Light is a common symbol of knowledge.
But not only a symbol, because the light really favors a great part of our perceptual knowledge, especially the visual perception.
In this case, it is presupposed the existence of the daylight. And our imagination readily associates any kind of knowledge with the experience of viewing different things in the daylight. The hope in discovering truths becomes a hope in arriving at a sort of daylight.
But the daylight itself is rarely questioned. If we do this, then we observe that it helps us to perceive, but also that its power to extend itself over a great number of things makes us to easily move our interest from a thing to another.
Thus, the daylight offers us a kind of knowledge which can easily to be forsaken for acquiring another one. And the previous knowledge is abandoned into the daylight with the thought that it can be offered to us again in the future.
The desire of knowing as in the daylight has the same feature. We want to acquire that type of knowledge which can be put out from us, because we have become tired of living with its shadow in our efforts for reaching it.
Meanwhile, there is the wish for knowledge as a light in the night. A nocturnal light always focuses on a limited number of things and it ceases only where the bearer of the source of light decides. Those who want such a kind of knowledge become its masters and they are responsible for its end. But because it is their knowledge, it lasts as long as they last. Thus, such knowledge cannot be really finished and it always seems to be incomplete. However, only the knowledge we fully posses is our knowledge.