Chapter 8 focusses on the nature of the second binary opposition, the one between SYN and POST. In view of the fact that POST can be argued to be modal, the leading idea is that the opposition can be understood in terms of a strict opposition between realis (indicative) and different forms of irrealis (subjunctive, conjunctive, etc). The chapter culminates in reaching S’ at the end of the journey from the tenseless bottom of phrase structure to the tensed top S’ including all the distinctions made on the way between the different factors summarized at the end of Chapter 5. This makes it possible to see binary tense structure as expressing tense, mood and aspect in a systematic compositional way.

How ontologically committal is common sense? Is the common-sense philosopher beholden to a florid ontology in which all manner of objects, substances, and processes exist and are as they appear to be to common sense, or can she remain neutral on questions about the existence and nature of many things because common sense is largely non-committal? This chapter explores and tentatively evaluates three different approaches to answering these questions. The first applies standard accounts of ontological commitment to common-sense claims. This leads to the surprising and counter-intuitive result that common sense has metaphysically heavyweight commitments. The second approach emphasizes the superficiality and locality of common-sense claims. On this approach, however, common sense comes out as almost entirely non-committal. The third approach questions the seriousness of ontological commitment as such. If ontological commitment is cheap, it becomes possible both to accept the commitments of common sense at face value and to avoid the counter-intuitive consequences of heavyweight metaphysical commitments.