Riddle me this:
We are both black and white with two seeds,
But they each can never be planted;
Through our swirl, philosophy proceeds,
But our balance is taken for granted.
Our forces conflict with each other,
For we echo the knave and the knight.
But we're compelled to exist as together;
A shadow cannot exist without light.
What are we?
My previous riddle was too easy, so I am not giving out any hints, though I will say just one thing: the opposites in the title is not the only clue hidden there...