How to Spot a Weak Argument

Daniel Dennett on the “surely” operator

W. W. Norton & Company
Science and Technology


When you’re reading or skimming argumentative essays, especially by philosophers, here is a quick trick that may save you much time and effort, especially in this age of simple searching by computer: look for “surely” in the document, and check each occurrence. Not always, not even most of the time, but often the word “surely” is as good as a blinking light locating a weak point in the argument. Why? Because it marks the very edge of what the author is actually sure about and hopes readers will also be sure about. (If the author were really sure all the readers would agree, it wouldn’t be worth mentioning.) Being at the edge, the author has had to make a judgment call about whether or not to attempt to demonstrate the point at issue, or provide evidence for it, and—because life is short—has decided in favor of bald assertion, with the presumably well-grounded anticipation of agreement. Just the sort of place to find an ill-examined “truism” that isn’t true!

“The word ‘surely’ is as good as a blinking light locating a weak point in the argument.”

I first noticed this useful role of “surely” when commenting on an essay by Ned Block (1994), which included several prime examples directed against my theory of consciousness. Here’s one, conveniently italicized by Block to emphasize its obviousness typographically:

But surely it is nothing other than a biological fact about people—not a cultural construction—that some brain representations persevere enough to affect memory, control behavior, etc. [p. 27]

This is meant to dismiss—without argument—my theory of human consciousness as something that must, in effect, be learned, a set of cognitive micro-habits that are not guaranteed to be present at birth. “Wherever Block says ‘Surely,’ ” I said, “look for what we might call a mental block” (Dennett, 1994a, p. 549). Block is one of the most profligate abusers of the “surely” operator among philosophers, but others routinely rely on it, and every time they do, a little alarm bell should ring. “Here is where the unintended sleight-of-hand happens, whisking the false premise by the censors with a nudge and a wink” (Dennett, 2007b, p. 252).

“A little alarm bell should ring.”

I decided recently to test my hunch about “surely” a bit more systematically. I went through dozens of papers—about sixty—on the philosophy of mind at and checked for occurrences of “surely.” Most papers did not use the word at all. In those that did use it (between one and five times in the sample I checked), most instances were clearly innocent; a few were, well, arguable; and there were six instances where the alarm bell sounded loud and clear (for me). Of course others might have a very different threshold for obviousness, which is why I didn’t bother tabulating my “data” in this informal experiment. I encourage doubters to conduct their own surveys and see what they find.

An excerpt from Intuition Pumps and Other Tools for Thinking by Daniel C. Dennett published by W. W. Norton & Company.

Buy Intuition Pumps and Other Tools for Thinking:

Amazon | Barnes & Noble | iBookstore | Indiebound | Powell’s

PS - don’t miss the Richard Dawkins live-tweeting of Daniel Dennett’s book collected on Storify.

Daniel C. Dennett (@danieldennett) is the Austin B. Fletcher Professor of Philosophy at Tufts University and the author of numerous books including Breaking the Spell, Darwin’s Dangerous Idea, and Consciousness Explained.