This chapter provides a basic introduction to Cambridge Platonism and its four central figures: Benjamin Whichcote (1609–83), Ralph Cudworth (1617–88), John Smith (c. 1618–52) and Henry More (c. 1614–87). Beginning with brief biographies of the Cambridge Platonists and an outline of the Civil War background to their intellectual development, the chapter then moves to a consideration of the contested nature of Cambridge Platonism in contemporary scholarship. Were Whichcote, More, Cudworth and Smith aligned enough biographically and intellectually to warrant grouping them together as architects of a shared philosophical school of thought? After reviewing several recent arguments to the contrary, the main argument of the book is laid out: Anthony Tuckney’s 1651 correspondence with Whichcote contains important evidence that Whichcote, Cudworth, Smith and More were known to their Cambridge contemporaries as proponents of a distinctive set of philosophical positions clearly inspired by Platonism.