ABSTRACT
This chapter describes the network model for scientific theorizing in qualitative terms. However, a branch of mathematics which deals with networks at a quantitative level called graph theory. In a graph a walk is an alternating sequence of nodes and edges which are connected together. If all the edges are distinct then the walk is referred to as a trail. If all the nodes and edges are distinct then it is referred to as a path. In a directed graph a path follows the directions of the arrows. Condensation is a neat example of the mathematical language of graph theory mirroring the language of scientific theory. A common way to represent graphs is to use matrix algebra. For a digraph we can define the adjacency matrix. The rows and columns refer to start and end points of arcs, with the numbers in the matrix referring to the number of arcs joining the corresponding vertices in the digraph.
