 Earlier, I suggested one possible answer: perhaps the PSR itself favors maximal series over less-than-maximal series. However, as Leibniz worried mightily, if the PSR itself favors one series of things over all others, in what sense are the alternatives genuinely possible? Alternatively, if the PSR does not favor one possible series over any other – suppose more than one maximal series of Spinoza’s finite modes is possible – then what explains why this series rather than the others actually exists?