Speculative Evidence


The argument draws a conclusion form an assertion about what the evidence would show, if one were actually to look at it; however, the argument appeals to evidence that has not actually been collected or does not actually exist.




"The United States is getting further and further behind in science education. You probably couldn't find more than a handful of American high school students who could explain Newton's laws of motion to you."


"Men are just as emotionally sensitive as women. I'm sure that if you did a study you wouldn't find any statistical difference between men and women."


"You know, if you go back and look at everybody else's decisions, whether its a U.S. attorney, or an assistant attorney, or a judge, you go back twelve or fifteen years ago, or twenty years ago, and look at their past decisions, I would think you'd probably find that they would wish they'd maybe did (sic) it a different way." - Donald Trump, July 9, 2019, in an interview defending Labor Secretary Alex Acosta for failing to adequately prosecute multimillionaire Jeffrey Epstein for the sex trafficking of underage girls.



Of course there is nothing wrong with speculating on the anticipated results of an experiment or study. Indeed, speculation of this kind is precisely how experiments are conceived of and designed. In a careful experiment, it is even necessary to state the "experimental hypothesis," which is what we speculate will be the outcome of the experiment.

It is perhaps because good experimental design requires us to speculate that mere speculation can sometimes pass as genuine evidence. The fallacy of Speculative Evidence mimics good reasoning by correctly performing the first step in the design of an experiment, namely the stating of the anticipated results. However, the fallacy errs by then sneaking straight to the conclusion without actually performing the experiment, i.e. treating the anticipated results as if those results were already confirmed and could be relied upon.

In the example above, Donald Trump speculates that any prosecutor or judge will have regrets about the handling of his or her past cases. Perhaps this is true. We all have some regrets, so this seems like a reasonable hypothesis. But in order to determine that "every" judge or prosecutor has serious regrets about their handling of past cases, it would be necessary to ask them. A study might show that Trump's speculation is correct; but, a study might also show that his speculation is wrong. Since no such study has been conducted, we have no way of knowing whether Alex Acosta's behavior was typical (and therefore perhaps excusable) or untypical.

This seems like an obvious enough fallacy, so it is surprising how many people confess to being guilty of it. I first spotted the fallacy by observing my own tendency to treat my own speculations as if others should be convinced by them. There are many instances in which a presumed truth, held for long periods of time by many people, but backed up by nothing more than speculation about what evidence would (eventually) show, was proven false when a study was actually done. For example, I remember hearing recently of a wealthy philanthropist who had assumed--as do most people--that it is a waste to give substantial amounts of money directly to poor people, since they will only spend it on frivolities and then return to being poor. He decided to test this assumption by giving a couple thousand dollars to a few randomly selected poor people. To his surprise, many of them used the money to purchase tools, or means of transportation, which significantly improved their ability to make more money. This resulted in significant, long-term improvements in their lives. The charity proved to be highly cost-effective. This was not a scientific study, but we can speculate that direct, no-strings-attached assistance to the poor might significantly reduce poverty...if someone were to do a real study on the matter.


Source: I named this fallacy.


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