When I endeavour to examine my own conduct, when I endeavour to pass sentence upon it, and either to approve or condemn it, it is evident that, in all such cases, I divide myself, as it were, into two persons; and that I, the examiner and judge, represent a different character from that other I, the person whose conduct is examined into and judged of. The first is the spectator, whose sentiments with regard to my own conduct I endeavour to enter into, by placing myself in his situation, and by considering how it would appear to me, when seen from that particular point of view. The second is the agent, the person whom I properly call myself, and of whose conduct, under the character of a spectator, I was endeavouring to form some opinion. The first is the judge; the second the person judged of. (Adam Smith, Theory of Moral Sentiments, III.i.6)

Quis custodiet ipsos custodes? (Juvenal, Satire VI, lines 347–348)

According to Adam Smith, each person divides himself into two persons. Person #1 is himself (the ego), while Person #2 is an external judge or spectator. Sometimes, Smith refers to this imaginary alter ego as “the man within the breast” (see here, for example), and at other times, he calls him the “impartial spectator” or “supposed impartial spectator” (again, see here). But regardless whether the impartial spectator and the man within the breast are one in the same or are two separate entities (i.e. the key question that my colleagues Daniel Klein, Nicholas Swanson, and Jeffrey Young recently brought to my attention and that I have been writing about this past week), I will now conclude my series on Adam Smith’s impartial spectator with a totally different question: who spectates the impartial spectator? That is, if each person has an internal man within his breast inside him, and if each person’s moral decisions are reviewed by this man within his breast, and (assuming the impartial spectator and the man within the breast are two distinct entities) if this man within the breast is, in turn, checked by a higher-level impartial spectator, then who checks the impartial spectator?