Peter Van Inwagen argues that The Principle of Sufficient Reason (PSR) either leads to contradiction or it leads to necessitarianism. Although I agree with Van Inwagen that the relationship between the PSR and necessitarianism is close, I argue that the PSR is compatible with innocent versions of necessitarianism. In this project my main argument is that modal realism can account for the PSR and integrate it within an innocent version of necessitarianism. My main claim will be that each fact in (...) each possible world is grounded in the principle of plenitude. Also, while each fact is grounded in plenitude, it avoids rigid necessitarianism because (i) actuality is not captured by the PSR, (ii) things could be otherwise because there are other worlds, and due to the principle of recombination (iii) cardinality of possible worlds is maximized and (iv) there are no necessary connections between distinct individuals. As a result, the relationship between modal realism and the PSR is symbiotic. Through modal realism, the PSR also results as: having its scope extended to the realm of all possibilia rather than being confined to mere actuality; it solves indeterminacy problems like Leibniz’s problem of space or the hard problem of consciousness; it accounts for facts in lawless worlds etc. On the other hand, through the PSR, modal realism gets one more benefit in its inventory because it accounts for the PSR. Thus, modal realism still continues on Lewis’ paradoxical path of proving to be highly pragmatic but counterintuitive at the same time. Ultimately, even if we reject modal realism, we can use it as a model for future defenses of the PSR against rigid necessitarianism. (shrink)