Elucida a presença do racionalismo nas tutelas de urgência e aponta para o conceito das cautelares no direito processual brasileiro. Para tanto, partiu-se do direito romano analisando os interditos e o “acontecer” da predominância da plenarização e dos juízos de certeza. Constatou-se a importância das tutelas cautelares para a sociedade contemporânea imersa em conflitos cada vez mais complexos. Conclui pela necessidade de reconhecer na tutela cautelar um direito substancial e não vincular somente sua proteção à garantia de um processo principal.; The slowness in the installment of the jurisdictional protection reveals the consequences of the inadequacy of the Brazilian procedural system. There is no doubt that the judiciary apparel with roots in the rationalism of the centuries XVIII is not capable to support the progresses and promises of the modernity. The present study elucidates the presence of the rationalism in the urgency protections and it appears for the concept of the precautionary ones in the Brazilian Procedural Law. For so much, it starts with the Roman law analyzing the injunctions and happening of the predominance of the plenary and certainty. This way, the importance of the precautionary protections was verified for the contemporary society immersed in conflicts more and more complex. Of that it occurs, the need to recognize in the precautionary protection a substantial law and not to link only his protection to the warranty of a main process.