Like the Yen and the Yang

Without Winter, there would be no Summer.
Without night, there would not be day.
Without darkness, there would not be light.
I pondered this thought deeply one day last week, as I was gazing at the moon. I remembered that the moon could not shine upon us if it weren't for the sun, shining upon it. Really, the moon is just shining the sun back on us. So, without the sun, the moon would not shine its face down upon us. They work in harmony. Each planet needs each other in some way: if not for warmth and light, then for balance and support.

In this way, they remind me of the Yen and the Yang: two integral parts that make up our night and our day.

Without death, there would be no life.
Is this statement true? If it is, it lends a most intriguing idea to my mind to ponder. Does this mean that, perhaps, there could be more spirit, life... soul.. within some people than in others? Or is it perhaps an endless, or overly abundant, resource?
If this was true, it would explain to me why I feel like so many people are so... well, mundane, if you will. One of the things I am working on is to try and feel more connected with such people, and perhaps to discover why I feel this way. Perhaps this is it. I'm not sure, but it's one theory.