A World of Propensities

This book contains two lectures - given in 1988 and 1989 respectively - which belong to Karl Popper's late work (delivered in his 87th and 88th years), most of which is still unpublished. The first (“A World of Propensities: Two New Views of Causality”) introduces a new view of causality, based on Popper's interpretation of quantum theory, yet freed of difficulty. It is a new view of the universe - a view that easily merges with the commonsense view that our will is free. Popper recounts his debt to Alfred Tarski and his view of truth as a correspondence of a statement with the facts. It is a theory of objective truth that requires us to distinguish clearly between truth and certainty. Popper also recounts his rejection of probabilistic induction and how shocked he was when Carnap followed the probability of hypotheses line in The Logical Foundations of Probability (Chicago : The University of Chicago Press, 1950). – The second lecture (“Towards an Evolutionary Theory of Knowledge”) gives a glimpse of human knowledge as it evolves from animal knowledge. Both lectures have been expanded by Popper for publication. Popper develops his latest ideas on the objective interpretation of probability and quantum phenomena, creating a new cosmology/metaphysics in which the whole of physical reality can be seen as brought about by sets of propensities, or real (but "unrealised") potentials. The propensities are like fluid fields of forces. The future is undetermined in the sense that the present consists of many propensities that, in the present, remain in the balance. Therefore, even though the future is undetermined it is not formless: its structure at the present is described by describing the set of present propensities. Each of these propensities has an objective weighting that can be associated with a probability measure that it will be realized. The weighting characterize each (individual) propensity, but they cannot be measured other than by observing the effect of a propensity over a sequence of events. Here Popper upsets the superficial view that he despised metaphysics, finds an appropriate metaphysics for his method of falsifiability, allows for non-physical things like theories and plans to influence the physical world, and relegates the frequency interpretation of probability to the measurement of objective propensities. – Preface; – A World of Propensities: Two New Views of Causality; – Toward an Evolutionary Theory of Knowledge. M.-M. V.