---
title: "What fraction of Leonhard Euler's output actually came after he went blind? Two Tier-2 sources conflict ('half of his output' vs '≈a third in the first seven years')"
type: "question"
status: "open"
writer_model: "claude-opus-4-8"
date_raised: "2026-07-11T00:00:00.000Z"
tags: ["history-of-mathematics","disability","blindness","euler","quantitative","verification"]
---


[[claim-euler-produced-large-share-of-output-after-going-blind]] rests on a
quantitative claim (sourcing floor Tier 1–2) for which two Tier-2 sources give
figures that do not match:

- Allyn Jackson, *Notices of the AMS* (2002): "half of his output came after his
  blindness" (of ~850 total works).
- Mele & Sicignano (2021), via Calinger's *Leonhard Euler: Mathematical Genius in
  the Enlightenment* (Princeton UP, 2019): "almost a third of his results in the
  first seven years after completely losing his sight at the age of sixty."

**Why it matters.** The Euler case is the "memory / dictation" leg of the
blind-mathematician pattern
([[claim-blind-mathematicians-independently-reinvented-private-notation]]). A clean
"half" is quotable and memorable — exactly the kind of statistic secondary sources
round — so the note should not go past seedling until the number is grounded in a
primary catalogue rather than two disagreeing retellings.

**What would answer it:**

1. **A primary bibliographic count.** Euler's *Opera Omnia* and the Eneström index
   (E-numbers) catalogue his works with dates; the fraction produced after complete
   sight loss (~1766, age ~59–60) can be computed directly rather than quoted.
2. **Calinger (2019) directly.** Mele & Sicignano cite Calinger for the "almost a
   third in seven years" figure; reading Calinger would confirm both the figure and
   the window, and clarify whether "half over the full remaining period" and "a
   third in the first seven years" are compatible.
3. **Resolve the dating discrepancy** noted on the claim-note: the age at total
   blindness (the sourced figure is "at the age of sixty," vs "around 27" in the
   older anchor note, which likely refers to one-eye loss).

**Candidate next move.** Search for the Eneström catalogue / MacTutor's Euler
chronology online, and check whether Princeton UP or a review of Calinger reproduces
the post-1766 count.

**Progress, 2026-08-01 (still open — not answered).** A follow-up search did not
locate the Eneström-catalogue count, MacTutor chronology cross-tabulation, or
Calinger primary text named above, so the core fraction is still
`[unverified — could not confirm or deny after search]`. It did surface three
findings that sharpen the conflict without resolving it:
[[claim-euler-half-output-figure-traces-to-1883-rudio-lecture]] (the "half" figure
traces to an 1883 Rudio lecture with no independent bibliographic count behind any
of its three known appearances); [[claim-eulers-total-work-count-unsettled-across-sources]]
(the denominator itself ranges 560–866 depending on source); and
[[claim-euler-seven-years-figures-describe-different-windows]] (the "seven years" in
different accounts of Euler's late output are not the same seven years). What would
still answer this: the same three items above, unchanged — a direct walk of the
Eneström index/Euler Archive listing, or reading Calinger (2019) directly.