Nir Fresco does a very good job of gathering most, if not all, of the traditional approaches to the question: “What is computation?” Perhaps the most unconventional approach is presented in the last chapter, in which the author wraps up his own ideas, proposing that the question is ultimately related to the cognitive sciences.

I would have personally liked to see more contemporary approaches to the question. While the traditional stance is that the “everything computes” trivialization has failed because it makes no contribution to the debate, in practice, it is the other way around that seems to be prevailing. Indeed, whole new areas under the umbrella of natural and unconventional computing are founded on the very basis of the “everything (can) compute(s)” dogma, from popular examples of slime mold [1] to accounts of the universe as a digital causal network [2] or as a giant quantum computer [3] (there are additional broad [4] and specific examples [5,6] for interested readers).

None of this seems to be covered by Fresco, possibly because he focuses on providing a thorough account of the conventional approach to the question of computation, coming from decades of debate, proposals, and counterproposals around mostly a handful of important assumptions deeply related to computation. Fresco does an excellent job in this regard. Every chapter has been published in top journals devoted to the philosophy of computing, and I only regret the lack of author and topic indexes, which would have facilitated finding further information on specific subjects.