A Pinprick of Light
If you were in the deepest reaches of space, engulfed in millions of cubic miles of darkness, a pinprick of light would still penetrate it. It could not be extinguished by any quantity of darkness.
Light can disperse darkness but not the other way around. Light can also spread. Fire lights other fires, a beam can bounce and reflect off of other objects. Darkness cannot reproduce itself, it can only occupy space left behind by vacating light. It is a borrower, a usurper, not a creator. Light has a source, darkness is devoid of source; it is the absence of source.
Darkness is always lurking, ready to overtake any place where light goes out. When times seem darkest it’s not because darkness has increased, but because lights have grown dimmer.
That’s good news. It means every time you are the tiniest light, you are reducing the darkness. It can be beat back, but only as light increases.