Abstract
In this paper, I analyze the shift in Twardowski’s views between his early psychologistic theory of logic and his later anti-psychologistic theory. In particular, I point out that the interpretation suggesting that this change merely involves Twardowski enriching his ontology with products encounters a certain problem in light of his earlier views. To present this problem more precisely, I discuss the foundations of Twardowski’s theory of products, focusing on aspects relevant to the issue of psychologism. Based on this, I reconstruct Twardowski’s theory of logic and highlight where he identified the fallacy of psychologism. I contrast this reconstructed theory with Twardowski’s earlier views at key points and demonstrate that the difference between his early psychologistic theory and his later anti-psychologistic theory is a matter of a shift in emphasis rather than a significant change in the theoretical system itself, and that Twardowski himself understood it as such.