'''Negative implication''' is an underdeveloped concept of logic that the existence of +1, for example, implies the existence of -1. The existence of good implies the existence of [[evil]]implies the existence of good, as an other example. The existence of the seen (the [[material]]) implies the existence of the unseen. And so on.
Mathematicians did not widely accept the validity of negative numbers until the 1800s.<ref>http://www.answers.com/Q/In_what_century_were_negative_numbers_finally_accepted</ref>