Dinosaurs and inference rebuttals

Spotted at the Creation Museum:

Q: Are human bones found with dinosaur fossils?

A: None have been discovered yet.  However, if human bones aren’t found with dinosaur bones, it simply means they weren’t buried together.  Humans have come in contact with lots of animals, like crocodiles and coelecanths, but they aren’t buried with humans.

The obvious thing to say about this is that it is flagrant “confirmation bias” – seeking or treating evidence in such a way as to confirm one’s cherished beliefs rather than to evaluate or test them.

From an argument analysis perspective, though, it is a nice example of what, technically, we’d call an “inference rebuttal” – an objection to an primary objection which targets not any of the stated premises of the primary objection but rather the inference from the primary objection to the falsity of the main contention.

That’s quite a mouthful, but the basic idea is simple enough, and can be easily illustrated.

Doing so will help explain one of the most distinctive – but subtle – features of the Rationale software.

On the face of it, the fact that human bones have not been discovered with dinosaur fosils is an objection to the standard Creationist story, which includes the idea that humans and dinosaurs once both roamed the earth at the same time.

The premise of the objection is a blunt fact, and so the Creationist has to accept it:

However the Creationist still wants to defuse the objection, and can do it by arguing that the premise, though true, doesn’t show that the contention is false.

To represent this kind of move, Rationale allows a lower-level objection to be connected to the primary objection itself rather than to any of its premises.  Graphically, the lower-level objection points to the word “opposes”:

Evaluating this argument as a Creationist presumably would, the objection has been defused:

There is however another way to read the Creationist’s argument.  This way of framing things probably better reflects the Creationist’s underlying mindset.   From this perspective, creationist “science” combined with the basic facts imply an interesting “discovery”: those humans who did (supposedly) coexist with dinosaurs never buried themselves with said dinosaurs:

Why distinguish reasons and explanations?

A colleague wrote:

In both your new Rationale materials and your old Reason! lessons you distinguish between reasons and explanations. For instance, you point out that the word “because” is sometimes a reason indicator, other times an explanation indicator. I was wondering why, pedagogically, you make a point of distinguishing between arguments and explanations. You seem to want the students to focus primarily on the former and not the latter, but I anticipate that my students will find this confusing. I was wondering why, as a pedagogical matter, you point out this distinction to your students, and how you explain it to them.

My reply, such as it was:

I think that in the larger world of critical thinking, students should understand evidential reasons, and what makes them strong, and explanatory reasons, and when explanations are good ones. However when we are focusing on the former, the latter tends to muddy the waters.

Deanna Kuhn, in her classic The Skills of Argument, provides weighty evidence that a very large proportion of people have a seriously deficient grasp of the basic skills of reasoning and argument, and she diagnoses the problem as due in part to a poor grip on what a (evidential) reason is, i.e., what evidence consists in. Part of understanding this notion of an evidential relationship is understanding that sometimes, when we say things like the reason for X is Y, we’re not using Y to convince somebody that X is true, i.e., we’re using it to explain X rather than as evidence for X, which may already be uncontroversial.

There is now a considerable psychological literature on (evidential) reasons versus explanations. My take on this, which I think is broadly consistent with the literature, is that (causal) explanations come first. Our three-year-old seems to be getting a grasp of causal relations and answering “why” questions in terms of causal narratives, but she’s a long way from understanding the notion of evidence. The latter is a more sophisticated intellectual operation, one which only with considerable maturity is separated from explanations. A problem we face as university teachers is that our students haven’t fully made this transition; they are still foggy about the difference, which means they are foggy about the notion of evidence, which means they haven’t yet mastered the most fundamental concept in reasoning and argumentation.

You’ll notice that in Rationale, the second or “Reasoning” mode uses “because/but” language. This is ambiguous between explanations and evidential reasons. In the designing the software we were quite deliberately “allowing” that ambiguity, since it helps people who aren’t yet clear on the distinction become comfortable with structured reasoning on their own terms. As they progress to proper use of “Analysis” mode, with its language more weighted to the evidential (“supports”), they should be becoming more clear about what an evidential relationship consists in, not by being lectured on the topic (though that might sometimes help) but by dealing with examples in a scaffolded way.

By the way, Deanna Kuhn has an interesting piece on peoples’ ability to identify causal relationships in the current edition of Scientific American Mind.