 Independence friendly first-order logic (a.k.a. IF first-order logic, IF logic) was introduced by Jaakko Hintikka and Gabriel Sandu in their article ‘Informational Independence as a Semantical Phenomenon’ (1989); other early sources are Hintikka’s booklet Defining Truth, the Whole Truth, and Nothing but the Truth (1991) and Sandu’s Ph.D. thesis  (1991).[3]  IF first-order logic is an extension of first-order logic, involving a specific syntactic device ‘/’ (slash, independence indicator), which has at the object language level the same effect as the meta-level modifier ‘but does not depend on’ has in the example just considered. In the notation of IF logic, the logical form of the statement that a function \(f\) is uniformly continuous would be \((\forall a)(\forall \varepsilon)(\exists \delta /\forall a)(\forall x) R\), to be contrasted with the form of the statement that \(f\) merely is continuous, \((\forall a)(\forall \varepsilon)(\exists \delta)(\forall x) R\).