It seems I have done something to my WordPress installation, and for some reason it can’t find my posts, though they do appear on the “home” page.

I have temporarily fixed it by changing the theme, so that the whole post shows on the home page instead of just the excerpt, but the posts are still not visible on their own pages.  Please be patient until I fix the issue, and until then, the full posts are on the main page.

Thank you to the people who brought the issue to my attention!