Life depends on a beam of light

'I Am Legend' is a 2007 post-apocalyptic science fiction film directed by Francis Lawrence

In September 2012, after a lethal worldwide epidemic, Robert Neville (Will Smith) is left as the last healthy human in New York City.

Only 12 million people were naturally immune to the virus. The rest degenerated into bald, pale, aggressive beings referred to as 'Darkseekers', who hunted down the immune humans as prey. The 'Darkseekers' are so-called for hiding in buildings and dark places during the day due to a painful intolerance to UV radiation.

In this scene, the protagonist and his dog can escape from the 'Darkseekers' thanks to a beam of light that is like a barrier between them and the others.
But it's the sunset and the beam of light is getting smaller...

Lady in the dark

Our lady of the hospital

"Our lady of the hospital", by Harrison Millard (1830-1895), it's a song from American Civil War music (1861-1865).

The lady sitting in the dark between the hospital tents, is illuminated by the light of a lamp. The dark represents the sad days of the Civil War, the light and the lady simbolize the pity for the soldiers.

  She sits in our long dark ward
  By the light of a shaded lamp,
  No sound but the cry of relieving guard
  And the sentinels’ heavy tramp

  [...]

"Light am I: ah, that I were night!"

"The night song", from "Thus spoke Zarathustra", written by Friedrich Nietzsche (1883-1885), talks about the meaning of life trought the opposition between light and dark, but in this poetry, dark means life and light means death.

"Light am I: ah, that I were night! But it is my lonesomeness to be begirt with light!

Ah, that I were dark and nightly! How would I suck at the breasts of light!

And you yourselves would I bless, ye twinkling starlets and glow-worms aloft!--and would rejoice in the gifts of your light".

Heroes and....antiheroes

Raffaello Sanzio, "Saint Michael tramples Satan"

Louvre, Paris (1518)

Light and dark may be used as metaphors. Heroes and heroines dress in light colors, bad figures are related to dark elements.

Allegory of the Cave

In the seventh book from "The republic" (514 b - 520 a), Plato illustrates "our nature in its education and want of education", trought the Allegory of the Cave. This relates to the idea of forms as people struggle to see the reality beyond illusion.

After "returning from divine contemplations to human evils", a man "is graceless and looks quite ridiculous when – with his sight still dim and before he has gotten sufficiently accustomed to the surrounding darkness – he is compelled in courtrooms or elsewhere to contend about the shadows of justice or the representations of which they are the shadows, and to dispute about the way these things are understood by men who have never seen justice itself?" (517d-e)

"The night is long which never finds the day"

John Singer Sargent, "Ellen Terry in the role of Lady Macbeth" (detail), 1889Tate, London

Metaphors of light and darkness are used in Macbeth by William Shakespeare to illustrate important themes such as evil and dishonest gain.

For example, Shakespeare uses the metaphor of darkness to illustrate Macbeth's slide towards depravity. He cannot face his deeds but needs the dark to hide what he is doing:

  Stars, hide your fires

  Let not light see my black and deep desires

  (i.iv.50-51)

The 'Force' and the dark side

In the epic space opera 'Star wars' (first movie in 1977) light and dark symbolize the contrast between good and evil. 

One of the prominent elements of Star Wars is the 'Force', an omnipresent energy that can be harnessed by those with that ability. It is described in the first produced film as 'an energy field created by all living things [that] surrounds us, penetrates us, [and] binds the galaxy together'.

The Force allows users to perform a variety of supernatural feats (such astelekinesis, clairvoyance, precognition, and mind control) and also can amplify certain physical traits, such as speed and reflexes; these abilities vary between characters and can be improved through training.

While the Force can be used for good, it has a dark side that, when pursued, imbues users with hatred, aggression, and malevolence.