Journal of Philosophical Logic

, Volume 28, Issue 2, pp 141–164

Mirror notation: symbol manipulation without inscription manipulation

  • Roy A. Sorensen

DOI: 10.1023/A:1004307405785

Cite this article as:
Sorensen, R.A. Journal of Philosophical Logic (1999) 28: 141. doi:10.1023/A:1004307405785


Stereotypically, computation involves intrinsic changes to the medium of representation: writing new symbols, erasing old symbols, turning gears, flipping switches, sliding abacus beads. Perspectival computation leaves the original inscriptions untouched. The problem solver obtains the output by merely alters his orientation toward the input. There is no rewriting or copying of the input inscriptions; the output inscriptions are numerically identical to the input inscriptions. This suggests a loophole through some of the computational limits apparently imposed by physics. There can be symbol manipulation without inscription manipulation because symbols are complex objects that have manipulatable elements besides their inscriptions. Since a written symbol is an ordered pair of consisting of a shape and the reader's orientation to that inscription, the symbol can be changed by changing the orientation rather than inscription. Although there are the usual physical limits associated with reading the answer, the computation is itself instantaneous. This is true even when the sub-calculations are algorithmically complex, exponentially increasing or even infinite.

algorithmic complexity computation Cambridge event duals mirror NP-completeness symbol manipulation Turing machine 

Copyright information

© Kluwer Academic Publishers 1999

Authors and Affiliations

  • Roy A. Sorensen
    • 1
  1. 1.Department of PhilosophyNew York UniversityU.S.A.

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