 Hacking (1965) and Gillies offer long-run (though not infinitely long-run) propensity theories. Fetzer (1982, 1983) and Miller (1994) offer single-case propensity theories. So does Popper in a later work (1990), in which he regards propensities as “properties of the whole physical situation and sometimes of the particular way in which a situation changes” (17). Note that ‘propensities’ are categorically different things depending on which sort of theory we are considering. According to the long-run theories, propensities are tendencies to produce relative frequencies with particular values, but the propensities are not measured by the probability values themselves; according to the single-case theories, the propensities are measured by the probability values. According to Popper’s earlier view, for example, a fair die has a propensity — an extremely strong tendency — to land ‘3’ with long-run relative frequency 1/6. The small value of 1/6 does not measure this tendency. According to Giere, on the other hand, the die has a weak tendency to land ‘3’. The value of 1/6 does measure this tendency.