Evil: the privation of a good that should be present. It is the lack of a good that essentially belongs to a nature; the absence of a good that is natural and due to a being. Evil is therefore the absence of what ought to be there.

https://www.catholicculture.org/culture/library/dictionary/i...

https://en.m.wikisource.org/wiki/Catholic_Encyclopedia_(1913...

The constructivist in me thinks we could define it inductively :)

How about: skeptical of formal verification?