Just because we assume that something does not have an opposite does not make it true.... am I correct.... or are you willing to extrapolate that just because you do not know what the opposite of a square is or that you presume it nonexistent that opposition does not exist as a primary aspect of life???
Would you be willing to make the assumption that the oppositye fo a square indeed does not exist?? Can you say for sure that it is just possibly a geometric figure that does not exist which does so in absolute opposition of said square???
Mathematically the opposite of a square is indeed possible

A negative square if you would. Of course the math would be a headache

Or if you wanted to get real nit-picky you could suggest the triad belief in opposition and suggest that said square would not exist without its opposite poles or right-angles which give it the shape. In other words the whole is only made whole by two opposing forces.
Idealistically one could suggest that what makes humans whole is thier ability to exist with two opposing forces battling within them(good and evil--moral and immoral). With both we are whole--- at one extreme or the other you would no longer be "human".
The flaw is within our perceptions.