4 Laws and causation

Ramsey produced two theories of laws of nature (see Laws, natural). Both are Humean in distinguishing law statements from accidentally true generalizations not by what they say but by how we use them. In ‘Universals of Law and of Fact’ (1928) Ramsey says they are ‘consequences of those [general] propositions which we should take as axioms if we knew everything and organised it as simply as possible in a deductive system’ (1990a: 150). Although Ramsey soon abandoned this ‘systematic theory’ (Armstrong 1983), it remains the best Humean account of laws.

Ramsey’s second theory, in ‘General Propositions and Causality’ (1929), is that law statements like ‘all men are mortal’ are ‘variable hypotheticals’, which ‘are not judgments but rules for judging ‘‘If I meet a φ I shall regard it as a ψ’’ ’ (1990a: 149). Thus ‘a causal generalization is not … one which is simple, but one we trust’ (1990a: 150), while to believe there are unknown laws is to believe there are ‘such singular facts … as would lead us, did we know them, to assert a variable hypothetical [which must] be also asserted to hold within … the scope of our possible experience’ (1990a: 152).

This theory explains why we invoke causation and laws in assessing action, since ‘we cannot blame a man except by considering what would have happened if he had acted differently; and this … depends essentially on variable hypotheticals’ (1990a: 154). But its account of why ‘the deduction of effect from cause is conceived to be so radically different from that of cause from effect’ (1990a: 157) will not do. For here Ramsey relies on our view that causes precede their effects, a view he identifies with the fact ‘that any present volition of ours is (for us) irrelevant to any past event … to us now what we do affects only the probability of the future’ (1990a: 158; emphasis added). But this implies that the only reason we can’t affect the past is that we think we can’t, which is absurd. Only the fact, not the view, that effects never precede their causes can explain why gluttons should believe ‘I will starve if I don’t eat’ but not ‘I will have starved if I don’t eat’: pace Ramsey, some variable hypotheticals need to be made true by facts (see Causation; Counterfactual Conditionals).