The '''relative umpire operator''' <math>\Upsilon : (\mathbb{B}^2 \to \mathbb{B})^2 \to \mathbb{B}</math> takes two propositions of type <math>\mathbb{B}^2 \to \mathbb{B}</math> as arguments and gives the value <math>1\!</math> if and only if the first implies the second. In symbols:
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<math>\Upsilon \langle e, f \rangle = 1 \quad \operatorname{iff} \quad e \Rightarrow f.</math>