A little googling reveals that Simplex sigillum veri—"Simplicity is the seal of truth" or "The simple is the mark of the true"—is best known as the motto of Dutch physician Hermannus Boerhaave (1668–1738).* I haven't come across anything suggesting that the doctor coined the phrase himself, though, and I'm wondering how and when it arose.
In particular, when did the maxim originate and what kind of observation is it meant to summarize? That is, of what line of thought is it the conclusion? Or in other words, what does it mean?
The thought seems to attract immediate dissent, as most philosophical propositions do. It's easy to think of simplistic ideas whose falsity is suggested by their extreme simplicity. Consider any sentence beginning with "The cause of all disease is…" Medicine, especially, seems like a field teeming with counterexamples.
I think there must be some important truth in the maxim. Perhaps understanding its origin might shed light on it. I first encountered Simplex sigillum veri in this passage by the mathematician G. Polya, coming after noting some strikingly simple patterns in the center of gravity of three shapes, suggesting generalization:
It appears extremely unlikely that the conjectures suggested by these questions should be wrong, that such a beautiful regularity should be spoiled. The feeling that harmonious simple order cannot be deceitful guides the discoverer both in the mathematical and in the other sciences, and is expressed by the Latin saying: simplex sigillum veri (simplicity is the seal of truth).†
Prof. Polya seems to have picked up the maxim from some long-running tradition. That's what I want to know about.
*Alas, one historian reports that Dr. Boerhaave preached the motto more than he practiced it.
†How to Solve It (1945), p. 45.
