Kuzari (1,57) uses the widely accepted 7-day week to prove that we all have a common ancestor.
I’m wondering if this might be a bit of a Sharpshooter’s fallacy on the part of the Kuzari. After all, he (and later people who make similar claims) can only say this because the seven day week has, indeed, won out and become the standard. If the nine day week (just to pick an example) had one out, they would make a similar claim.
The Wolf