Ad Hominem - Circumstantial

Description:

The argument attacks a position by appealing to the vested interests of a person who holds the position.

Examples:

"You can hardly convince me that increases in the military budget are desirable when I happen to know that you work in a munitions factory."

 "We can safely ignore Mitt Romney's arguments that tax cuts for the very wealthy would help the economy. As a member of the 1%, he is only looking out for the interests of himself and his rich friends."

Discussion:

In many context--especially law, but also journalism, politics and business--we pay close attention to conflicts of interest, and we are right to do so. Judges are required to "recuse" themselves from cases in which their personal interests could influence their decision. We need to know when journalists are reporting on the same institutions that pay their salaries. We cringe when we discover that our political leaders receive campaign contributions from companies with an interest in how our leaders vote. From experience we know that decisions are influenced by the vested interests of the decision maker. We have legitimate reasons to guard against conflicts of interest.

The Ad Hominem - Circumstantial fallacy persuades by mimicking our legitimate concerns over conflict of interest. However, arguments are not decisions. A person with a conflict of interest may reason badly (and thus make a bad decision), but his conflict of interest need not influence our assessment of his argument. We need to decide whether or not to accept his argument. The decision to be made is ours, not his. Hence we would be right to be concerned with our own conflicts of interest, but his conflicts of interest are an irrelevant distraction.

Source: Contemporary writers distinguish the various forms of ad hominem fallacy. I first became aware of the distinction between the circumstantial ad hominem and the abusive ad hominem from Irving M. Copi, Introduction to Logic, the earliest edition of which appeared in 1953. It is possible that Copi was the first logician to draw this distinction, but I have always assumed that he took it from an earlier source.

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