KARL POPPER
THREE WORLDS*
I
In this lecture I intend to challenge those who uphold a monist
or even a dualist view of the universe, and I will propose,
instead, a pluralist view. I will propose a view of the universe
that recognises at least three different but interacting sub-uni1
verses.
There is, first, the world that consists of physical bodies, of
stones and of stars, of plants and animals, of radiation, and of
other forms of physical energy. I will call this physical world
world 1,.
If we so wish, we can subdivide the physical world 1 into
the world of non-living physical objects and into the world of
living things, of biological objects; though we risk that the
distinction is not sharp.
There is, secondly, the mental or psychological world, the
world of our feelings of pain and pleasure, of our thoughts, of
our decisions, of our perceptions and our observations; in other
words, the world of mental or psychological entities, or of
subjective experiences. I will call it 'world 2'. World 2 is immensely important, especially from the human point of view
or from the moral point of view. Human suffering belongs to
* The Obert C. Tanner Lecture, delivered April 7, 1978, at The University of
Michigan. @ K. R. Popper 1978.
'For a fuller discussion of these ideas, see my Objective Knowledge, Clarendon
Press, Oxford, 1972, 1979; my Autobiography in P. A. Schlipp (ed.), The Philosophy
of Karl Popper, Open Court, La Salle, Illinois, 1974, also published as Unended
Quest, Fontana/Collins, London, and Open Court, La Salle, 1976; and my contributions to K. R. Popper and J. C. Eccles, The Self and Its Brain, Springer International, Berlin, Heidelberg, New York, London, 1977.
