  Intersection types are an essential tool in the analysis of operational and
denotational properties of lambda-terms and functional programs. Among them,
non-idempotent intersection types provide precise quantitative information
about the evaluation of terms and programs. However, unlike simple or
second-order types, intersection types cannot be considered as a logical system
because the application rule (or the intersection rule, depending on the
presentation of the system) involves a condition expressing that the proofs of
premises satisfy a very strong uniformity condition: the underlying
lambda-terms must be the same. Using earlier work introducing an indexed
version of Linear Logic, we show that non-idempotent typing can be given a
logical form in a system where formulas represent hereditarily indexed families
of intersection types.
