I would switch the order of DH1 and DH2. A tone argument is very rarely relevant to the substantive dispute. In most cases, the tone of an article shouldn't lead you to update your belief in the conclusion. An ad hominem argument, on the other hand, is often substantively relevant, especially given the power of motivated reasoning. It is entirely reasonable to lower your credence in the conclusion of an article arguing that senators are underpaid once you discover that the author of an article is a senator. Of course, if you have already evaluated the argument itself, and are fairly confident in your evaluation, then learning the identity of the author shouldn't significantly impact your belief in the conclusion (kind of like argument screens off authority), but that is true of tone arguments as well.
The justfication for placing tone above ad hominem in the hierarchy is that the former at least responds to the writing, not the writer. But surely this isn't adequate justification. One might respond to the writing in many ways that are entirely irrelevant to the disagreement, e.g. by reproducing the written piece in reverse order. The question should be, which of these responses is more often relevant to a proper assessment of the truth of the conclusion.
Like a well-motivated ad hominem attack pretty much boils down to an accusation of motivated cognition, a well-motivated attack on tone usually amounts to an accusation of bad faith. While that shouldn't affect your conclusion given a constant set of evidence, it can certainly change your or your audience's weighting of evidence presented and shape the way you approach it rhetorically: if you suspect your opponents might be trying to score political points rather than to present a coherent argument, it behooves you to be more careful in parsing their argu...
- Gandhi
Now that most communication is remote rather than face-to-face, people are comfortable disagreeing more often. How, then, can we disagree well? If the goal is intellectual progress, those who disagree should aim not for name-calling but for honest counterargument.
To be more specific, we might use a disagreement hierarchy. Below is the hierarchy proposed by Paul Graham (with DH7 added by Black Belt Bayesian).1
DH0: Name-Calling. The lowest form of disagreement, this ranges from "u r fag!!!" to "He’s just a troll" to "The author is a self-important dilettante."
DH1: Ad Hominem. An ad hominem ('against the man') argument won’t refute the original claim, but it might at least be relevant. If a senator says we should raise the salary of senators, you might reply: "Of course he’d say that; he’s a senator." That might be relevant, but it doesn’t refute the original claim: "If there’s something wrong with the senator’s argument, you should say what it is; and if there isn’t, what difference does it make that he’s a senator?"
DH2: Responding to Tone. At this level we actually respond to the writing rather than the writer, but we're responding to tone rather than substance. For example: "It’s terrible how flippantly the author dimisses theology."
DH3: Contradiction. Graham writes: "In this stage we finally get responses to what was said, rather than how or by whom. The lowest form of response to an argument is simply to state the opposing case, with little or no supporting evidence." For example: "It’s terrible how flippantly the author dismisses theology. Theology is a legitimate inquiry into truth."
DH4: Counterargument. Finally, a form of disagreement that might persuade! Counterargument is "contradiction plus reasoning and/or evidence." Still, counterargument is often directed at a minor point, or turns out to be an example of two people talking past each other, as in the parable about a tree falling in the forest.
DH5: Refutation. In refutation, you quote (or paraphrase) a precise claim or argument by the author and explain why the claim is false, or why the argument doesn’t work. With refutation, you're sure to engage exactly what the author said, and offer a direct counterargument with evidence and reason.
DH6: Refuting the Central Point. Graham writes: "The force of a refutation depends on what you refute. The most powerful form of disagreement is to refute someone’s central point." A refutation of the central point may look like this: "The author’s central point appears to be X. For example, he writes 'blah blah blah.' He also writes 'blah blah.' But this is wrong, because (1) argument one, (2) argument two, and (3) argument three."
DH7: Improve the Argument, then Refute Its Central Point. Black Belt Bayesian writes: "If you’re interested in being on the right side of disputes, you will refute your opponents' arguments. But if you're interested in producing truth, you will fix your opponents' arguments for them. To win, you must fight not only the creature you encounter; you [also] must fight the most horrible thing that can be constructed from its corpse."2 Also see: The Least Convenient Possible World.
Having names for biases and fallacies can help us notice and correct them, and having labels for different kinds of disagreement can help us zoom in on the parts of a disagreement that matter.
Let me illustrate by labeling excerpts from Alvin Plantinga's critical review of Richard Dawkins' The God Delusion.
DH1, Ad Hominem:
DH2, Responding to Tone:
DH4, Counterargument:
DH6, Refuting the Central Point:
Of course, even a DH6 or DH7 disagreement can still be wrong. But at the very least, these labels can help us highlight the parts of a disagreement that matter for getting at the truth.
Also see: Causes of Disagreements.
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1 This article is an update to my earlier post on CSA.
2 Sometimes the term "steel man" is used to refer to a position's or argument's improved form. A straw man is a misrepresentation of someone's position or argument that is easy to defeat: a "steel man" is an improvement of someone's position or argument that is harder to defeat than their originally stated position or argument.
3 For an example of DH7 in action, see Wielenberg (2009). Wielenberg, an atheist, tries to fix the deficiencies of Dawkins' central argument for atheism, and then shows that even this improved argument does not succeed.