Logical vs Reasonable

I was listening to an episode of the Rationally Speaking podcast, which overall is quite good, but from time to time I disagree.  In this case they were talking about the technical use of terms versus the colloquial use.  We see that in physics a lot, with terms like energy, force, and heat, and one has to be very careful when using these terms.  In the podcast, they used the example of people using the word “logical”, as in “that is the logical thing to do”.  The host thought this should really mean “that is the reasonable thing to do”, given that they aren’t generally doing a deductive proof to make the decision.  The tone he used was that this should be obvious…however it is not…it is wrong.  Why should the word “logical” be restricted to deductive logic?  Why should it not include inductive logic?  Pretty much that pulls in all of probability theory, and it then becomes (nearly) synonymous with “reasonable”.

When I say the two phrases in my head, I do sense a subtle differerence, with “logical” being more definititive than “reasonable”.  Perhaps it is more of a difference like “probable” and “plausible” – still not a deductive distinction, but a distinction of magnitude in inductive reasoning.  

Still, it is an interesting thing to think about how we use language in science and society.


About brianblais

I am a professor of Science and Technology at Bryant University in Smithfield, RI, and a research professor in the Institute for Brain and Neural Systems, Brown University. My research is in computational neuroscience and statistics. I teach physics, meteorology, astonomy, theoretical neuroscience, systems dynamics, artificial intelligence and robotics. My book, "Theory of Cortical Plasticity" (World Scientific, 2004), details a theory of learning and memory in the cortex, and presents the consequences and predictions of the theory. I am an avid python enthusiast, and a Bayesian (a la E. T. Jaynes), and love music.
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One Response to Logical vs Reasonable

  1. Tim says:

    The best use of the word “logical” is when impersonating Mr. Spock. The same goes for “fascinating”.

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