In addition, perhaps I'm doing Galileo a disservice here because he did say that
“we cannot understand [Nature] if we do not first learn the language and grasp the symbols in which it is written”.
Yes, Galileo was talking about our understanding of Nature - not just Nature as it is (as it were) “in itself”. Nonetheless, Galileo also said that the “book is written in mathematical language”. So was he also arguing that Nature as it is in itself is mathematical? That is, perhaps Galileo wasn't only saying that mathematics is required to understand Nature.
There is, therefore, an ambivalence here between the following:
To change tack a little.
The physicist John Archibald Wheeler provided the best riposte to Pythagoreanism in physics. We're told that Wheeler used to write many arcane equations on the blackboard and stand back and say to his students:
“Now I'll clap my hands and a universe will spring into existence.”
According to Pythagoreans, however, the equations are the universe.
Then Steven Hawking trumped Wheeler with an even better-known quote. He wrote:
“Even if there is only one possible unified theory, it is just a set of rules and equations. What is it that breathes fire into the equations and makes a universe for them to describe?”
So what, exactly, “breathes fire into the equation [to] make a world”?
To return to string theory.
Kaku himself puts what can be seen as the extreme place which string theory finds itself in. He writes:
Much is made of the fact that many mathematicians and physicists stress the “beauty” and “elegance” of their theories. In terms of string theory, perhaps these aesthetic values may provide string theory's main appeal.
Smolin quotes string theorists talking about the beauty of the theory in the following:
“... 'How can you not see the beauty of the theory? How could a theory do all this and not be true?' say the string theorists.”
Smolin is at his most explicit when he also tells us that “string theorists are passionate about is that the theory is beautiful or 'elegant'”. However, he says that
“[t]his is something of an aesthetic judgment that people may disagree about, so I'm not sure how it should be evaluated”.
“In any case, [aesthetics] has no role in an objective assessment of the accomplishments of the theory.... lots of beautiful theories have turned out to have nothing to do with nature.”
So perhaps that highly-complicated maths is but a means to secure us simplicity and explanation. That is, the work done towards simplicity and explanation is very complex and difficult; though the result – a theory which is both simple and highly explanatory – evidently isn't.