“I hope they’re wrong, but I can’t prove it. And I bet my life work on their being wrong.”
-Andrew Strominger, Harvard University, on skeptics who say that there’s nothing to string theory, Deseret Morning News (Salt Lake City), June 41, 2004.

It seems to me that your voice is being heard. But AS is perhaps referring to Glashow and Veltman.

However, I think that the string community has been a little over critical of string field theory. Many theorists would even like to forget its existence, frequently saying that string theory has “no nonperturbative definition.”

As far as we know, Witten’s cubic open bosonic string field theory gives a full nonperturbative definition of open+closed bosonic string theory. This is not to say that every concievable nonperturbative result in string theory has been reproduced in string field theory. It just means that we have no definitive argument that such nonperturbative information is not there, in principle.

String field theory is a very complicated formalism and is far from unique. There are an infinite number of string field theories, each corresponding to a choice of conformal background and a particular decomposition of the moduli space of Riemann surfaces. There are open string field theories, closed string field theories, open+closed string field theories, superstring field theories… Presumably, each of these could provide a nonperturbative definition of string theory, but certain features which might be obvious in one string field theory (such as the perturbative spectrum around its conformal background) may be quite nontrivial in another (one would first have to construct a classical solution describing the background, and then study fluctuations about this solution). All of these formulations are presumably related by a complicated field redefinition, but our current understanding is primative.

Faced with this situation, most string theorists hope that a more elegant, background independent formulation of string theory will at some point present itself. Personally, I have been inclined to take string field theory seriously, hoping that graudually a deeper understanding of its complicated but presumably profound struncture will emmerge.