 The relationship between these four seems rather straightforward. (O4) will have to say how the other three are supposed to be understood. In particular, it will have to tell us if the question to be answered in (O2) indeed is the question what there is, which was taken above to be only a first approximation for how to state what ontology is supposed to do. Maybe it is supposed to answer the question what is real instead, or what is fundamental, some other question. Whatever one says here will also affect how one should understand (O1). We will at first work with what is the most common way to understand (O2) and (O1), and discuss alternatives in turn. If (O1) has the result that the beliefs we share commit us to a certain kind of entity then this requires us either to accept an answer to a question about what there is in the sense of (O2) or to revise our beliefs. If we accept that there is such an entity in (O2) then this invites questions in (O3) about its nature and the general relations it has to other things we also accept. On the other hand, investigations in (O3) into the nature of entities that we are not committed to and that we have no reason to believe exist would seem like a rather speculative project, though, of course, it could still be fun and interesting.