From another conversation...

"As I would put it, there is no essence to the self. At any point one has a certain amount of raw material as given - gender, height, strength, intelligence, language, ethnicity etc. - but this does not exist in abstraction from a contingent historic set of circumstances in which one finds oneself. Whether one 'really' is who and what one says one is (or thinks one is - these doubtless may not be the same thing) is perhaps therefore a question which has no final or unconditional answer.

That said, there are some tolerably reliable indicators. Perhaps the most important of these is whether one can persuade others to accept one's self-description of oneself as a dancer or indeed anything else. And an important issue here will be the question of performance; can one produce a performance of sufficient quality to win approval? Never, of course, unanimous approval, but at least that of a significant minority. Even that is not an absolute test - FN could not get himself accepted in his own lifetime as a philosopher, and Van Gogh only ever sold one painting. But they are extreme examples of visionary genius; for most of us the standards are more clear-cut, and the answer we receive will go a long way towards determining whether one becomes who and what one thinks one is

That is not to deny the importance of a settled disposition on one's own part. If one is perpetually wavering over whether one is or is not a dancer, assuming this self-doubt is not itself an expression of tortured genius, then all other things being equal, it is probably less likely that one 'really is' a dancer. One must play the role consistently. More importantly, one must, in the end, play some role, or more accurately, roles, in one's capacity as a member of a family, a friend, a lover, a worker of some kind, and so on. Failure to be able to play any of these roles effectively, at least most of the time, is ultimately one definition of madness. What constitutes effectiveness is of course itself a moving target as society changes; but the structure of the problem remains the same.

So, I agree - we are all indeed theatre people. It is in the nature of human action and the conditions of selfhood that it must be so. Personality, or better, personation, is inescapably a form of role-playing, and the only relevant questions are what one can bring to the part and how much of it one is capable of inventing for onself. I feel FN was right, in the end, that there are only masks. On your more specific analysis of the illusion on which theatre relies, the presentation of the whole within the part, I have no real comment to make; it seems plausible enough to me, and it even seems that it could be generalised to include all aesthetic forms if one so desired. But I would urge you, once again, to read Ch. XVI of Leviathan, 'Of Persons, Authors, and Things Personated'; Hobbes is marvellously profound on this theme."