Yin and Yang.

“Yang is the initiating impulse, which divides and delineates; yin is the responsive impulse, which nurtures and reunites. Without yang nothing would come into being; without yin all that comes into being would die. Yang is mental activity in its forceful aspect, yin the imaginative and poetic, exalting the merely mental to the beautiful. Yang goes ahead with things, yin contains things within herself and knows their nature without effort. Yang does, yin is.”