As such they are very well-known to all those who study and do research in certain areas of mathematics. The formidable background needed to understand their work, however, prevents many others from appreciating its significance. The articles collected here are written to help create such an appreciation. Not all those who were invited to write for this volume agreed to do so, not all who agreed kept their promise, and not all articles we finally received are included here. Therefore, this collection is far less complete than what we had originally planned. We hope there will be a sequel that would redress this. Ten years later the travails were forgotten, and we began work on the promised sequel. The present collection is the outcome. This too is far less complete than we planned, and for the same reasons. We do hope that it will be of as much interest as the first collection, and that this too will have a sequel. We thank our authors for the huge amount of time and effort they spent in writing their pieces, and for patiently waiting while we got the collection together. We thank several colleagues who read the drafts of these articles and made suggestions for changes.