 By contrast, Bolzano’s deducibility is a relation between propositions in themselves and variable ideas. It does not rely on a strict classification of ideas as either logical or non-logical (as we saw, Bolzano had doubts about whether such a line could be drawn). Indeed, it is not a notion of logical consequence at all, but rather a more general notion of which logical consequence is a special case. Deducibility is a triadic relation involving collections of premises, conclusions, and variable ideas.