Speculation; a doctrine or scheme of things, which terminates in speculation or contemplation, without a view to practice. It is here taken in an unfavorable sense, as implying something visionary.

An exposition of the general principles of any science; as the theory of music.

The science distinguished from the art; as the theory and practice of medicine.

The philosophical explanation of phenomena, either physical or moral; as Lavoisier’s theory of combustion; Smith’s theory of moral sentiments. Theory is distinguished from hypothesis thus; a theory is founded on inferences drawn from principles which have been established on independent evidence; a hypothesis is a proposition assumed to account for certain phenomena, and has no other evidence of its truth, than that it affords a satisfactory explanation of those phenomena.