Abstract:Computational implementations are special relations between what is computed and what computes it. Though the word "isomorphism" appears in philosophical discussions about the nature of implementations, it is used only metaphorically. Here we discuss computation in the precise language of abstract algebra. The capability of emulating computers is the defining property of computers. Such a chain of emulation is ultimately grounded in an algebraic object, a full transformation semigroup. Mathematically, emulation is defined by structure preserving maps (morphisms) between semigroups. These are systematic, very special relationships, crucial for defining implementation. In contrast, interpretations are general functions with no morphic properties. They can be used to derive semantic content from computations. Hierarchical structure imposed on a computational structure plays a similar semantic role. Beyond bringing precision into the investigation, the algebraic approach also sheds light on the interplay between time and computation.Keywords: computation; abstract algebra; semigroup theory; finite automata; homomorphism; hierarchical structure; finiteness and universality The steam engine replaced muscle power. It did not just make life easier, but a whole bunch of impossible things became possible. Curiously, it was invented before we understood how it worked. Afterward, trying to make it more efficient led to thermodynamics and indirectly to a deeper understanding of the physical world. Similarly, computers replace brain power, but we still do not have a full comprehension of computation. Trying to make computation more efficient and to find its limits is taking us to a deeper understanding of not just computer science, but of other branches of science (e.g., biology, physics, and mathematics). Just as physics advanced by focusing on the very small (particles) and on the very large (universe), studying computers should also focus on basic building blocks (finite state computations) and on large-scale abstract structures (hierarchical (de)compositions).Another parallel with physics is that the underlying theory of computation is mathematical. Algebraic automata theory is a well-established part of theoretical computer science [1][2][3][4][5]. From a strictly technical point of view, it is not necessary to discuss computation at the algebraic level. Several excellent textbooks on the theory of computation do not even mention semigroups [6][7][8]. However, we argue here that for doing a more philosophical investigation of computation, semigroup theory provides the right framework.The following theses summarize the key points of the algebraic view of computation:1. Computation has an abstract algebraic structure. Semigroups (sets with associative binary operation) are natural generalizations of models of computation (Turing machines, λ-calculus, finite state automata, etc.).Philosophies 2018, 3, 00; doi:10.3390/philosophies3020015 www.mdpi.com/journal/philosophies Philosophies 2018, 3, 00 2 of 14 2. Algebraic...