"The brightest object known was the sun. Therefore, the stars were assumed to be like the sun, and distances could be estimated from their apparent faintness. In this way, the conception of a stellar system, isolated in space, was formulated as early as 1750. The author was Thomas Wright... But Wright's speculations went beyond the Milky Way. A single stellar system, isolated in the universe, did not satisfy his philosophical mind. He imagined other, similar systems and, as visible evidence of their existence, referred to the mysterious clouds called "nebulæ." Five years later, Immanuel Kant developed Wright's conception in a form that endured, essentially unchanged, for the following century and a half. Some of Kant's remarks concerning the theory furnish an excellent example or reasonable speculation based on the principle of uniformity. ...The theory, which came to be known as the theory of island universes, found a permanent place in the body of philosophical speculation. ...Toward the end of the nineteenth century... the accumulation of observational data brought into prominence the problem of the status of the nebulæ and, with it, the theory of the island universes as a possible solution."