In that case, to answer your original question...
ialdabaoth wrote:
What would be missing from a 'theory of mind' constructed out of our modern understanding of sociology, psychology, and semiotics?
... the answer would be "personal experience".
ialdabaoth wrote:
How would one go about filling in those gaps?
By following the Scientific Method.
1) Develop a new hypothesis. A hypothesis is merely an idea that is usually based on passive observations of natural events. An idea does not have to be supported, but if it does not, then it remains only an idea.
2) Search for related data, which may be found in the results of previous research, whether or not the results of the previous research actually support the previous research.
3) If existing data does not support the hypothesis, then return to step 1.
4) Create a new supporting theory. A theory attempts to explain the hypothesis in a cause-and-effect manner. Never propose a theory that is not supported by available evidence.
5) Perform experiments to test the theory. Experiments must be appropriate to the proposed theory, and must be both repeatable and verifiable.
6) If the experimental results do not support the theory, then return to step 4.
7) Record findings and submit to peer-review process. A peer group is composed of professional researchers in the field of study that the theory addresses. The peer group will first examine the initial data for factual errors, then the theory for errors of reasoning, and then perform the same experiments under the same conditions to validate or invalidate the theory.
8) If the peer-review process produces conflicting evidence, then return to step 4.
9) At this point, the theory becomes a scientific principle.
10) Publish the results.