As for Gödel’s incompleteness theorem, it does not in any practical sense rule out a complete theory of physical law. You could perfectly well discover a series of rules which determine the result of every experiment. You could imagine a set of calculation rules such that, if you put to them the question “What will the world look like at date and location so-and-so?”, and began chugging away, they would spit out the answer. What more could you want?
I could imagine a physical universe which followed the rules of Mario physics quite precisely. I could sit down, write up those rules as code, and even simulate that universe. Indeed, it’s already been done, to my great childhood joy. Would anyone deny that there is a small set of formal rules which describes that universe’s physical laws completely? Yet that particular universe is just as subject to Gödel’s incompleteness theorem as anyone else. The Gödelian incompleteness just isn’t a relevant kind of incompleteness; it’s not the sort of thing we would ordinarily consider a failure to completely enumerate physical law.
Here is the only problem Gödel’s incompleteness theorem presents:
Suppose John sits down with some formal physical theory and gets to drawing out all the predictions it produces, with a particular devious plan in mind. He commits himself to ringing a bell whenever, and only whenever, he finds the theory producing the conclusion “John will never ring that bell”.
Then, if the theory ever says “John will never ring that bell”, John will follow it up by immediately disproving the theory. Accordingly, to the extent that the theory is sound, the theory will never make that particular prediction, and thus John will never ring that bell, and thus that the theory’s failure to produce the conclusion “John will never ring that bell” will be failure to draw a true conclusion.
Fine. That is all as it is. But so what? Would we admonish a physical theory as incomplete if it only told us, in painstaking detail, how to calculate whether John would or would not ring the bell by any particular time, without specifically addressing the matter of whether John ever rings the bell? This is weak criticism; what role do statements like “X will never happen” play above and beyond the combined effect of statements like “X will not happen by the year 2000”, “X will not happen by the year 3000”, “X will not happen by the year 4000”, etc.?
The question “Does John ever ring the bell?” plays no role in physics, beyond that played by sharper questions of a sort Gödel puts no proscription on our ability to handle. If someone were to make the mere prediction “John will at some point, eventually, ring that bell”, there’s no way to directly falsify it, since they can always hold “Sure, not yet, but just wait…”. We might well consider such propositions scientifically meaningless. (I would even go so far as to not consider them to have some status as either true or false; I don’t see the value in pretending every such thing automatically has some externally assigned and potentially inaccessible truth status). At any rate, they needn’t be the sort of thing we mean when seeking the complete laws of physics.