The question of how to measure the “effect” of rhetoric is one of the most difficult problems in rhetorical theory. I consider it practically unsolvable. How can you reliably point to a specific instance of speech and connect it to a specific effect?
Simple interactions are of no practical difficulty, of course. If I tell my 8-year-old son to get dressed for school and he immediately does so, we might assume, reasonably, that my request triggered his action, absent some other unstated context. But few would dispute such a conclusion, and it’s only the conclusions that are under dispute that are generally worth talking about.
For example, some time ago in this space, I discussed a striking speech by President Biden. Since then, the Democrats had a strong midterm, by any historical or contemporary measure; they still have Senate control and the GOP has a slim and unstable majority in the House. The question of effect thus comes into play here: did Biden’s aggressive stance toward MAGA Republicans in the speech bring about that outcome?
Now, I should be clear, I don’t think this question can be answered, at least in any authoritative way. Rather, I’m interested in discussing how this case can render the complicated nature of all rhetorical utterances. Perhaps a medium-size case, rather than a huge one, might help illustrate my larger point.
Imagine Biden stumping across Iowa in the 2024 presidential election to come. He enters a diner for the usual lunch and photo opportunity. Suddenly one of the customers begins to choke on a chicken bone, and Biden promptly executes the Heimlich maneuver. The bone dislodges. The man is saved. An impromptu video makes the social media rounds to acclaim. Later on, he wins the state primary handily. Did this incident win him the state?
Maybe. Maybe not. Simple cause-and-effect chains are appealing, of course. Aristotle was dead-on about the centrality and power of the enthymeme. But the absence of a warrant – or, rather, the implication of one, to be filled in by the listener – allows a rhetor to avoid the responsibility and risk of making a direct connection between one event and another. Most of the time, therefore, the tactical dodge that an enthymeme allows is a sound plan. I wish Toulmin had discussed this more, as he offloads most of rhetorical evasion to modals.
The problem of induction, usually as formulated by David Hume, is related, though the P of I is far more epic in scope and character. No future event can be guaranteed based on analysis of past events, according to Hume, including relatively straightforward stuff like the sun rising in the morning or your death after falling from the Empire State building. Something else can always happen or intervene – the classic black swan, perhaps, will consume the sun, or swoop past and catch you.
The problem of rhetoric and effect, therefore, is the problem of induction in reverse. Instead of future events being impossible to logically guarantee, past events that might seem to be in a cause and effect relationship with later ones cannot be conclusively linked. We can only argue for a connection between a possible cause and a possible effect. Rhetoric is therefore a hack that makes decision-making between humans possible. Acknowledging the impossibility of “proving” the warrant is generally considered a weakness and a vulnerability (“That’s just a theory!”) but I consider such a realization of the limits of human knowledge to be the absolute bedrock of intellectual inquiry.