difference between the type of sex or the form of marriage indicated.
The same is not true for homosexual couples. In their case, it is patently absurd to argue that there is no significant difference between the sexes (although some try to argue just that). The equivalence that must be added to the mix is between the types of sex. And therein lies the step too far.
But here is the problem for Justin’s “Slippery Slope” side: He has just moved from, “slippery slope to P, I, & B” to “how homosexual marriages will affect society based on the differences between hetero and homo sex.” These are two distinct issues. Leave aside bestiality for a moment. Say we have a marriage between one man and more than one woman that has only heterosexual sex (common for of polygamy), or a marriage between a brother and a sister…as long as procreative vaginal sex is involved in both circumstances, we could also say that “there is no significant difference between the type of sex.” Regarding “form of marriage,” a brother and sister marriage also does not violate the one man/one woman paradigm. Under the same slippery slope logic, we could argue, “recognize interracial marriage today, and you’ll have incestuous ones tomorrow.”
The point about the slippery slope is that it is a logical fallacy—that is we can always ask, “if we apply the same rule to another circumstance, how do we draw the line here and not there?” with every single policy, even the good ones that we all support. But the line has to be drawn somewhere—that’s why I argue, “examine each on a case by case basis.”
For instance, let’s say that a federal court recognizes same-sex marriage and explicitly relies on the Loving case as authority. Back when Loving was decided, the anti-miscegenationists raised the same slippery slope fears. Once a federal court uses Loving to support same-sex marriage, the racists could say, “HA, we were right! Interracial marriages led us down a slippery slope to same sex marriage.”
The point that Eugene Volokh makes is that even though the slippery slope is a logical fallacy, it is alive and well in a legal system that relies on reasoning through analogy and past precedent. But the point still remains that every good policy that we all support can—via the slippery slope mechanism—be taken to support policies that we do not desire.
So how do we stop the slippery slope in the courts? By limiting the case to the facts involved, or reading the rules in a more narrow sense. How do we limit the Loving decision? By only applying it to racial discriminatory cases. How would we limit a same-sex marriage ruling? By only applying it to gender discriminatory cases. And when we get involved in the “specifics” of each circumstance, we find that there are entirely different reasons for and against each of these cases. And it’s in those distinctions where social/legal policy can find their reasons for not extending the logic of one circumstance to another.