A surprising permanence of old motivations (a not-so-rigid story)

This is not a survey article. Rather it is a personal statement written for a lifelong friend and collaborator. Still, it is an ambition of this article to survey some of the key moments of our development in the past 40 years. In doing so perhaps some evidence has arisen which otherwise seems to be obscured by the hectic day-to-day academic life. Hence the title.