What are the basic similarities and differences between classicism and neoclassicism?

Claissicalism represents aesthetic attitudes and principles based on the cultural contributions of ancient Greece and Rome. Classicalism is strongly concerned with society, specifically with a reasoned, civilized, modern society that draws definite distinctions between good and bad. This idea of strict ordering is dependant upon notions of individual objectivity and formal correctness. The details of works were often rather convoluted, much to the self-aggrandizement of the artist.

Neoclassicalism was a movement in the arts which was largely concerned with the "art of the ideal." Details of works were often forcibly constrained to simplistic renderings, and largely geometric composition came into favor. Many neoclassical artists sought inspiration from Greek artists, specifically their portrayal of emotional content, and a concept of naturalism was tightly woven throughout many of their works.