Buried for more than forty years in a Latin text written for seminarians at the Gregorian University in Rome, Bernard Lonergan's important work on systematic theology, De Deo Trino Pars systematica, is presented here for the first time in a facing-page edition that includes the original Latin along with a precise English translation. De Deo Trino, or The Triune God, the second part of which is the pars systematica, continues a particular strand in trinitarian theology, namely, the tradition that appeals to a psychological analogy for...