 Because non-logical parameters are never held constant, many inferences can only be declared valid if they are interpreted as enthymematic, requiring supplementation in the form of “tacit” premises. For example, \(e \lt \pi\) cannot be said to follow from \(e \lt 3\) and \(3 \lt \pi\) because there are models of \(aRb\) and \(bRc\) that are not models of \(aRc\). Adding \(\forall x \forall y \forall z ((Rxy \wedge Ryz) \rightarrow Rxz)\) to the premises, however, we obtain a valid argument form.