When we talk, we are always talking about something, and when we reason, we are always reasoning about something. But it is possible to take ourselves to be talking or reasoning about something when in fact we are talking or reasoning about something else. In fact, I think this happens all the time in philosophy.

In order to reason about something, it is necessary to take the object of our reasoning as being something or other, e.g. as being an X. We can only reason about a thing by giving it some content in our minds by taking it as being of some sort or other. But we can also reason about this…