Nothing makes it easier to resist temptation than a proper bringing-up, a sound set of values — and witnesses.

Jones delivers a characteristic epigram: moral education and “sound values” are presented as the official reasons one resists temptation, but the punchline—“and witnesses”—adds a wry, cynical realism. The line suggests that social surveillance and the fear of being seen (and judged or punished) often do more to restrain wrongdoing than internal virtue alone. It also plays on the gap between professed morality and actual behavior: people like to credit character, upbringing, and principles, yet in practice external accountability can be the decisive factor. The humor depends on that sudden shift from lofty ethical language to the mundane deterrent of being observed.