Containing the proceedings of the symposium organized to celebrate the 75th anniversary of the founding of the British Ecological Society, this book aims to try and assess the contribution which ecology has made to our understanding of the natural world during the 100 years or so of the discipline's formal existence. The opinions of the whole membership of the society were sought through a postal questionnaire, the results of which are summarized, and to some extent related to the background of the member who replied. The major part of the book consists of 10 essays on the principles identified by the members.