In certain fields (like Humanities) you can´t possibly catch all the variables. The best thing to do is admit it from the first in your articles. The admission helps future researchers to look for new variables.
Go and have a beer !!!! sounds like you've done enough reading. That is life, there is always missing information. Even the most astute of professors, sometimes miss the obvious - it happens.
In certain fields (like Humanities) you can´t possibly catch all the variables. The best thing to do is admit it from the first in your articles. The admission helps future researchers to look for new variables.
Well, i will not miss the beer and in between i will add "modeling", math and computer simulations tto test the "model" and see what's going on with the current variables... if the model does not fit the facts, then you revise your model... Salud Yoli, cheers!