<p>I explore the relationships between Prawitz’s approach to non-monotonic proof-theoretic validity, which I call <i>reducibility semantics</i>, and a later proof-theoretic approach, that I call <i>standard base semantics</i>. I prove that, if suitable conditions are met, reducibility semantics and standard base semantics are equivalent. As a side-result, I show that a similar relation holds, albeit in a weaker way, also between reducibility semantics and a variant of standard base semantics due to Sandqvist. Finally, notions of “point-wise” soundness and completeness (called base-soundness and base-completeness) are discussed against certain known principles from the proof-theoretic literature, as well as against monotonic proof-theoretic semantics. Intuitionistic logic is proved not to be “point-wise” complete on any kind of non-monotonic proof-theoretic semantics. The way in which this result is proved, as well as the overall behaviour of “point-wise” soundness and completeness, is significantly different in the non-monotonic framework as compared to what happens in the monotonic one—where the notions at issue can be used too to prove the “point-wise” incompleteness of intuitionistic logic.</p>