ABSTRACT
This chapter focuses on the probabilistic causality tradition initiated by I. J. Good. Probability and statistics are now used constantly within scientific theories and for the evaluation of evidence. Ian Hacking has memorably described probability as being "Janus-faced". This is after the ancient Roman god "Janus" whose name is used for our month of January. Janus had two faces looking in opposite directions, and this is true also of probability. One face of probability is the objective face. The other face of probability is the epistemic face, from the Greek epistē mē, meaning "knowledge". Judea Pearl has always interpreted the probabilities in causal networks and causal models subjectively as degrees of belief. The problem generated by the Hesslow counter-example is, as Maria Carla Galavotti observes in her 2010 work, quite similar to that of Simpson's paradox. The chapter considers the most famous example of Simpson's paradox, which concerned the seeming occurrence of gender discrimination in admission to Berkeley's graduate school.
