Abstract
At work a characterization of the sins of word, i.e., those transgressions in which predominated orality, to understand what was the place that was assigned occurs within a legal framework that tended to control activities individuals and the reason why he was persecuted. At first, it shows what modifications of Christian thought that allowed for specific classifications of sins were, as a result of the emergence of Thomism, and the predominance of an ethical supported by the Decalogue, he began to speak of sins in thought, word, and deed. In researching the mechanisms that the Catholic Church used to control the use of the word they are also presented. The aim was to have strict control of the word to avoid misconceptions, ideas that could break the building and doctrinal belief system from spreading. Freedom of thought, doubt or disbelief were not permissible in a scheme that sought to impose their world view and, therefore, could not allow dissent or questioning of paradigms.