On the idea(l) of logical closure (Q1192341)

The author, an eminent logician, whose voluminous work plays an influental role in the development of contemporary proof theory and foundations of mathematics, discusses different interesting aspects of a fundamental notion of logic --- the notion of logical closure. Also, the paper includes reminiscences and reflections concerning the author's conversations with J. R. Myhill, as well as elements of the author's intellectual biography. An exceptional charm of the paper lies in the absence of the conventional separation between the treatment of personal and logical aspects of the subject.