Content-type: text/html ~ Stephen's Web ~ Making Up Facts

Stephen Downes

Knowledge, Learning, Community

Sept 29, 2009

Originally posted on Half an Hour, September 29, 2009.

I think I'll stop reading Willingham if he persists in making stuff up.

He writes, "Prior knowledge is vital to comprehension because writers omit information. For example, suppose you read “He just got a new puppy. His landlord is angry.” You easily understand the logical connection between those sentences because you know things about puppies."

It is no such thing. The two sentences have the form of an explanation. The landlord is angry [because] he got a new puppy. Nothing should be inferred regarding the cause of the landlord's anger: it may easily be allergies, dislike of yapping dogs, town bylaws about animals, or blind prejudice. And inference that involves the putative 'knowledge' about puppies would be an error.

In fact, the inference as to the structure of the explanation is based on a much more general inference, the observation that one statement is propositional (a 'fact') and the other expresses an attitude (an 'emotion'), and while facts explain emotions, emotions do not (generally) explain facts (though an _honest_ reader would leave open that he purchased the puppy in retaliation for the landlord's persistent and unreasonable anger).

Appealing to 'facts', especially when you're just making them up, leads to terrible reasoning, and even worse educational theory.

And let me add a point to this...

Willingham frequently makes this sort of appeal, where the reader is supposed to come to some sort of understanding based on a recollection of relevant (domain-specific) facts.

In logic, this sort of form is known as the 'implicit premise'. "Don't play in traffic. It's too dangerous," says the mother. You are supposed to know that traffic is dangerous, or that you should avoid dangerous things, or some such thing.

But - and this is the key point - implicit premises are filled not by domain-specific knowledge, but rather, by logical form. When reading the passage, the reader employs what is known as the 'principle of charity', which is, to infer that the writer means to state the premise or premises that would make the inference sound.

"Don't P. P is Q." Implicitly, "Don't Q". Because that is what makes the inference reasonable. What is "Don't Q"? Much as Willingham wants it to be, it is not domain knowledge. It is an inference, generated by the charitable reader, who has a good understanding of reasoning, and needs no particular understanding of the domain.

Of course, Willingham disguises this, by abducting, instead of the reasonable implicit premise, some domain-specific information that sometimes does and sometimes (as in this case) does not have anything to do with the inference. It's a sleight of hand. If the interpretations appear reasonable to you, it's not because you have domain knowledge (though he always keeps his examples simple, to foster the illusion), it's because you recognize the logical form of the argument.

It's a tired old trick and I wish Willingham would quit doing it and try some real psychology, or pedagogy, or whatever it is that he's doing.

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Stephen Downes Stephen Downes, Casselman, Canada

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