The essays in this volume represent an approach to human knowledge that has had a profound influence on many recent thinkers. Popper breaks with a traditional commonsense theory of knowledge that can be traced back to Aristotle. A realist and fallibilist, he argues closely and in simple language that scientific knowledge, once stated in human language, is no longer part of ourselves but a separate entity that grows through critical selection.

Thomas S. Kuhn's classic book is now available with a new index.

Normative theories of obligation, moral and nonmoral value, and meta-ethical issues and theories are considered.