  So, when I say that my desk still exists after I leave my office, perhaps I just mean that I would perceive it if I were in my office, or, more broadly, that a finite mind would perceive the desk were it in the appropriate circumstances (in my office, with the lights on, with eyes open, etc.). This is to provide a sort of counterfactual analysis of the continued existence of unperceived objects. The truth of the counterfactuals in question is anchored in regularity: because God follows set patterns in the way he causes ideas, I would have a desk idea if I were in the office.