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Constructor theory


Constructor theory seeks to express all fundamental scientific theories in terms of a dichotomy between possible and impossible physical transformations–those that can be caused to happen and those that cannot. This is a departure from the prevailing conception of fundamental physics which is to predict what will happen from initial conditions and laws of motion. Several converging motivations for expecting constructor theory to be a fundamental branch of physics are discussed. Some principles of the theory are suggested and its potential for solving various problems and achieving various unifications is explored. These include providing a theory of information underlying classical and quantum information; generalising the theory of computation to include all physical transformations; unifying formal statements of conservation laws with the stronger operational ones (such as the ruling-out of perpetual motion machines); expressing the principles of testability and of the computability of nature (currently deemed methodological and metaphysical respectively) as laws of physics; allowing exact statements of emergent laws (such as the second law of thermodynamics); and expressing certain apparently anthropocentric attributes such as knowledge in physical terms.

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  1. For example, the most formal treatments of the second law, such as Carathéodory’s, simply assume the existence of ‘macro’-states.

  2. In this paper the term ‘information’ means classical information. A more general notion, which includes both quantum information and physically irreversible media, can likewise be defined in purely constructor-theoretic terms. This will be discussed in a future paper.

  3. For a discussion of what makes an explanation ‘good’, see (Deutsch (2011), Chap. 1).

  4. Referring to the Biblical story of the pharaoh who ordered that the Israelite slaves find their own brick-making materials instead of transforming a given supply.


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I am grateful to Simon Benjamin for pointing out some subtleties including the non-existence of a universal classical constructor, to him and Mark Probst for illuminating conversations on the themes of this paper, to Alan Forrester and two anonymous referees for numerous useful suggestions, and especially to Chiara Marletto for incisive criticism of earlier versions of the theory and of earlier drafts of this paper.

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Correspondence to David Deutsch.

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Deutsch, D. Constructor theory. Synthese 190, 4331–4359 (2013).

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  • Constructor theory
  • Von Neumann machines
  • Physics of computation