The people walking in darkness
    have seen a great light;
on those living in the land of deep darkness
    a light has dawned.
~Isaiah 9:2

Advent is the season that, when properly understood, does not flinch from the darkness that stalks us all in this world. Advent begins in the dark and moves toward the light—but the season should not move too quickly or too glibly, lest we fail to acknowledge the depth of the darkness.

As our Lord Jesus tells us, unless we see the light of God clearly, what we call light is actually darkness: “how great is that darkness!” (Matt. 6:23).

Advent bids us take a fearless inventory of the darkness: the darkness without and the darkness within.

Advent is designed to show that the meaning of Christmas is diminished to the vanishing point if we are not willing to take a fearless inventory of the darkness.
~Fleming Rutledge from Advent- The Once & Future Coming of Jesus Christ

It is this great absence
that is like a presence, that compels
me to address it without hope
of a reply. It is a room I enter

from which someone has just
gone, the vestibule for the arrival
of one who has not yet come. 
I modernise the anachronism

of my language, but he is no more here
than before. Genes and molecules
have no more power to call
him up than the incense of the Hebrews

at their altars. My equations fail
as my words do. What resources have I
other than the emptiness without him of my whole
being, a vacuum he may not abhor?
~R.S. Thomas “The Absence”

There is no light in the incarnation
without witnessing the empty darkness
that precedes His arrival;
His reason for crossing the threshold into our world
is to fill our increasing spiritual void,
our hollow hearts,
our growing deficit of hope and faith.

God abhors a vacuum.

We find our God most when
we keenly feel His absence,
hearing no reply to our prayers,
our faith shaken, not knowing if such
unanswered prayers are heard.

In response, He answers.
He comes to walk beside us.
He comes to be present among us,
to ransom us from our self-captivity
by offering up Himself instead.

He fills the vacuum completely and forever.

In der Christnacht Lyrics and translation below

Dies ist die Nacht, da mir erschienen
des großen Gottes Freundlichkeit!
Das Kind, dem alle Engel dienen
bringt Licht in meine Dunkelheit,
und dieses Welt- und Himmelslicht
weicht hundert-tausend Sonnen nicht!

Lass dich erleuchten, meine Seele,
versäume nicht den Gnadenschein!
Der Glanz in dieser kleinen Höhle
dringt bald in alle Welt hinein,
er treibet weg der Hölle Macht,
der Sünden und des Todes Nacht!

On Christmas Night translation

This is the night on which I saw
the kindness of the Almighty power:
the Child whom all the angels serve
brought light into my darkest hour –
the light of heaven that yields to none:
not even a hundred thousand suns.

Let it illumine thee, my soul,
and shy not from its grace; so bright
the radiance from this cave, it soon
will fill the very earth with light,
will chase the powers of hell away,
and sin, and turn death’s night to day.