riddle - Youth is, Inevitably, the Nature of Yielding Adulthood. Nurture it Greatly

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...

Answer

This is the

yin-yang, or taijitu.

We are both black and white with two seeds, But they each can never be planted;

Obvious from the image: the 'seeds' are the smaller dots inside each section.

Through our swirl, philosophy proceeds, But our balance is taken for granted.

It's a philosophical swirl representing balance.

Our forces conflict with each other, For we echo the knave and the knight.

The yin and the yang are two opposing forces.

But we're compelled to exist as together; A shadow cannot exist without light.

One is white and the other is black, as mentioned in the first line.

And if you couldn't get it from any of that...

the title has weirdly capitalized words that spell out the answer for you.