While same-sex marriage seems to have momentum in its favor in the United States, there is still considerable opposition to its acceptance. This opposition is well stocked up with stock arguments against this practice. One of these is the slippery slope argument: if same-sex marriage is allowed, then people will then be allowed to marry turtles, dolphins, trees, cats, corpses or iPads. Since this would be bad/absurd, same-sex marriage should not be allowed. This is, of course, the classic slippery slope fallacy.
This is a fallacy in which a person asserts that some event must inevitably follow from another without any argument for the inevitability of the event in question. In most cases, there are a series of steps or gradations between one event and the one in question and no reason is given as to why the intervening steps or gradations will simply be bypassed. This “argument” has the following form:
1. Event X has occurred (or will or might occur).
2. Therefore event Y will inevitably happen.
This sort of “reasoning” is fallacious because there is no reason to believe that one event must inevitably follow from another without adequate evidence for such a claim. This is especially clear in cases in which there are a significant number of steps or gradations between one event and another.
In the case of same-sex marriage the folks who claim these dire results do not make the causal link needed to infer, for example, that allowing same-sex marriage will lead to people marrying goats. As such, they are committing this fallacy and inviting others to join them in their error.
While I have written a reply to this fallacious argument before, hearing someone making the argument using goat marriage and corpse marriage got me thinking about the matter once again.
Using goat marriage as an example, the idea is that if same-sex marriage is allowed, then there is no way to stop the slide into people marrying goats. Presumably people marrying goats would be bad, so this should be avoided. In the case of corpse marriage, the gist is that if same-sex marriage is allowed, then there would be no way to stop the slide into people marry corpses. This would presumably be bad and hence must be avoided.
The slide down the slippery slope, it must be assumed, would occur because a principled distinction cannot be drawn between humans and goats. Nor can a principled distinction be drawn between living humans and corpses. After all, if such principled distinctions could be drawn, then the slide from same-sex marriage to goat marriage and corpse marriage could be stopped in a principled way, thus allowing same-sex marriage without the alleged dire consequences.
For the slippery slope arguments to work, there must not be a way to stop the slide. That is, there is a smooth and well-lubricated transition between humans and goats and between living humans and corpses. Since this is a conceptual matter rather than a matter of actual slopes, the slide would go both ways. That is, if we do not have an adequate wall between goats and humans, then the wall can be jumped from either direction. Likewise for corpses.
So, for the sake of argument, let it be supposed that there are not such adequate walls—that once we start moving, we are over the walls or down the slopes. This would, apparently, show that same-sex marriage would lead to goat marriage and corpse marriage. Of course, it would also show that different sex-marriage would lead to a slide into goat marriage and corpse marriage (I argued this point in my book, For Better or Worse Reasoning, so I will not repeat the argument here).
Somewhat more interestingly, the supposition of a low wall (or slippery slope) between humans and animals would also lead to some interesting results. For example, if we allow animals to be hunted and there is no solid wall between humans and animals in terms of laws and practices, then that would put us on the slippery slope to the hunting of humans. So, by the logic of the slippery slope, we should not allow humans to hunt animals. Ditto for eating animals—after all, if same-sex marriage leads to goat marriage, then eating beef must surely lead to cannibalism.
In the case of the low wall (or slippery slope) between corpses and humans, then there would also be some odd results. For example, if we allow corpses to be buried or cremated and there is no solid wall between the living and the dead, then this would put us on the slippery slope to burying or cremating the living. So, by the logic of the slippery slope, we should not allow corpses to be buried or cremated. Ditto for denying the dead the right to vote. After all, if allowing same-sex marriage would warrant necrophilia, then denying corpses the vote would warrant denying the living the right to vote.
Obviously, people will want to say that we can clearly distinguish between animals and humans as well as between the living and corpses. However, if we can do this, then the slippery slope argument against same-sex marriage would lose its slip.