by Henk Barendregt (Author)

This book is an extended version of the author's 1971 PhD thesis, containing a facsimile of the original and several extensions: motivation, hindsight and the making of. It is concerned with consistency of equating unsolvable terms and adding the omega-rule as strengthening of the principle of extensionality. The republication is put in context of the transition of lambda-calculus from an academic theory to a major foundation for fruitful aspects of logic, having an impact on mathematics and computer science and technology with a societal impact by securing correctness of complex systems.