So which faculty will tell you? The one that looks at both itself and everything else. What faculty is that? Your rational mind. It's the only faculty you have that can examine itself — what it is, what power it has, what value this gift holds — and examine all other faculties too. What else tells us that golden things are beautiful? The gold doesn't say so itself. Clearly, it's the faculty that can judge appearances. What else judges music, grammar, and other abilities? What else proves their uses and shows when to use them? Nothing else.
What faculty then will tell you? That which contemplates both itself and all other things. And what is this faculty? The rational faculty; for this is the only faculty that we have received which examines itself, what it is, and what power it has, and what is the value of this gift, and examines all other faculties: for what else is there which tells us that golden things are beautiful, for they do not say so themselves? Evidently it is the faculty which is capable of judging of appearances. What else judges of music, grammar, and the other faculties, proves their uses, and points out the occasions for using them? Nothing else.