One of the best overviews of those always-evolving, always-surprising inquiries, and especially of those Illich undertook in the incredibly fruitful later decades of his life, is a paper by his German collaborator Barbara Duden, entitled 'Ivan Illich, Beyond Medical Nemesis (1976): The Search for Modernity’s Disembodiment of “I” and “You”.' It is available at the Pudel site at the University of Bremen and at several other places around the Web.
For anyone interested in Illich, and especially if they've read his early books such as Deschooling Society or Medical Nemesis, this paper is as indispensable as David Cayley's two books: Ivan Illich in Conversation and The Rivers North of the Future.
Duden wrote this paper - her original text, in German, is also available at the Pudel site - as part of her contributions to a symposium on Illich that was held in Bremen in Feb., 2003, just more than one year after his death.
Her introductory paragraphs offer a good taste of the paper's tone of continuing wonder and heartfelt appreciation:
The many obituaries of Ivan Illich’s life and work had one thing in common: they suggest that by the end of the 1970s his hold on the public imagination had grown faint. It is as if his life and thinking stopped there. Almost all of these posthumous testimonials focus on the period between the 1950s and the late 1970s; they describe the unparalleled challenge that Ivan Illich’s “independent and catalytic thought” in the Center for Intercultural Documentation (CIDOC) presented to the vision of development nurtured by church and state. They recall Ivan’s studies of the disabling gestalt of modern institutions, his argument - hardly controversial any more - that modern institutions alienate a majority of people from the goals for which they had been planned, created, and financed. With growing intensity they instead place their consumers at an unbridgeable distance from that goal: compulsory schooling had derailed our capacity to think and learn freely; the speed of our cars and the proliferation of traffic and machines had blocked our ability and desire to walk out into the world; medicine itself threatens the health of its patients; planned, standardized housing had made it difficult for us to make homes for ourselves. Occasionally an author takes a cue from Medical Nemesis, the book that secured Illich’s reputation, and lays out the three specific levels on which medicine has become a disabling profession: medical treatment harms the patient (medical iatrogenesis), the medical system has made it almost impossible to give birth, die, or be sick at home (social iatrogenesis), and in particular, through the creed that health is an attainable goal, it has destroyed our capacity for suffering and the art of dying (cultural iatrogenesis). This is how the memorial tributes have described Ivan, as the most important critic of the global development project of the postwar period, as someone who saw and uncovered the underside of that project clearly while all the world still clung to the promise of setting the world right. Finally, these memorialists never fail to mention that while Illich left the priesthood, he did not leave the church. But they did not ask what this meant.
It is not possible in my short account to lay out a complete map of Ivan’s life in these years, even to guide you fleetingly around all the crucial corners he turned and on to all the paths he traversed. It would also be premature. [...] I spent a long night thinking about how best to characterize the fruit of these years and, in the end, three insights emerged that I would like to comment.
First, the enormously wide range of subjects that he pursued simply astounds me, themes that led him again and again into new terrains. Second, the many memorial tributes summing up his life left me perplexed, for in paying homage to a man they saw as a social critic who went his own way, they left out the most vital thing about him. All of Ivan’s works during these last decades were deeply collaborative projects hewn from long-lasting friendships and from close work with like-minded colleagues. He inspired friends to embark on new research or propelled their projects in new directions; these in turn furnished new material for Ivan’s own thinking, insights that he would weave into his own work. Finally, Ivan, the teacher, scholar, and author, was deeply anchored in the riches of hospitality in these last decades, held fast in the embrace of a long stream of guests and visitors.
I will now turn to some of Ivan’s major intellectual preoccupations, revisiting conversations of his peripathetic "academy" citing some of the friends whose work and ideas he struggled with and fostered. He would have been pleased if I succeed in identifying - amid the long series of subjects that he pursued - the continuous ascending spiral of his insights, the underlying pulse that drove his intellectual quest. One of his favorite metaphors for history was the image of a hemp-rope continually reinforced with new strands, in which the short segments of hemp disappear but the line holds fast and runs through times. The person writing history searches for signs of rupture, breaking points in the rope running through the past. My object here, then, is to hold fast to the twists and turns in Ivan’s thinking against the ruptures of his life and times.
The subheds of Duden's text provide a brief summary of the topics into which she delves as she reviews Illich's ever-evolving thinking:
From a Critique of Development to the “Archaeology of Modern Certainties”
Emblems that Elicit Empathy: “Life” as an Idol
The Mathematization of Speech and Conceptual Frameworks
From “Vernacular Customs” and “the Commons” into the Past as point of departure, orientation and repoussoir
The Waters of Forgetfulness: On the Historicity of “Stuff”
Mumblers in the Vineyard of the Text: A Way Station in the Quest for a History of Sense -Perception
A Call for an "Ascesis of the Gaze": A History From the Seeing Person to the Recording Eye
Beyond Medical Nemesis