 In this sense, e.g., the proposition [Kant is European] follows from the set {[Kant is a philosopher], [Every philosopher is German]} with respect to the idea [philosopher]. The conclusion follows, so to speak, “materially” from the premises, or is a “material” consequence of the premises, due to the fact that every German is European. This is not enough, of course, for an argument to be logically correct. In order to be logically correct, the conclusion \(s\) of an argument \(\langle \sigma , s\rangle\) must logically follow from \(\sigma\), i.e., \(s\) must be a logical consequence of \(\sigma\) (WL II, 391–395; the similarity with the distinction between material and formal consequence in Tarski 1956, 419, is obvious). A simple definition of logical consequence seems to suggest itself: \(s\) follows logically from \(\sigma\) (or: \(s\) is a logical consequence of \(\sigma)\) iff \(s\) follows from \(\sigma\) with respect to the sequence \(i^{\sigma \cup \{s\}}\) of all extra-logical simple ideas contained in \(\sigma\) or \(s\).