A man and woman sit aboard a boat in a dark ocean headed toward land. The porcelain colored city in the distance is bathed in a soft light. It is close enough to be real to them, but distant enough for the atmosphere to make it dreamy and insubstantial.
Look at how the man's jacket ripples as though he were a continuation of the sea. To his darkness (tonally and metaphorically), the woman is the light. He is one with the dark forbidding sea; she, her dress the color of clay, represents land and home and safety on a solid earth. She is perched up hopefully. The man, with slumped but straightening shoulders, looks up at land with similar longing, but as though as at a hope that is less real to him. This dynamic between the characters tells us that she is the greater moral strength between the two. The fact that she is in the light while the man is in shadow tells us that her strength has some connection to the illumination in the sky.
The light in the clouds sits somewhere between the boat and the city. Many artists have used sunlight as a symbol for hope and the dawning future, but Friedrich uses it in a special way. A typical artist might have placed it directly behind the city, connoting a glowing evanescent heaven. By putting the light between the foreground and background, Friedrich suggests that this light is moving ahead of the ship and pulling it along. Friedrich, himself a deeply religious man, might have considered this the light of God reigning over the sea and land, lending a beacon to those who venture too boldly into his creation. Abstracting from the specifically Christian interpretation of this element, we can view it as a kind of will, or living intelligence inherent in nature. A will which precedes and guides our own.
Friedrich communicates a tremendous wealth of information through this composition—much more than I have mentioned here—and everything he says is in the concretes of the painting. This is not an illustration of something we already knew, it does not require previous knowledge or even an explanation. We see the lesson that the artist is teaching us. We see it in those attributes that he has isolated in his portrayal, and these attributes are stressed by the absence of all the thousands of attributes a scene such as this might possess in real life, but which Friedrich has chosen to omit. As Ayn Rand said in "Art and Sense of Life,"
[An artist] selects those aspects of existence which he regards as metaphysically significant—and by isolating and stressing them, by omitting the insignificant and accidental, he presents his view of existence. His concepts are not divorced from the facts of reality—they are concepts which integrate the facts and his metaphysical evaluation of the facts. His selection constitutes his evaluation. . .
There have been very few artists in history who live up to the role that Ayn Rand was describing in this quote, very few men who relied on nothing but the picture they created to communicate that picture's meaning. This principle, which Ayn Rand did not identify until the 20th Century, was a central aspect of an art movement that was born at the end of the 18th. The school was Romanticism, and Friedrich was among its most towering figures.
I would like to add as a purely personal note that I love this painting. I don't agree with its religious premise, but as an integration of thought and image, it is just simply a marvel to behold. Its colors and brushstrokes especially are a feast for the eyes. Notice how the blues and greens of the sea seem to "float" on the underpainting of brown. See the almost melodic harmony of the brown, gold and green in the mast and sail, and how the sequence of vertical lines that compose these objects provide a rhythm that send your eye flying into the sky. The brushstrokes of the sky are each a distinct mark and they radiate out in a concentric ripple. The texture created here is unusual, and resembles the inconsistent nap of a carpet. This gives the spread of clouds a realness, a stressed physicalness that unites them with the sea below and further concretizes Friedrich's metaphysics—specifically his feeling that all of the world is an integrated unity, that spirit and nature are one. True, Friedrich believed in God, but a God that is in Nature, not beyond it.