Biology and Physiology. Aristotle applied his ideas of dunamis and immanent teleology most successfully in his works on biology and physiology. These subjects account for the largest share of his extant writings, in fact, and include such important texts as History of Animals, Parts of Animals, Movement of Animals, Generation of Animals, and the group of essays known as the Short Natural Histories or Parua Naturalia. These volumes, all of which were written sometime around 335 B.C.E., exhibit Aristotle's best balance between theory and observation.

Specimens. His research on plants and animals is indeed remarkable for its depth of detail and empirical rigor. These qualities were generally lacking among the earlier Greek scientists, who tended to devote themselves more to theoretical speculation than to observation and experiment. Relying on specimens gathered widely throughout the known world, however, Aristotle himself distinguished...