Today, we watch a play within a play. The University of Houston's College of Engineering presents this series about the machines that make our civilization run, and the people whose ingenuity created them.

I'm on a computer bulletin board that deals with rare books. The postings lurch through a wild array of issues -- some serious, some frivolous. And they throw light on an old conflict.

People go at questions two ways. Some say, "Let's think about it." Others say, "Let's go and look." Given any question, a Platonist wants to think it over. An Aristotelian expects to find a body of external fact.

Questions are what electronic bulletin boards are all about. One person asks, ten people answer. As that happens, the Platonists gravitate toward speculation and possibilities. The Aristotelians want clear questions and hard answers.

Someone recently posted a question about a notation in an old book. A 16th-century author had identified himself as a "Beyder Artzeney Doctor." What did that mean?

Answers poured in from all over the world. People speculated about medieval German. Did Beyder mean "of the" or "both"? Did Artzeney mean "medicine," "doctor," or "art"? The smoke gradually cleared. It meant a doctor of two kinds of medicine, but what two kinds: surgical, homeopathic, iatrochemical?

So I printed out the whole conversation, all 32 pages. The Platonists had been in hog heaven. The Aristotelians were understandably fed up with all that speculation -- half of it wrong.

Now the crowning irony: The term "Beyder Artzeney Doctor" was first used by the 16th-century alchemist Paracelsus. Paracelsus thought and wrote like a Platonist, but he acted like an Aristotelian. He united the scholastic Platonist medicine of the Church with the empirical medicine of the barber surgeons.

His two medicines represented two wholly different means for seeking the truth. No one liked him for that. All through Central Europe they ran him out of towns for his trouble.

In perfect counterpoint, the Aristotelians on the rare book network rose up in anger. As the Beyder Artzeney discussion wound down, they erupted. " ... this subject has been exhausted," cried one. "How many rare book people does it take to screw in a German Phrase?" asked another.

So the Platonists shut up. Now they wait quietly for the next delicious question. And it will come. The fight will erupt again, just as it has been doing ever since Plato and Aristotle.

But while the acrimony subsides, we remind ourselves what the original "Doctor of Two Medicines," Paracelsus, knew: we have to unite contemplation with observation -- speculation with conclusion. We're out of balance without both. It really takes doctors of both kinds to create real answers for our complex questions.

I'm John Lienhard, at the University of Houston, where we're interested in the way inventive minds work.

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The electronic bulletin board is called ExLibris. It embodies a very high level of expertise in many things -- chemical processes to preserve leather and to make paper, the forensics of theft and forgery, the identification of anything ever printed, and so on.

The municipal physician at Augsburg made Paracelsus's claim official when he addressed him as "beider arznei doctor" [both kinds of medical doctor] in an introductory letter (Debus, A.G., The English Paracelsians. New York: Franklin Watts, Inc., 1965, p.43.) That was a different spelling but the same idea. Language was in considerable flux in those days.

For more on Paracelsus (from the Catholic Encyclopedia), see the website: https://www.newadvent.org/cathen/11468a.htm.