The works of ethics developed by Peter Abelard had, despite the reasoning in Aristotelian logic, strong Platonic infuence. Among the ethical discussions of Abelard, highlight those related to cosmology of Plato’s Timaeus. The involucrum, for example, was a topic of relevance to ethics, it serves to attest to the link between the Platonic cosmology and Christian doctrine. The involucrum concerns the assumption that the revelation then would have been manifested among the pagan philosophers before the advent of Christianity and it was for the Christian philosopher uncover what was covered. Thus, one could justify the study of pagan philosophy, because its truths would then be tuned to the precepts of Christianity. This article aims to discuss the thesis of involucrum, with regard to its meaning in the thought of Abelard, particularly with regard to the concepts of Trinity and faith, both convicted in the councils of Soisson in 1121 and Sens in 1140.