|The converse accident fallacy (also known as reverse accident, and “a dicto secundum quid ad dictum simpliciter”) is a deductive fallacy that is committed in a statistical syllogism when an exception to a generalization is wrongly called for. That is, an exception to a generalization is applied to cases where the generalization should apply.
This fallacy is opposed to the accident fallacy (discussed in the previous episode) insofar as the accident fallacy applies a generalization indiscriminately even to a clear exception, while the converse accident fallacy makes an exception to a generalization indiscriminately even for cases where the generalization should apply.
The inductive version of this fallacy is called hasty generalization (to be discussed in a later episode).
The slippery slope fallacy (to be discussed in a later episode) is the converse accident fallacy when used in the following context: namely, in an argument that claims that some insignificant event will result in a chain of events that produce an undesirable result, but without the arguer quantifying the likelihood of each step in the chain. The fallacy is in failing to support the argument by quantifying each step.
Example 1 (of converse accident):
The argument is a converse accident fallacy because the medical exemption from the marijuana prohibition is applied to cases where the grounds for the exemption don’t apply. Notice that the argument is a fallacy regardless of one’s view of the prohibition. A person who argues against the prohibition needs to at least try to use relevant grounds, otherwise he is engaging in sophistry (the dishonest use of fallacies in debate).
By changing the wording, we get the slippery slope version of the above example, namely: “If we allow people with glaucoma to use medical marijuana, then eventually it will become acceptable to allow anyone to use marijuana.”
The argument is a converse accident fallacy because, as in example 1, the medical exemption from the general rule is applied to cases where the grounds for the exemption don’t apply.