Abstract An anonymous manuscript from the fourteenth or early fifteenth century, recently discovered, apparently transmitted Thierry of Chartres's philosophical theology to Nicholas of Cusa around 1440. Yet the author of the treatise is not endorsing Thierry's views, as both Cusanus and modern readers have assumed, but in fact is writing in order to refute them. Curiously the author never mentions Thierry's best known triad of unitas, aequalitas and conexio . But a careful comparison of the structure of the author's argument (...) to Thierry's extant works shows that the author was nevertheless quite familiar with the Breton master's writings. The reatise's author offers an incisive critique of Thierry's theory of “four modes of being“ and rejects two of the modes in particular. From this new perspective, the manuscript can be valued as the first known evidence of Thierry of Chartres's late medieval reception. (shrink)