Abstract: "We present a foundational language for distributed programming, called Lambda 5, that addresses both mobility of code and locality of resources. In order to construct our system, we appeal to the powerful propositions-as-types interpretation of logic. Specifically, we take the possible worlds of the intuitionistic modal logic IS5 to be nodes on a network, and the connectives [square] and [diamond] to reflect mobility and locality, respectively. We formulate a novel system of natural deduction for IS5, decomposing the introduction and elimination rules for [square] and [diamond], thereby allowing the corresponding programs to be more direct. We then give an operational semantics to our calculus that is type-safe, logically faithful, and computationally realistic."