"Dixitque Deus: Fiat lux. Et facta est lux. Et vidit Deus lucem quod esset bona: et divisit lucem a tenebris." -Genesis 1:3-4
Light seems to straddle to line between matter and energy. On the quantum level, light is made up of photons, or distinct "packets" of energy, which behave both as a particle and as a wave. Having properties of both matter and energy, light becomes a very vibrant symbol of spirit, and of the truths that are communicated spiritually.
To the naked eye, light appears to be pure energy. discrete amounts of light cannot be seen, but its effects can. It penetrates the darkness and, reflecting off the objects there, makes them perceptible to us. The light does not make the objects exist, of course, - if such were the case we wouldn't have to worry about stubbing our toes when we try to find our way to the bathroom in the middle of the night - but by the light we perceive them with our most refined sense; sight. John describes spirit as being of a similar nature: "The wind bloweth where it listeth, and thou hearest the sound
thereof, but canst not tell whence it cometh, and whither it goeth: so
is every one that is born of the Spirit." Though the spirit is not visible, in and of itself, its effect is. As the light of candles about the altar illuminate the lodge room, we are reminded that the Word of God also proceeds from the same place to illuminate and warm the soul.
Isaac Newton postulated that matter and energy are interchangeable, and the nature of light hints at this. Because of the nature of photons, light behaves both as matter and as energy. Thomas Young's double slit experiment shows that when light is shot at a screen with two slits in it, the light acts as as if it were a wave of energy, even when displaying attributes of a particle. More recent experiments of this nature have shown other particles to exhibit wave-like properties, even quite large molecules like buckyballs. If we extrapolate this information to a larger scale, we could theoretically say that all things can behave both as matter and energy. In this regard, we could say that light is just refined matter.
This is where another symbolic aspect of light comes into play. The duality of light shows us that we contain our own duality: Matter and Spirit. "There is no such thing as immaterial matter. All spirit is matter, but
it is more fine or pure, and can only be discerned by purer eyes; we
cannot see it; but when our bodies are purified we shall see that it is
all matter." (J. Smith) Light reminds us that as course matter may be refined into light, so too our course beings may be refined to a higher spiritual nature.
Yet another profound aspect of light is its influence on darkness. It is well known that one candle can vanquish much darkness, but that all the darkness in the world can never conquer, or even diminish the light of that candle. This is because darkness has no existence; it is simply Lack. So too, ignorance is is a void of truth, knowledge, and light:
"'They are Man's,' said the Spirit, looking down upon them. 'And they cling to me, appealing from their fathers. This boy is Ignorance. This girl is Want. Beware them both, and all of their degree, but most of all beware this boy, for on his brow I see that written which is Doom, unless the writing be erased. Deny it.' cried the Spirit, stretching out its hand towards the city. 'Slander those who tell it ye. Admit it for your factious purposes, and make it worse. And abide the end.'" (C. Dickens)
As the light erases the pernicious dark, so too we should first fill ourselves with light and knowledge, banishing our internal personal darkness, and then go out and spread the light of truth to fill the world.