Final answer:
The last four lines of the poem express both the historical context and spiritual themes through reflection of historical events and symbolism.
Step-by-step explanation:
The last four lines of the poem express both the historical context and spiritual themes. They reflect historical events by referencing the political situation in England in 1819, criticizing the government and its corrupt institutions. The poem's spiritual themes are conveyed through the use of symbolism, such as the metaphorical descriptions of the Church, the Parliament, and England. These symbols represent the moral and spiritual decay of society.