Let's all try to understand some of the shades of meaning of the word theory, and try to be polite to each other, shall we?
Theory has two broad senses in common use, which I think of as the weak sense and the strong sense. In the weak sense, it's used to mean a belief, conjecture, or speculation. In the strong sense it means a coherent, consistent body of data, ideas, information, and analyses that describe and explain a range of phenomena. Evolution, for instance, is a theory in the strong sense, and people who dismiss it as only a theory are confusing that meaning, sometimes deliberately I think, with the weak sense and committing a common logical error called the fallacy of equivocation.
There are two further divisions in the strong sense: there are scientific theories and non-scientific theories, and the distinction is based on empiricism, which in this context means based on observation and experiment: scientific theories are empirical, non-scientific theories are not. Picture it this way:
Theory
1. Weak Sense
a belief, conjecture, or speculation
2. Strong Sense
a coherent, consistent body of data, ideas, information, and analyses that describe and explain a range of phenomena.
(
a) Non-Scientific(i) Empirical, but not falsifiable, predictive, or testable, like psychoanalysis and, so far, string theory.
(ii) Non-Empirical, also not falsifiable, predictive, or testable, like religious dogma
(b) Scientific: empirical, falsifiable, predictive, and testable
Might be a bit of a stretch to call string theory empirical, there are no observations or experiments that directly suggest it, there are only negatives, like the observed inconsistencies between quantum theory and relativity that indicate some deeper explanation is necessary. The essential point remains, however: string theory is not yet a scientific theory.
