Impure Motives (Part 16 of Fallacies/Red Herrings)

A short installment this week. Part 16 of Red Herrings covers still more responses to arguments that distract from the argument rather than address it directly. This week we cover the appeal to motive.

Appeal to Motive

Scientist A says that man-made climate change is a real threat. Scientist A is a candidate for tenure at a well-known university, and the head of his department believes the same thing. This means that Scientist A’s motives are impure, and therefore his argument is false.

This is the appeal to motive, another subcategory of the argumentum ad hominem. Its special feature is that it’s only necessary to show that there is a possibility of a motive, however small. What’s missing is proof that (a) the motive actually exists, (b) if it does exist, it played a role in formulating the argument and conclusion, and (c) any other proof or evidence offered is ipso facto invalid.

It’s related to general claims of conflict of interest. In the run up to the Supreme Court hearings on the Affordable Care Act, accusations of conflict of interest have been leveled at three justices, two conservative and one liberal. Showing the potential for a conflict of interest isn’t the same thing as demonstrating that the votes of these justices is necessarily corrupt. In the particular instance, it’s more likely the case that the predispositions of the justices predate the events and actions leading to the charge.