文档介绍：Bit from It
Julian Barbour
Abstract
With his aphorism ‘it from bit’, Wheeler argued that anything phys-
ical, any it, ultimately derives its very existence entirely from discrete
detector-elicited information-theoretic answers to yes or no quantum bi-
nary choices: bits. In this spirit, many theorists now give ontological
primacy to information. To test the idea, I identify three distinct kinds of
information and find that things, not information, are primary. Examina-
tion of what Wheeler meant by ‘it’ and ‘bit’ then leads me to invert his
aphorism: ‘bit’ derives from ‘it’. I argue that this weakens but not nec-
essarily destroys the argument that nature is fundamentally digital and
continuity an illusion. There may also be implications for the interpre-
tation of quantum mechanics and the nature of time, causality and the
world.
Contents
1 Introduction 1
2 ments 2
3 Kinds of Information 3
4 The Status of Information 6
5 Wheeler’s It and Bit 7
6 Holism and Reductionism 8
7 Appendix A. Maximal Variety 10
8 Appendix B. Best Matching 11
1 Introduction
Quantum information theory has suggested to numerous researchers that the
ground of being – ultimate reality – is information. John Wheeler [1] is the
prophet of this movement. Vlatko Vedral [2] argues that “information is phys-
ical”, and Paul Davies [3] suggests that information is ‘real’ and “occupies the
ontological basement”. Both argue that information is more basic than quan-
tum fields or energy. Moreover, in line with Wheeler’s ‘it from bit’, they take
information, and with it reality, to be digital and to rest ultimately on the
answers to yes/no questions. Continuity is an illusion.
1
To see if such proposals are likely to be correct, we need a definition of
information. What is it? This is the first issue that I address. I distinguish
three kinds of information: as defined by Shannon, as used in normal language,
and as intrinsic semantic information. On this basi