The darker the shaw, the brighter is the light

We cannot know that we are illuminated by a great light simply by looking up into the sky. But if we lower our heads and look down at our feet, we can clearly see the long, dark shadow that stretches out from us. We know that the darker and blacker that shadow is, the brighter is the light that shines upon us. Thus, we have been told to look at our own dark shadows [within].