Computation of probabilities in causal models of history of science


  • Osvaldo Pessoa Jr. Depto. de Filosofia, FFLCH, USP



The aim of this paper is to investigate the ascription of probabilities in a causal model of an episode in the history of science. The aim of such a quantitative approach is to allow the implementation of the causal model in a computer, torun simulations. As an example, we look at the beginning of the science of magnetism, “explaining” — in a probabilistic way, in terms of a single causal model — why the field advanced in China but not in Europe (the difference is due to different prior probabilities of certain cultural manifestations). Given the number of years between the occurrences of two causally connected advances X and Y, one proposes a criterion for stipulating the value pY/X of the conditional probability of an advance Y occurring, given X. Next, one must assume a specific form for the cumulative probability function pY/X(t), whichwe take to be the time integral of an exponential distribution function, as is done in physics of radioactive decay. Rules for calculating the cumulative functions for more than two events are mentioned, involving composition, disjunction and conjunction of causes. We also consider the problems involved in supposing that the appearance of events in time follows an exponential distribution, which are a consequence of the fact that a composition of causes does not follow an exponential distribution, but a “hypoexponential” one. We suggestthat a gamma distribution function might more adequately represent the appearance of advances.

Author Biography

Osvaldo Pessoa Jr., Depto. de Filosofia, FFLCH, USP

Possui graduação em Física (1982) e em Filosofia (1984) pela USP, mestrado em Física Experimental pela Unicamp (1985), e doutorado em História e Filosofia da Ciência pela Indiana University (1990).