Shelley investigates several different dualities in The Triumph of Life, including light and dark, young and old, as well as passion and restraint. The poem opens with the duality of night and day, which is part of the imagery of light and dark. In the introductory section of the poem, the “Sun sprang forth / Rejoicing in his splendour, and the mask / Of darkness fell from the awakened Earth” (Lines 2-4). The light of the sun replaces the darkness of night. The poem covers the visionary events of a day, with images of the day growing old at the end of the fourth section. Rousseau discusses when “the day / was old” (Lines 537-38). Here, darkness is associated with aging and eventual death. The duality of light and dark is also used to describe the “strange trance” (Line 29) that comes over Shelley. The “shade it spread / Was so transparent that the scene came through / As clear as when a veil of light is drawn / O’er evening hills” (Lines 30-33). Shade usually represents an element of darkness but, here, it is compared to light. This simile is a blending of light and dark.

The investigation of dualities continues within the visions of Shelley and Rousseau.