  According to Du Châtelet, the PSR is ‘[t]he principle on which all contingent truths depend…’ (IP §8). Given what follows, the most consistent way to interpret Du Châtelet's claim here is not to assume that the PSR picks out all contingent truths, for this is clearly the work of the PC (when that latter principle is used to identify necessary truths, with the leftovers therefore being contingent). Rather, Du Châtelet seems quite clearly to mean that the PSR explains why the contingent truths that actually obtain in the world do obtain. Thus, she seems to accept the second of Wolff's ways in which the PSR further explains aspects of possible things: the PSR acts as a “principle of becoming”. It also acts as a “principle of being” in so far as it explains essences, but it explains the essences of contingent things, while the essences of necessary things are explained by the PC for her (pace Wolff, but in keeping with Leibniz's usual approach). So, immediately after her definition of the PSR given above, she writes that: