Introduction

In the mid-sixties, the philosopher G.H. von Wright proposed to analyse change in terms of a transition operator T (‘and next’) from a certain state described by the proposition ¬φ to a certain state described by the proposition φ. Independently, the linguist J. Gruber proposed to analyse change in terms of a ‘moving’ entity, the Theme, which ‘goes’ from a Source- to a Goal-position.

In both approaches, change is analysed in terms of an initial state and an end state which are related to points of time with respect to which these states are said to hold. However, there is a fundamental difference between the two. On the Von Wright approach, the interval being defined in terms of the initial state and the end state leaves the stretch between them as a sort of no man's land. No information is given by T, so a natural question is: what happened between the two states? All sorts of detailed questions arise, such as: at what point does the transition take place if there is such a point? What does the interval structure look like? What about subintervals? Is there a smallest interval?, etc. (Kamp 1979, 1980; Van Benthem 1983a). This approach put the concept of homogeneity at the centre of attention in the seventies and early eighties.