“Contrapposto” is a characteristic Classical figural construction. Antithesis is the basis of Contrapposto and brings most of its traditional literary meanings with it in the Renaissance language. Alberti’s Della Pittura is important source for Summers’ interpretation of Contrapposto in Renaissance art.
Alberti finds contrapposto to be an exaggerated gesture and therefore undesirable for proper art; he states: "There are those who express too animated movements, making the chest and the small of the back visible at once in the same figure, an impossible and inappropriate [non condicente] thing (Della Pittura 96,97)". Alberti's position can be traced back to Quintialian—who saw in excessive affectation of the postures "a fault in every kind of style" (Quintilian VIII. iii. 56) attributable to ingenium (creativity) taking over iudicium (good judgement)—and to Plato, who calls too much bodily torsion, such that its visible from front and back "disorderly and irrational" (Plato, Timeaus 43B).
Taking into consideration these views, one can see what made contrapposto such an interesting subject to consider per se, since its use in Renaissance art not only embodied the rich concept of antithesis, but it also served as introduction to the theme of the usage of ornament in pictorial composition.
Michelangelo, David. 1501-1504. Marble. Galleria dell'Accademia, Florence.