tychism (from Greek tyche, ‘chance’), Peirce’s doctrine that there is absolute chance in the universe and its fundamental laws are probabilistic and inexact. Peirce’s tychism is part of his evolutionary cosmology, according to which all regularities of nature are products of growth and development, i.e., results of evolution. The laws of nature develop over time and become increasingly rigid and exact; the apparently deterministic laws of physics are limiting cases of the basic, probabilistic laws. Underlying all other laws is ‘the tendency of all things to take habits’; Peirce calls this the Law of Habit. In his cosmology his tychism is associated with synechism, the doctrine of the continuity of nature. His synechism involves the doctrine of the continuity of mind and matter; Peirce sometimes expressed this view by saying that ‘matter is effete mind.’ R.Hi.