I am not sure if I said something really stupid in response to this question
dunno if it would be a typo (I tend to think of them as identical) or a moment's confusion. Anyway, can someone post the comment I deleted?
It may seem a bit OCD to care! But I'm curious if I got that confused, and cannot recall.
I think I recall saying they were opposites but said the same thing, which is confusing, unless I commented that they express necessity and an inverse sufficiency.
Sorry for the OCD request, but I'd appreciate a copy and paste!
I've proven to myself that I don't tend to make that mistake, but I'm still intrigued. Anyway, not made to feel very welcome, so I'll delete again.