 Currently, the most active subjects of investigation in the domain of foundations and philosophy of computation appear to be the following. First, energy has been invested in developing theories of algorithmic computation on structures other than the natural numbers. In particular, efforts have been made to obtain analogues of Church’s Thesis for algorithmic computation on various structures. In this context, substantial progress has been made in recent decades in developing a theory of effective computation on the real numbers (Pour-El 1999). Second, attempts have been made to explicate notions of computability other than algorithmic computability by humans. One area of particular interest here is the area of quantum computation (Deutsch et al. 2000).