 Algebraic structure. The two negations available in \(\mathbf{EIFL}, \neg\) and \({\sim}\), agree on true sentences, as well as on false ones: if \(\phi\) is true (false) in \(M\), then both \({\sim}\phi\) and \(\neg \phi\) are false (true) in \(M\). By contrast, if \(\phi\) is non-determined in \(M\), then \({\sim}\phi\) is non-determined as well, but \(\neg \phi\) is true. The combination \(\neg{\sim}\) of the two negations applied to a sentence \(\phi\) asserts that \(\phi\) is not  false.[66]