Ralph Cudworth is known, if at all, as one of the leaders of the Cambridge Platonists, that group of scholars who drew on ancient texts, especially Plato, to re-invigorate the Christianity of their own time. His efforts to combat materialist and therefore potentially atheist philosophy were untiring, although his contemporaries were not always convinced of their orthodoxy. In particular, his Platonist views of the divine were often criticised as Arian. In this new book, based on his doctoral dissertation, Benjamin Carter sets out to show that Cudworth's writings were in fact driven by his strongly Trinitarian theology; not only was Cudworth's God Trinitarian, but his ideas about politics and ethics were also shaped by this doctrine. To make his case, Carter draws primarily on Cudworth's mammoth True intellectual system, but also on a range of manuscript sources which together present a much more rounded picture of Cudworth's thought. He argues that Cudworth sought to discredit not only atheism but also any kind of arbitrary authority, including Calvinist determinism, and his understanding of the Trinity was integral to this project. Carter then goes on to describe Cudworth's broader vision of ethical and political life, arguing that this too was underpinned by his understanding of the Trinity. The book asserts, in common with some recent scholarship, the importance attached to this doctrine in late seventeenth-century England, and it shows how the Trinity could inform all aspects of Christian philosophy. However, Carter's coverage of the broader intellectual context for these Trinitarian debates is thin, especially in the period before the 1690s, which means that it is harder to make sense of Cudworth's agenda or to locate him fully within English and continental debates. Carter seeks to link Cudworth to the Latitudinarian movement, on the grounds that they were all committed to a reasonable and ethical version of Trinitarian Christianity, but this argument is made quite briefly, and would need more elaboration to be fully convincing. Overall, Carter has helped to open up the thought of a neglected figure, and he even provides in an appendix a useful account of Cudworth's free will manuscripts. This book should help other scholars to engage more fully with Cudworth's writing and, perhaps, to flesh out and to complicate some of the arguments made in this present work.