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.