This anthology of original essays has been nearly .two and one-half years in the making, and reflects the generous effort of many persons. To begin with, we thank the contributors to the volume, who not only cooperated with regards to their own works, but who also provided valuable advice concerning the over-all volume. One of the contributors was outstanding in his assistance and warrants special mention: we thank Professor Michel Meyer, for his encouragement, counsel, and dedication to see this project to comple tion. We would also like to thank Professor Jaakko Hintikka for his...