In this paper we use original texts written by those involved in the development of the metric system in the 18th and 19th centuries to show that many of them had the goal of establishing a system of units in cooperation with other nations and that could be implemented universally. The phrase “for all time, for all people” originates from 1799 and epitomises the international and universal ambitions of the founders of the metric system. We show how these ambitions were also the principal inspirations for those involved in the preparatory work for the Metre Convention. We include references to documents in the BIPM archives that have not been published before.