Starting from Weber's key distinction between value and instrumental rationality, the concept of value and conviction rationality was defined to make it more precise and serviceable for research, and then some of the factors affecting the ebb and flow of values and convictions were analysed. The dynamics of value systems depend perhaps more than anything else, however, on the relation of those systems to instrumental technique. The interactions on the interface between Weber's two main types of rationality are important in that and in a series of other ways: Weber's distinction between these two types should not be treated as a simple dichotomy: they are an invitation to causal analysis.

Accordingly we must turn to the interface between value and instrumental rationality. The aim is to get a purchase on the infinite variety of historical cases by articulating some causal schemas that help us make sense of the complexity. The following ideal-types of the relation between the two rationalities may usefully be distinguished.

1. (a) Instrumental techniques reproduce values, both extrinsically by making them widely known, and intrinsically by enabling people to internalise them as concrete and vivid.

2. (b) There is an instrumental rationality of spirituality just as much as of the phenomena grouped under the heading of ‘modernity’.

3. (c) Since values mould instrumental rationality, the degree to which instrumental rationality in different cultures coincides depends on the degree of overlap between their value rationalities. To expand this schema: sometimes two or more sets of instrumental rationalities from different cultures seem remarkably alike, and sometimes so dissimilar that it is hard to remember that they are the same kind of rationality: so is instrumental rationality homogeneous or heterogeneous? The key is the causal dependence of instrumental technique on values. […]