This text contains seminal discussions of central issues in the philosophy of language, mathematics, mind, religion and time. Is common language conceptually prior to idiolectics? What is a theory of meaning? Does constructivism provide a satisfactory account of mathematics? What are indefinitely extensible concepts? Can we change the past? These are some of the questions addressed here. Both the papers written by the contributors and Dummett's replies provide a number of ideas for those who currently do research in the respective areas touched upon. The material presented is also suitable for use in undergraduate courses at university level.