  Boole used the four categorical propositions as his primary forms in 1847, but in 1854 he eliminated the negative propositional forms, noting that one could change not \(y\) to not-\(y\). Thus in 1854 he would express No \(x\) is \(y\) by All \(x\) is not-\(y\), with the translation \(x = v(1-y)\), and then eliminating \(v\) to obtain 