The Libri Carolini ("Charles' books"), more correctly Opus Caroli regis contra synodum ("The work of King Charles against the Synod"), is a work in four books composed on the command of Charlemagne in the mid 790s to refute the conclusions of the Byzantine Second Council of Nicaea (787), particularly as regards the matter of sacred images. They are "much the fullest statement of the Western attitude to representational art that has been left to us by the Middle Ages".[1]
Two earlier Frankish tracts against images (known in conjunction as the Capitulare adversus synodum) had been sent in 792 to Pope Hadrian I, who had replied with an attempt at a refutation. The Libri Carolini was then composed as a fuller rebuttal of Hadrian's position. But Charlemagne realized that further controversy with Rome would serve no purpose, and the work was never sent.
It remained unknown until it was published by Jean du Tillet in 1549, in the very different context of the debates over images at the Reformation.[2] John Calvin refers to it approvingly in later editions of his Institutes of the Christian Religion (Book 1, Ch 11, section 14), and uses it in his argument against the veneration of images.[3]