with fewer principles of motion than had originally been employed, the same effects may be more easily produced. The first philosophical systems, in the same manner, are always the most complex, and a particular connecting chain, or principle, is generally thought necessary to unite every two seemingly disjointed appearances; but it often happens that one great connecting principle is afterward found to be sufficient to bind together all the discordant phenomena that occur in a whole species of things.—Adam Smithy Essay on the Principles which Lead and Direct Philosophical Inquiries, as Illustrated by the History of Astronomy.