Even though Shelley's sonnet had its origin in a humorous challenge between Shelley and his friend Horace Smith, "Ozymandias" (1818) is a poetic argument whose thesis is that human pride and monuments to power, indeed, life itself, is transient and essentially meaningless.
The sonnet is set in an "antique land," one of the favorite settings for poets of the Romantic Period (the more exotic, the better). The traveler recounts having seen, in a waste of desert,
Two vast and trunkless legs of stone
Stand in the desert. Near them on the sand,
Half sunk, a shattered visage lies. . . .
We are introduced to Ozymandias (the Greek name for Rameses the Great, one of Egypt's most powerful rulers) not as an intact and impressive image but in barely recognizable pieces scattered over the desert. Shelley subtly frames the subject of his sonnet as both powerful ("vast") and powerless ("shattered"), the symbol of two forces that are in constant tension in human life--on one hand, human pride and the drive for permanence, and, on the other hand, nature's overwhelming power to make human pride a laughable concept.
The subject of these opposing forces, Rameses, was an impressive and successful ruler, and his strength of character is captured by the sculptor:
And wrinkled lip and sneer of cold command
Tell that its sculptor well those passions read
Which yet survive, stamped on these lifeless things,
In order for Shelley to frame his argument that life is transient, and that human pride is a momentary rather than a permanent reality, he must emphasize the commanding presence that once characterized Rameses, whose "wrinkled lip and sneer" depicts a man who wears his power like a comfortable shirt and is not reluctant to use it.
Rameses himself articulates the power and pride with which he views the world he has created:
`My name is Ozymandias, King of Kings:
Look on my works, ye mighty, and despair!'
In other words, for any of you kings who think you are the ultimate in power, just look at these monuments, and you will [unless you are foolish], give up all hope of competing with my greatness. The boast, of course, is immediately rendered both sad and foolish by the following line, which notes that "nothing beside remains," that is, the boast is all that is left intact.
Shelley has artfully created a poetic argument at the core of his own belief system--that all empires are destined to disappear. Despite all the power and pride that humanity can muster, including monuments in stone, time and nature will bring all human endeavors to a "colossal wreck."