Introduction

Explanations are a vital part of daily life. We often give and receive them, explaining the results of elections, the changes in the weather, or our own behaviour to one another. In the scholarly enterprise they are even more important. While the researcher who discovers important facts will be respected, the scientist who explains them may be in line for a Nobel prize. Those features of the world that we cannot explain are a major focus of research, even if we know a great deal about them.