Despite the complicated plot and the numerous philosophical and literary digressions, a single main theme is evident throughout both parts of Faust and provides a unifying structure for the entire work. This is Faust's dissatisfaction with the finite limits on man's potential — the driving force that motivates him in all his adventures as he strives to find a way to pass beyond the boundaries set on human experience and perception.
The whole poem is colored by this sense of dissatisfaction and frustrated striving although its character changes as the story progresses. At the beginning Faust is in a state of negative dissatisfaction, in which he contemplates suicide and willingly accepts the terms of a pact that would terminate his life at its highest point of achievement. Further on in the poem Faust's dissatisfaction becomes a positive dynamic force that leads him eventually to find a form of personal fulfillment, but his whole life is marked by disappointment since he does not achieve peace of mind before his death, except in an inspired vision of the future.
Closely related to this theme is another one that is first established in the conversation between the Lord and Mephistopheles in the "Prologue in Heaven," and which is indirectly referred to at other points in the poem. The Lord acknowledges to Mephisto that it is natural for man to fall into error, but asserts that despite this he remains able to make moral distinctions. Thus the issue at stake in the wager made by God and the devil is whether Faust, as a representative of all mankind, will continue to be able to perceive the difference between good and evil, regardless of temptation and personal sinfulness. In the Lord's view of human nature, it is admitted that man is imperfect and that his ability is limited, but it is also assumed that human imperfection is not absolute and that man's potential for good can be cultivated. In this sense Faust's dissatisfaction and striving may be interpreted as an unconscious manifestation of man's potential to improve himself, even though Faust is frequently misguided by his obsessive efforts to rise beyond man's natural sphere. It is because Faust does retain his sense of right and wrong, and because his eyes are constantly focused on a vision of something higher than himself, which is ultimately the cause of his frustrated despair, that he is finally rewarded by entrance into Heaven.
Considered in this philosophical context, Faust's many adventures all communicate the message that to find happiness man must learn to conquer the lower elements of his nature and live constructively within the framework imposed on him. The concluding scenes of the drama and God's statements in the "Prologue" illustrate that good may arise out of evil, but they do not advocate that evil should be sought after as a means for finding the good. The moral doctrine that Goethe puts forward in Faust teaches that the essential feature of all existence and the law that governs the universe is one of untiring, purposeful, and positive effort, and that man can find his place in life only through striving to participate in this vast cosmic movement, although of necessity in terms appropriate to his human capabilities.
Faust's life has its tragic aspects, for his career is marked by a long series of crimes and frustrated illusions and he dies without ever having found complete personal satisfaction, but one recent critic has called Goethe's work "a poem of supreme optimism." This is because the story has a positive and confident conclusion which holds out the inspiring hope that men can find personal gratification in fruitful activity and acceptance of the laws that govern the universe. Faust's long, hard path to Salvation is not intended as an example for others to follow. His experience reveals the pitfalls and false turns that are dangers along the road and is meant to encourage readers in finding their own way to harmony with the cosmic order. The hymn of the Mystical Chorus in the final scene of the drama crystallizes this theme that human fulfillment is the result of communion with the spirit of creativity and action that permeates all life when it says, "Eternal Womanhood/Leads us on high."