Slippery Slope Argument

Two important versions of the slippery slope argument are the logical slippery slope and the causal slippery slope. The basic form of the slippery slope argument is as follows: A particular action seems to be acceptable. But if this action takes place, then another, less acceptable action, will follow. This is followed by an even less acceptable action, and so forth. For example, someone might argue that legalizing prostitution will cause more marriages to break up, which will in turn cause the breakdown of the family, which will finally result in the destruction of civilization.

The logical slippery slope argument is best illustrated by the example of baldness. Removing one hair from an individual does not make a person bald. Neither does removing two hairs, or 100. Therefore, any line drawn between baldness and nonbaldness will be arbitrary. The problem with this argument is obvious: Just because one cannot specify the number of hairs that must be removed for baldness, it does not imply that we cannot identify a person as bald. It only implies that there may be some cases in which it is a toss-up whether we can label a particular person as “bald.”

A classic example of the logical slippery slope argument is found in the abortion debate. Some opponents of abortion have argued that human life must begin at conception, since no nonarbitrary line can be drawn in fetal development between conception and birth. However, this argument cannot stand on its own. It depends on a view of personhood that identifies the body at any point of development as being a person. Those who believe that personhood is present only with the coming of self-consciousness would hold that personhood comes much later in biological development than conception. More relevant to the sorites argument is the fact that just because a nonarbitrary line cannot be drawn in fetal development, it does not imply that no line can be drawn at all.

Most slippery slope arguments in ethics are causal. These are usually predictions: If one course of action is taken, it will lead to another course of action, and so on, until it results in actions that are clearly morally reprehensible. For example, an opponent of companies mining data from those who surf the Internet might argue that retrieving information that is not personally identifiable will lead to companies retrieving personally identifiable information, with the end result being a total loss of Internet privacy. This is a causal claim since the argument is that data mining of such information from Web surfers will cause the mining of personally identifiable information. The most plausible way to understand such causality is in a psychological sense. That is, opening the door to mining one class of Internet users' data removes psychological barriers to mining other kinds of data. The difficulty is that the claim is about what data mining companies might do in the future. It is much easier to look back in retrospect at actions and see a “slippery slope” than to make a prediction about future behavior.

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