In Chapter 5 we considered the quality of links between classes in a network and suggested that this varies considerably. So far, however, we have not considered another way in which the association between classes may vary. This is the strength of any given link in the network. In the first part of this chapter we consider the problem of induction and attempts to measure ‘rational degrees of belief’ in terms of the so-called theory of personalist probability. In the second part we informally introduce questions of probability and utility.