 Gandy (1980) was one of the first to discuss a version of Modest Physical CTT, arguing that mechanisms with discrete components and reasonable physical limitations (a lower bound on the size of components, and an upper bound on the speed of their kinematics) can only physically compute Turing-computable functions. However, Modest Physical CTT need not be limited in these ways. In addition to physical processes that follow effective procedures, Modest Physical CTT may cover continuous dynamical processes (as in certain kinds of neural networks), processes that span large portions of spacetime, and quantum processes (as in quantum computing). But physical computation does not include all physical processes.