## Abstract

The algorithm, a building block of computer science, is defined from an intuitive and pragmatic point of view, through a methodological lens of philosophy rather than that of formal computation. The treatment extracts properties of abstraction, control, structure, finiteness, effective mechanism, and imperativity, and intentional aspects of goal and preconditions. The focus on the algorithm as a robust conceptual object obviates issues of correctness and minimality. Neither the articulation of an algorithm nor the dynamic process constitute the algorithm itself. Analysis for implications in computer science and philosophy reveals unexpected results, new questions, and new perspectives on current questions, including the relationship between our informally construed algorithms and Turing machines. Exploration in terms of current computational and philosophical thinking invites further developments.

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## Notes

- 1.
I am indebted to Ksenia Tatarchenko, who introduced me to the work of the 1979 symposium

*Algorithms in Modern Mathematics and Computer Science*in her talk at the 2014 conference of the International Association for Computing and Philosophy. - 2.
In my earlier letter to the editor (Hill 2013), I offered a definition that said “expressed in a finite, imperative form.” This has turned out to be misleading; the expression is independent of the algorithm, as is discussed in Section 5.5. The letter also used the term “deterministic” rather than “effective.”

- 3.
Note that although Cleland uses the word “order” a few lines later as a noun to mean “correct sequence,” she seems to be using “order” in this passage to mean “command,” referring to the imperative.

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## Acknowledgments

I wish to thank William J. Rapaport of the University at Buffalo for his cogent suggestions and steady encouragement, and to note that any failing in the ideas or treatment is mine alone. Anonymous reviewers improved this work via many good suggestions, and have my sincere gratitude.

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Hill, R.K. What an Algorithm Is.
*Philos. Technol.* **29, **35–59 (2016). https://doi.org/10.1007/s13347-014-0184-5

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### Keywords

- Algorithm
- Philosophy of computer science
- Church-Turing thesis
- Mathematical ontology