The question here is what is signified by the lexical token 'theory' in String Theory.

It's something of a rhetorical question because it is, I think, used in a special sense by physicists; for example we have also Chern-Simon Theories or Topological Quantum Field Theories - and these are far from actual physical theories in the sense that a scientifically orientated layman ie without a specialist knowledge of mathematical physics might think of them; this is sometimes acknowledged by the term toy theory ie not a physically appropriate one; and should be compared with, for example, well-established terms such as Newtons Theory of Gravity, or Einsteins Theory of General Relativity.

Here, the theories are buttressed by a complex not only of theoretical standing, but also empirical - ie the falsification criteria of Popper.

But then, it's easy to get confused between how the word theory is used; this suggests that there ought to be a kind of typology of the word theory signifying just how it is used.

One attempt in this direction appears to be the qualifier 'effective'; which suggests that a theory says nothing directly about the ontological status of the notions under consideration, but only that its modelling of physical phenomena is 'effective'.

Has there been any serious work done on distinguishing or characterising how this word is being used by the community in question?

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    I haven't gotten quite that far in my physics education, but to my understanding string theory doesn't even make testable predictions - the work that would go into testing it would require a collider larger than our galaxy, as I understand it? Which, by the strict criterion of "makes testable predictions", disqualifies strings as even a hypothesis, more a postulate. – commando Nov 20 '15 at 17:00
  • One could argue that it is a theory and not merely a hypothesis because it postulates a whole group of laws, not just one. We speak of Netwon's law of inertia, not Newton's theory of inertia. I do tend to agree with commando though, that the lack of testable statements disqualifies it as a theory. – Alexander S King Nov 20 '15 at 17:11
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    It is Theory in the sense of Group Theory, Number Theory, or Theory of Complex Variables, not in the sense of the Theory of Evolution. It is sheer mathematics, and enumerates the variations on possible models that accept a given structure. You can tell the difference in usage because it needs an article, and doesn't get one. – user9166 Nov 20 '15 at 21:09
  • @jobermark: that it doesn't get a definite article is an interesting observation; strange to think that it is this that designates it as a theory to watch. – Mozibur Ullah Nov 20 '15 at 23:09
  • @MoziburUllah "to watch?" I don't get it. There are two senses of 'theory' in English, one is a complex of theorems (Group Theory) or conventions (Music Theory), the other is a thesis with support (the Theory of Evolution). – user9166 Nov 20 '15 at 23:31

Given String Theory's distant relationship to empirical physics, perhaps they are using "Theory" in the mathematical sense, which is just a set of sentences in a formal language. Barring any testable hypotheses, it could be thought of as just a set of axioms which are consistent with observations so far.

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  • This seems likely to me. +1 – Matt Samuel Nov 21 '15 at 8:37

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