Causes.--Three aspects of perception.--Biology and the problem of levels of reality.--Reducibility.--Aristotle and modern biology.--Is genus to species as matter to form?--Two evolutionary theories.--Statistics and selection.--Biology and teleology.--Bohm's metaphysics and biology.--Darwin and philosophy.-- --Explanation and evolution.--On the nature of natural necessity.--On some distinctions between men and brutes.--The characters of living things. I: the biological philosophy of Adolf Portmann.--The characters of living things. II: The phenomenology of Erwin Straus.--The characters of living things. III: Helmuth Plessner's theory of organic models [sic].--People and other animals.