So tell me what was before time? Was there darkness only, or is there light? Or nothing, neither of them? One can't exist without other one. Its actually simple. Imagine black and white on your paper, and you are ready to paint and make your move to create art, and the suddenly black mixed with white and what do we get? Grey! Yes well done..so we create another color from nothing just with mixing them togehter, something what supposed to be oposite side just like darkness and light, or just like Yin and Yang if you prefer.. and yet they didn't destroy each other they made another form, so you see answer is very simple. In the beginning of time darkness and light mixed, and they didn't destroy anything, it never was war in begging with two of them, its was pure art, pure balance and they create a life. Life we know today as Universe.