This volume presents the outcome of a workshop, held in Amsterdam in 1985, on the nature, even possibility, of explanation in Historical Linguistics: why changes take place and others do not, and why they occur at a particular time and place. The workshop, and this volume, aim to explore questions such as i) are the factors which explain the actuation of a change different from those that explain its implementation?; ii) is it possible to give a typology of changes?; iii) should linguistic explanation hope to meet the same requirements as explanation in the pure sciences?; iv) are all linguistic changes necessarily the product of variation?; v) should there be a formal theory of change apart from a general thoery of grammar?