In “Continuities”, Whitman seems to be challenging what is vs. what we perceive. Whitman suggests that people are often taken from the truth when evaluating the superficial. The phrase “what you see is what you get” comes to mind when considering this poem; Whitman, however disagrees with this as we see in the line “Appearance must not foil, nor shifted sphere confuse thy brain.” Whitman urges his readers not to be confused by appearances or changing physical spheres because “nothing is ever really lost, or can be lost.” He attributes this to identity, force, visible things, objects; he suggests that because these things can never be lost, they just shift in physical sphere. The spirit of these things are always as they were.
Whitman suggests that the natural world moves through these spheres and appearances through a mode of natural continuity. “Time and space are ample”, meaning that there always is and always will be enough time and space for movement and growth within the natural world. The natural world merely follows a continuity of cycle, as Whitman describes various forms of natural continuity referring to the cycle of the seasons, the rising and setting of the sun, etc. Whitman realizes that these physical spheres will change: “The aging body ” and as a result, we will respond with a “dimming eye”. But he encourages us not to be concerned with the changing physical spheres; the body is merely responsive to natural continuity. The body follows the natural cycle of the world, and thus it is natural for us to age. The consequences of age are necessary for this continuity; just as the world around us loses its leaves in the winter, we figuratively lose our leaves.
If Whitman is following this theory of natural continuity, it seems that he attributes a sort of reincarnation to the human spirit. Though we age and our physical spheres change, things will always be as they were because time and Nature are continuous. Just as Nature is reborn in the Spring, so are we.