original article

For those who are only slightly schooled in debate, there’s a more subtle distinction to be made regarding what is or is not argumentum ad hominem. Specifically, it only counts if the commentary about the person is intended or serves to undermine their credibility regarding the matter under discussion. Gratuitous insults, while unwelcome for other reasons, are not argumentum ad hominem.

Furthermore, it is not argumentum ad hominem if the person’s character and/or credibility are actually relevant to the discussion. For example, if the topic is “X is child molester” then commenting on X’s sexual history does not constitute an ad-hominem attack. Similarly, if X is attempting argumentum ad verecundiam (less pretentiously known as an appeal to authority: “You should agree with me because I’m an expert.”) then commentary on X’s credentials (“Some expert, you’re really a high-school student with a D average.”) is entirely appropriate; X has made their credentials relevant by being the one to mention them.

In short, not every comment about a person is argumentum ad hominem. Many people on the net have learned to “take the high ground” by calling any personal comment as an an ad-hominem attack, even as they themselves indulge in appeals to authority and all manner of other fallacies. Most such claims are, in fact, a sort of second-order ad-hominem attack; their intent is to undermine the accused’s credibility by making them out to be a “bad” debater.

P.S. I highly recommend Don Lindsay’s list as a reference to common logical fallacies. Re-reading the list periodically will not only help you to recognize fallacious reasoning by others, but also to avoid fallacies yourself.