The Beginning of Infinity

~ David Deutsch, 2011

The Theory of Everything

The reason why higher-level subjects can be studied at all is that under special circumstances the stupendously complex behaviour of vast numbers of particles resolves itself into a measure of simplicity and comprehensibility. This is called emergence: high-level simplicity 'emerges' from low-level complexity. High-level phenomena about which there are comprehensible facts that are not simply deducible from lower-level theories are called emergent phenomena. For example, a wall might be string because its builders feared that their enemies might try to force their way thought it . This is high-level explanation of the wall's strength, not deducible from (though not incompatible with) the low-level explanation I gave above. 'Builders', 'enemies', 'fear' and 'trying' are all emergent phenomena. The purpose of high-level sciences is to enable us to understand emergent phenomena, of which the most important are, as we shall see, life, thought and computation

Terminology

Epistemology : The study of the nature of knowledge and the processes that create it.

Instrumentalism : The view that the purpose of a scientific theory is to predict the outcomes of experiments.

Reductive : A reductive explanation is one that works by analysing things into lower-level components.

Reductionism : The view that scientific explanations are inherently reductive.

Holism : The idea that the only legitimate explanations are in terms of higher-level systems; the opposite of reductionism.

Emergence : An emergent phenomenon is one (such as life, thought or computation) about which there are comprehensible facts or explanations that are not simply deducible from lower-level theories, but which may be explicable or predictable by higher-level theories referring directly to that phenomenon.

Summary

Scientific knowledge, like all human knowledge, consists primarily of explanations. Mere facts can be looked up, and predictions are important only for conducting crucial experimental tests to discriminate between competing scientific theories that have already passed the test of being good explanations. As new theories supersede old ones, our knowledge is becoming both broader (as new subjects are created) and deeper (as our fundamental theories explain more, and become more general). Depth is winning. Thus we are not heading away from a state in which one person could understand everything that was understood, but towards it. Our deepest theories are becoming so integrated with one another that they can be understood only jointly, as a single theory of a unified fabric of reality. This Theory of Everzthing has a far wider scope than the 'theory of everything' that elementary particle physicists are seeking, because the fabric ofreality does not consists only of reductionist ingredients such as space, time and subatomic particles, but also, for example, of life, thought and somputation. The four main strands of explanation which may constitute the first Theory of Everything are:

The Criteria for Reality

Explanations are not justified by the means by which they were derived; they are justified by their superior ability, relative to rival explanations, to solve the problems they address. That is why the argument that a theory is indefensible can be so compelling. A predictions, or any assertion, that cannot be defended is not an explanation. The rejection of 'mere' explanations on the grounds that they are not justified by any ultimate explanation inevitably propels one into futile searches for an ultimate source of justification. There is no such source.

We need to develop reasons for accepting or rejecting the existence of entities that may appear in contenting theories; in other words, we need a criterion for reality. We should not, of course, expect to find a final or an infallible criterion. Our judgments of what is or is not real always depend on the various explanations that are available to us, and sometimes change as our explanations improve.

If, according to the simplest explanation, an entity is complex and autonomous, then that entity is real.

Scientific reasoning is reliable, not in the sense that it certifies that any particular theory will survive unchanged, even until tomorrow, but in the sense that we are right to rely on it. For we are right to seek solutions to problems rather than sources of ultimate justification. Observational evidence is indeed evidence, not in the sense that any theory can be deduced, induced or in any other way inferred from int, but in the sense that it can constitute a genuine reason for preferring one theory to another

Summary

Real entities behave in a complex and autonomous way, which can be taken as the criterion for reality: if something 'kicks back', it exists. Scientific reasoning, which uses observation not as a basis for extrapolation but to distinguish between otherwise equally good explanations, can give us genuine knowledge about reality.