  Factorizability is commonly motivated as a locality condition. In non-local models of the EPR/B experiment, the correlations between the distant outcomes are accounted for by non-local influences between the distant measurement events. For example, in orthodox quantum mechanics the first spin measurement on, say, the L-particle causes an immediate change in the spin properties of the R-particle and in the probabilities of future outcomes of spin measurements on this particle. By contrast, in local models of this experiment the correlations are supposed to be accounted for by a common cause—the pair's state λ (see Fig. 2 below): The pair's state and the L-setting determine the probability of the L-outcome; the pair's state and the R-setting determine the probability of the R-outcome; and the pair's state and the L- and the R-setting determine the probability of joint outcomes, which (as mentioned above) is simply the product of these single probabilities. The idea is that the probability of each of the outcomes is determined by ‘local events,’ i.e., events that are confined to its backward light-cone, and which can only exert subluminal or luminal influences on it (see Figure 3 below); and the distant outcomes are fundamentally independent of each other, and thus their joint probability factorizes. (For more about this reasoning, see sections 6 and 8-9.)