. We propose a modest conservative extension to ML that allows semi-explicit higher-order polymorphism while preserving the essential properties of ML. In our proposal, the introduction of polymorphic types remains fully explicit, that is, both the introduction and the exact polymorphic type must be specified. However, the elimination of polymorphic types is now semi-implicit: only the elimination itself must be specified as the polymorphic type is inferred. This extension is particularly useful in Objective ML where polymorphism replaces subtyping. Introduction The success of the ML language is due to its combination of several attractive features. Undoubtedly, the polymorphism of ML [2] ---or polymorphism `a la ML--- with the type inference it allows, is a major advantage. The ML type system stays in close correspondence with the rules of logic, following the Curry-Howard isomorphism between types and formulas, which provides a simple intuition, and a strong type discipline. Simult...