The Theory of Natural Philosophy was written in Vienna and is Roger Boscovich’s magnum opus. There are two editions. The first edition, the Vienna edition, was finished while Boscovich was living in Vienna, Austria in the years 1756-1760. In 1758, when Boscovich was age 47, the First, or Vienna, edition appeared. Later in 1763, Boscovich published a second edition in Venice. Significantly the second edition has a completely different title, which reflects a different idea which Boscovich had regarding his finalized system of natural philosophy.