The paper provides a close lecture of the arguments and methods of legal construction, employed in the extensive individual opinions written by the Justices of the Brazilian Supreme Court in the case which authorized the same sex civil union. After tracing an outline of the legal problem and his possible solutions, we analyze the individual opinions, showing their methodological syncretism, the use of legal methods and arguments in a contradictory way as well the deficiencies in the reasoning. The Justices use legal arguments, but do not meet the requirements of rationality in the decision-making. We have a rhetorical attempt that aims to satisfy the public opinion than to offer a comprehensive and coherent solution according the normative elements of the Brazilian Federal Constitution of 1988.Universidade Estadual Paulista Júlio de Mesquita Filho, Faculdade de Ciências e Letras de Araraquara, Araraquara, Rodovia Araraquara Jau Km 01, CEP 17050-790, SP, BrasilUniversidade Estadual Paulista Júlio de Mesquita Filho, Faculdade de Ciências e Letras de Araraquara, Araraquara, Rodovia Araraquara Jau Km 01, CEP 17050-790, SP, Brasil