NOTE: If you'd like to hear the theory of plogglies from the "professor at Iowa, who was teaching general semantics," here is a ".wav" file of the one-minute clip from one of Wendell Johnson's 1956 lectures.

Nicholas Johnson [NJ]:  Thank you, Dennis. I would like to preface my question with an anecdote.

A professor at Iowa, who was teaching general semantics, to explain the scientific method posited a theory of plogglies. This was during the time before ball point pens, when people still used wooden pencils and two otherwise  unexplained phenomena occurred. One was that all pencils seemed to be extremely short. The other was that all pencil sharpeners seemed to be filled with shavings.  And the explanation the theory offered, the theory of plogglies, was that these plogglies came out of the ground at night, entered homes and office buildings, and ran all the pencils through the pencil sharpeners. In the morning they disappeared into the ground and were never seen. They theory thereby explained two otherwise inexplicable phenomena.

The question based upon the anecdote is: What are some of the problems that you encounter as a scientist trying to do experimentation and come up with theories with regard to things that often cannot be seen and cannot be known aside from positing theories about otherwise inexplicable phenomenon?  How is that different from the kind of scientific research you do in a lab with a chemistry tube, or something else in physics where you can observe the phenomena?

[DR]:  Very eloquent question.

Professor Mary Hall Reno [MHR]:  OK. Well, you’re totally right that the important feature of the scientific method is that you test your theory. So the ploggly theory of the pencils, what the ploggly theorists would do is say, "OK, we can’t see the ploggies because it’s at night, but let’s see what else would be evidence that they’ve been here.  Is there some theory we could make that would have an additional prediction that we could test that would fit both the pencil phenomena as well as the sharpener phenomena, but would also have some prediction that could be tested?"

So, when neutrinos, for instance, were introduced in the 1930s, it was partly to explain observed phenomena, namely that there seemed to be energy and momentum disappearing.  We don’t like energy and momentum getting lost, so the postulate was there was a particle that was carrying it away and we just couldn’t see it.  Then the theory was built to make predictions. And those predictions included that you should be able to make beams of these particles, and those particles should then at a specific rate produce, for instance, electrons when they interact. Then you measure the electrons.

So, really it is the sum of the evidence that has given us the view of neutrinos, not a single, individual thing. It's a case of going back to the theory and saying, "Does what I’ve measured make sense compared to the theory or not?" There really is a test of the theory.

[NJ]:  Well, that’s excellent.  You know, I’ve always believed in neutrinos, even before I encountered your explanation, and I’ve always been a little skeptical about the plogglies. Now I understand much better and see that my instinct was sound, and I thank you very much.