Of course, we have some voluntary control over whether and when we are prone to mistakes, so we can obviously have duties not to do thing that increase the likelihood of making them.

Surely this depends on the activity in which you might make the mistake. If you are working as an air traffic controller, it could be argued that you are presumed to have a duty not to make a mistake, since if you are discovered to have made a serious one, you will almost certainly be deprived of the opportunity to continue working as an air traffic controller.

In contrast, if you are working as a moral philosopher, it might be argued that you have a duty to make mistakes, so as to provide your fellow moral philosophers with continued gainful employment in discussing them. It’s a vexed area.

JP Stormcrow’s version of the story is much funnier.

The premise of the joke is that the professor was lecturing on duty and failed to be dutiful, isn’t that right? but his failure was not one of dutifulness (grammar!?), if I read it correctly. He missed his own lecture because of a confusion over dates and was mortified, according to the article, when he found out what he’d done.

If he’d been at the pub in the full knowledge of his dereliction, and hadn’t regretted his action, then I would agree his action was undutiful, but as it is it was something else. Forgetfulness, or poor calendar reading skills. I’m not sure. But I think the deliberate setting of his gaffe against the content of his lecture is a bit of long-bow-drawing by a subeditor in need of an amusing angle.

Reminds me of this bit from Toads by Philip Larkin :

Why should I let the toad work
Squat on my life?
Can’t I use my wit as a pitchfork
And drive the brute off?

Six days of the week it soils
With its sickening poison – Just for paying a few bills!
That’s out of proportion.

I think this proves my point.