When we study the evolution of Michelangelo's ideal of form, we find at the beginning of his life a very short period in which he followed the traditions of Donatello and imitated Greek work. The seated Madonna in bas-relief and the Giovannino belong to this first stage. So does the bas-relief of the Centaurs. It soon becomes evident, however, that Michelangelo was not destined to remain a continuator of Donatello's manner or a disciple of the classics. The next period, which includes the Madonna della Febbre, the Bruges Madonna, the Bacchus, the Cupid, and the David, is marked by an intense search after the truth of Nature. Both Madonnas might be criticised for unreality, owing to the enormous development of the thorax and something artificial in the type of face. But all the male figures seem to have been studied from the model. There is an individuality about the character of each, a naturalism, an aiming after realistic expression, which separate this group from previous and subsequent works by Buonarroti. Traces of Donatello's influence survive in the treatment of the long large hands of David, the cast of features selected for that statue, and the working of the feet. Indeed it may be said that Donatello continued through life to affect the genius of Michelangelo by a kind of sympathy, although the elder master's naïveté was soon discarded by the younger.
The second period culminated in the Cartoon for the Battle of Pisa. This design appears to have fixed the style now known to us as Michelangelesque, and the loss of it is therefore irreparable. It exercised the consummate science which he had acquired, his complete mastery over the male nude. It defined his firm resolve to treat linear design from the point of view of sculpture rather than of painting proper. It settled his determination to work exclusively through and by the human figure, rejecting all subordinate elements of decoration. Had we possessed this epoch-making masterpiece, we should probably have known Michelangelo's genius in its flower-period of early ripeness, when anatomical learning was still combined with a sustained dependence upon Nature. The transition from the second to the third stage in this development of form-ideal remains imperfectly explained, because the bathers in the Arno were necessary to account for the difference between the realistic David and the methodically studied genii of the Sistine.