THE LAWS OF SYNTHESIS AND POLARITY

[beavis]

Synthesis
combine: Catholic priest and LSD (you could say they're opposites)
and you get: why the priest really thinks you're going to hell

[Tisha]

The Law of Synthesis, or the Union of Opposites, states that the synthesis of two opposing ideas will produce a third idea that is more true than either of the first two.

The Law of Polarity is closely related.  It states that anything can be split into two completely opposite characteristics, and that each of these polarities contains the essence of the other.
Think of the symbol of the Tao!  The blackness in white, the whiteness in black.  

The understanding of these two laws will cause a practitioner to abandon any and all fantasies about "white" and "black" magic.