SOURCE: “A Plurality of Worlds,” in Seeing New Worlds: Henry David Thoreau and Nineteenth-Century Nature Science, University of Wisconsin Press, 1995, pp. 167-211.

In the following excerpt, Walls surveys nineteenth-century theories about the plurality of worlds in the context of several notable non-fiction works of the time.

We might try our lives by a thousand simple tests; as, for instance, that the same sun which ripens my beans illumines at once a system of earths like ours. If I had remembered this it would have prevented some mistakes.

—Henry David Thoreau, Walden

One of the controversies that enlivened scientific discourse of the 1840s and 1850s concerned the possible plurality of worlds. Was earth unique, or was there, as Thoreau fancied in Walden, “a system of earths like ours”? The controversy turned on integrating the findings of the new science of geology with the older science of astronomy, or deep...