The question relative to the bad use of language is an ancient one. Certainly, it can be traced back at least to Socrates’s critique of the sophists in Plato’s dialogues. But of course this question was also present among the pre-Socratics and subsequently was to be addressed in systematic terms by Aristotle in his Organon. It is common knowledge that Aristotle’s conceptions were then recovered during the Middle Ages. From this point of view, particularly interesting is the section of the Tractatus, known as Summule logicales, by Peter of Spain, dedicated to the “fallacies.” In recent times, as we also know, the problem of bad linguistic usage was addressed by Ludwig Wittgenstein (he thematizes the “traps” of language), and by English analytical philosophy. In Italy, it has also been studied in relation to the question of social ideology reproposed in terms of “linguistic alienation.” To the critique of the bad use of language, Giovanni Vailati in Italy had already dedicated his attention. And this is an author held in high esteem by Ferruccio Rossi-Landi throughout all his work. And as emerges from publication of the Epistolario between Giovanni Vailati and Victoria Welby (which collects a part of their correspondence in English and Italian translation), Welby’s influence on Vailati was noteworthy. Here, precisely, we will concern ourselves with how Welby too contributed to a better understanding of this problem which in her research on language had a determining value.