Professor Nielsen was well known for his work in political, social, and moral philosophy as well as philosophy of religion, publishing 21 books and over 400 articles. About his own work, he writes:
Kai Nielsen, professor emeritus of philosophy at the University of Calgary, has died.
I have all my adult life sought to get a cogent grip on the human part of the world, to see and write things that manage to clearly articulate… a grip on how things are and, as far as that is possible, [what] could come to obtain… Would be in a significant and decent way… to be made a significant conception of life… A life that was meaningful and desirable. To have not just such a conception of such a world but to establish its fitting with reality would be a valuable thing, something that it is now far from obtaining… I speak here of a conception of a flourishing world for all where there will be no poor. I want such a world. I seek again and again in various ways to clearly and in a non-evasive way… articulate what this world would be like and how it could be achieved.
In addition to his long tenure at Calgary, Professor Nielsen also held appointments over the course of his career at Marshall College, New York University, Amherst College, Brooklyn College, the State University of New York at Binghamton, the University of Ottawa, and Concordia University. He earned his Ph.D. in philosophy in 1959 at Duke University, and was an undergraduate at the University of North Carolina, Chapel Hill.
You can browse some of his writings here, here, and here.