The discovery by Richard Serjeantson in 2011 of a previously unknown, early manuscript draft of the Regulae in Cambridge University Library was a hugely significant event in Cartesian scholarship. This edition presents the Cambridge manuscript of the Regulae alongside the 1701 Amsterdam version of the text to allow comparison between the early manuscript draft and the version best-known to modern readers, together with a full English translations of both texts. It is also the first critical edition of the Regulae to take into account the full range of textual witnesses to the text, both manuscript and printed.