Generalizing is an effort to identify connections among traits. The term "connection," though, is pretty vague. What sort of relationship are we talking about? In most cases, we are referring to causality.

The term "causality" covers a very broad range. Different types of causality can be found in different regions of nature and human life, and the various branches of science have developed specialized techniques for studying causality in their own areas. However, we are going to look at a general-purpose technique that will help us identify and analyze causal relationships of any type.

The basis of this technique is a distinction between necessary and sufficient conditions.

A is a necessary condition for B when B cannot exist or occur without A. A is a sufficient condition for B when A is enough to guarantee that B exists or occurs.