How does to know better than to do <something> effect/imply/induce the definition:
Please explain the steps, thought processes; I’d like to try to resolve this myself in the future? I realise that this may seem a basic question, but I want to confirm because the definition above connotes positivity, whereas this use by the Spectator alludes to slyness?
This idiom first shows up in the 1680s, and at that time it has two forms:
A. the modern version know better than to, and
B. a fuller version know better things than to.
A and B trot along side-by-side for about a hundred years, but towards the end of the 18th century B drifts out of use.
The idiom is founded on long established expressions (they go back at least to Chaucer):
know [something] better than [something else], meaning to be aware of something which is better than something else
know [something] better than [someone else], meaning to be more knowledgeable about something than someone else is.
The B version obviously has sense 1: know things to do which are better than what you are doing or proposing to do. I would guess the A version to have been originally just a shorter version of the B version, with better understood as a nominal something better. But I suspect it finally superseded B because it also accommodated understanding in sense 2: you are too knowledgeable to do what you are doing or proposing to do