On slippery slope arguments

There are some arguments which I will likely never be persuaded to use. One such method of argumentation is the slippery slope (SS):

  1. If A occurs, then B will necessarily (or very probably) occur.
  2. If B occurs, then C will necessarily (or very probably) occur.
  3. [Repeat conditional premises as necessary]
  4. C is an undesirable event.
  5. In order to prevent C, it is necessary to prevent A.

SS arguments are very commonly fallacious, even though it is a matter of content and not form that makes them so. (A philosophy professor of mine pointed out, quite rightly, that they are simply extended forms of modus tollens and, less commonly, modus ponens.) This tendency toward fallacy is one of the main reasons I dislike them, and I believe that this tendency is due to the utter difficulty in thoroughly establishing the necessity of any given event.

Some events, of course, can be established as an event with almost complete certainty; for instance, lighting the fuse that appears to lead directly to a large amount of explosives will almost certainly result in an explosion. Of course, there are a number of plausible alternatives: the flame on the fuse might burn out; the fuse itself might not be intact in its path to the explosives; the explosives themselves might be duds; etc. (My perhaps antiquated analogy demonstrates why such an endeavor would more likely be aided with timers or remote detonating mechanisms, but there are conceivable weaknesses with those methods as well.)

Moreover, in the instances where SSs are utilized, there is a future outcome which almost certainly cannot be determined. Consider the common fallacy of gay marriage: The problem, according to those opponents of such a proposal, is that permitting anything but heterosexual marriage as a legally sanctioned arrangement will result in all sorts of things that we would not want (presumably because they are depraved or immoral), like people marrying animals, children, or close family. Opponents object – reasonably, it is emphasized – that none of these things need occur because of gay marriage; rather, it is simply a scare tactic used to oppose the measure in the legal sphere.

The arrogance that tends to be associated with the use of this fallacy, in short, is why I don’t want any part of it. I can’t see into the future, and neither can you, and we will both be better off with that realization.


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