The reader who has followed the development of this book from the beginning will recognise a progressive increase in the degree of speculation, chapter upon chapter; after describing the basic experimental phenomena, we began with a treatment of relaxation in simple molecules, which is virtually irrefutable, and ended up with an attempt to treat in a semiquantitative manner such concepts as those of randomisation and of activation bottlenecks, about which we still know really very little. For the sake of brevity, I have tried to keep the speculation to the minimum required to form a consistent foundation for the treatment of unimolecular reaction manifestations, wherever they may occur. My discussion has concentrated almost solely on the shape of the fall-off curve for a few thermal unimolecular reactions: this, despite the fact that I enumerated other interesting properties of simple thermal reactions in Chapter 1, and omitted entirely to mention the wide range of other experimental properties usually encompassed within the general topic of unimolecular reaction theory [72.R; 73.F]. In conclusion, therefore, I would now like to hold a brief inspection of each of those topics raised in Chapter 1, together with a few others so far not mentioned, to see how successful the present theory appears to be.