  The project was given an essential boost when Brady confirmed the non-triviality of the theory in the late 70s, i.e., that there are (absurd) sentences that cannot be proved in this theory, results which appeared as Brady (1989); see (Brady 2006). Further work in relevant arithmetic, by Routley, Meyer, Mortensen, Dunn, Priest, Restall, and others, followed. This led to the area now known as inconsistent mathematics, carried forward especially by Mortensen (1995, 2010), where e.g., the Routley star is used as a functor to great effect; see the entry on inconsistent mathematics for further references.