The riddle of Light and dark

This morning I went for a walk through the forest. It rained last night and the roads were puddled but the air was fresh and the vegetation green. It was pleasant to walk briskly early after a long time.
Then I was thinking meditatively whether darkness was absence of light or whether light was absence of darkness and I remembered a discussion I had some years back with Anuradha Chaudhari, a young, bright, cheerful girl I know. She held that Light was the origin and the appearance of darkness was because of a certain withdrawal of light. She suggested that darkness was not real; it had no substance whereas light was substantial as well as real.
I was advocating the fundamentals of darkness as the basis upon which light shines. I held that darkness was the principle that gave validity to light as much as the other way around. "like a room" I argued, "that does not get lit until light is brought in it." Both were principal opposites at the root of  manifest nature according to me. 
But Anuradha refuted my argument saying that light was always present. That confining space by building walls caused withdrawal of light which, she said, was present there before that space was converted into a room.
We debated for some time inconclusively and then decided to talk of other things more mundane and manageable.
This morning while walking the whole thing came back and I saw the validity of choosing to be on the side of light as the principal factor. Given that our life on this planet is brief in which to act and achieve, it is better to side with light than darkness. Championing darkness is negative somehow. It leads to a certain denseness in our approach to living. Considering that this is inconclusive - considering that we live in light as well as dark - it is important that we consider the utility of either and determine which is more useful as far as "acting in order to achieve" something in a brief span of our life is concerned. I think that light is more beneficial and not darkness.
Symbolically used, both become metaphores for life and death and it is positively good to say YES to life than death.