  This connection between the conditional and consequence is called residuation by analogy with the case in mathematics. Consider the connection between addition and substraction. \(a + b = c\) if and only if \(a = c - b\). The resulting \(a\) (which is \(c - b)\) is the residual, what is left of \(c\) when \(b\) is taken away. Another name for this connection is the deduction theorem.