The papers presented at the Chicago Darwin Centennial suggest a fresh approach to the philosophical problem of ends in nature. In order to avoid the implications of “teleology,” assumed to refer only to the process of evolution as directed towards goals, the discussants use “teleonomy” in reference to the biological organism as end-directed (for reproduction). They accept “teleonomy” only as descriptive, and neglect its significance for theory.The present thesis is that each of the three recognized phases of universal evolution: inorganic, organic, and post-organic initiated by the advent of man and his culture, is characterized and made possible by the emergence of a distinctive type of teleonomic organization. While the process of evolutionary change is not itself end-directed to any goal, the end-directed structures which arise are not only “in nature” but are themselves crucial factors in evolution, since it is on them that natural selection operates. By using the concept of teleonomy, it is argued, one can avoid the issue of “mechanism” versus “teleology.”