adequate architectonic of laws for constrained, as well as unconstrained, motions." For Leibniz, like Aristotle, this law of nature concerning entelechies was also understood as a metaphysical law, important not only for physics, but also for understanding life and the soul. A soul, or spirit, according to Leibniz, can be understood as a type of entelechy (or living monad) which has distinct perceptions and memory. Influence on modern physics Ideas about potentiality have been related to quantum mechanics, where a wave function in a superposition of potential values (before measurement) has the potential to collapse into one of those values, under the Copenhagen interpretation of quantum mechanics. In particular, the German physicist Werner Heisenberg called this "a quantitative version of the old concept of ‘potentia’ in Aristotelian philosophy". in modern philosophy and biology As discussed above, terms derived from and have become parts of modern scientific vocabulary with a very different meaning from Aristotle's. The original meanings are not used by modern philosophers unless they are commenting on classical or medieval philosophy. In contrast, , in the form of entelechy is a word used much less in technical senses in recent times. As mentioned above, the concept had occupied a central position in the metaphysics of Leibniz, and is closely related to his monad in the sense that each sentient entity contains its own entire universe within it. But Leibniz' use of this concept influenced more than just the development of the vocabulary of modern physics. Leibniz was also one of the main inspirations for the important movement in philosophy known as German Idealism, and within this movement and schools influenced by it entelechy may denote a force propelling one to self-fulfillment. In the biological vitalism of Hans Driesch, living things develop by entelechy, a common purposive and organising field. Leading vitalists like Driesch argued that many of the basic problems of biology cannot be solved by a philosophy in which the organism is simply considered a machine. Vitalism and its concepts like entelechy have since been discarded as without value for scientific practice by the overwhelming majority of professional biologists. However, in philosophy aspects and applications of the concept of entelechy have been explored by scientifically interested philosophers and philosophically inclined scientists alike. One example was the American critic and philosopher Kenneth Burke (1897–1993) whose concept of the "terministic screens" illustrates his thought on the subject. Prof Denis Noble