The focus in this paper is on deliberate human action. The central questions addressed are: whether purely rational choice is possible; whether choices may be induced by chance alone; or whether there is always a mixture of rationality and chance, as well as other factors such as habit, emotion, imitation and irrationality. The approach is a factualist one, upholding the view that, although human action can be explained by its antecedents, this is not incompatible with the notion of "free choice". (...) It is the actual choosing process that determines the final choice of action. Whatever the sources of the elements involved in the choosing process, the choice of action is a specific outcome created by the acting agent. It is in this choosing process and decision making that both rationality and chance enter. The conclusion is that rationality is the element which links intentionality with goal seeking and attainment, but that the actual choice is determined by a complex interactive process in which both logic and chance play a part. (shrink)

Four experiments investigated the effects of probability manipulations on the indicative four card selection task (Wason, 1966, 1968). All looked at the effects of high and low probability antecedents (p) and consequents (q) on participants' data selections when determining the truth or falsity of a conditional rule, if p then q . Experiments 1 and 2 also manipulated believability. In Experiment 1, 128 participants performed the task using rules with varied contents pretested for probability of occurrence. Probabilistic effects were observed (...) which were partly consistent with some probabilistic accounts but not with non-probabilistic approaches to selection task performance. No effects of believability were observed, a finding replicated in Experiment 2 which used 80 participants with standardised and familiar contents. Some effects in this experiment appeared inconsistent with existing probabilistic approaches. To avoid possible effects of content, Experiments 3 (48 participants) and 4 (20 participants) used abstract material. Both experiments revealed probabilistic effects. In the Discussion we examine the compatibility of these results with the various models of selection task performance. (shrink)

This essay addresses the methodology of philosophy of science and illustrates how formal and empirical methods can be fruitfully combined. Special emphasis is given to the application of experimental methods to confirmation theory and to recent work on the conjunction fallacy, a key topic in the rationality debate arising from research in cognitive psychology. Several other issue can be studied in this way. In the concluding section, a brief outline is provided of three further examples.