 Bolzano proves some significant theorems about the narrower relation: If \(M\) is exactly deducible from \(A, B, C, \ldots\), then none \(A, B, C, \ldots, M\) is universally valid or universally invalid with respect to the variables of the deduction. Furthermore, the negation of each premise is compatible with the remaining premises. Hence, since compatibility is required for deducibility, each premise is independent of the others with respect to the variables of the deduction. In addition, it follows from a result proved by Rolf George that when a relation of exact deducibility holds, at least one of the variables must occur both within the premises and within the conclusion (George, 1983; cf. Rusnock and Šebestík, 2019, 314–5). Exact deducibility thus satisfies a condition of relevance (Stelzner, 2002).