I dreamed about the date 18.v.1638 (May 18, 1638) last night.

As I currently do research on odd perfect numbers, and because Rene Descartes lived during the years 1596 to 1650, and as I am not a math historian, I would like to ask the experts here:

Did Rene Descartes send or receive any letters (regarding mathematics) on 18.v.1638 (May 18, 1638)?

I tried searching via Google, using the keywords Descartes and 18.v.1638, but there are too many search results (with none of them promising). I did skim through a few of them, but did not find any letters on mathematics sent to or received by Descartes on May 18, 1638.

  • 1
    $\begingroup$ Electronic Enlightenment has a catalog of Descartes's letters. There are twenty from 1638, but none from May 18. However, there is one with uncertain April/May dating, and some dates were revised by editors after the discovery of his correspondence with Huygens senior, see EMLO. $\endgroup$
    – Conifold
    Aug 10, 2022 at 5:20

1 Answer 1


On checking the Early Modern Texts for Descartes' correspondences, I did not find any correspondence of Descartes dated precisely to 18.v.1638. However, Descartes sent a letter to Reneri which has been dated to April or May, 1638. Because of this ambiguous dating, it seems like we don't have the knowledge that if there was a correspondence precisely on 18.v.1638.


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