Causal Laws and Effective Strategies

There are at least two kinds of laws of nature: laws of association and causal laws.1 Laws of association are the faimilar laws with which philosophers usually deal. These laws tell how often two qualities or quantities are co-associated. They may be either deterministic-the association is universal-or probabilistic. The equations of physics are a good example: whenever the force on a classical particle of mass m is f the acceleration isf/m. Laws of association may be time indexed, as in the probabilistic laws of Mendelian genetics, but apart from the asymmetries imposed by time indexing, these laws are causally neutral. They tell how often two qualities co-occur; but they provide no account of what makes things happen. Causal laws, by contrast, have the word "cause"-or some causal surrogate, right in them. Smoking causes lung cancer; perspiration attracts wood ticks; or,-for an example from physics, force causes change in motion: to quote Einstein and Infeld ([5]: 9), "The action of an external force changes the velocity... such a force either increases or decreases the velocity according to whether it acts in the direction of motion or in the opposite direction." Bertrand Russell [9] argued that laws of association are all the laws there are, and that causal principles cannot be derived from the causally symmetric laws of association. I shall here argue in support of Russell's second claim, but against the first. Causal principles cannot be reduced to laws of association; but they cannot be done away with. The argument in support of causal laws relies on some facts about strategies. They are illustrated in a letter which I recently received from TIAA-CREF, a company which provides insurance for college teachers. The letter begins: