Ergo Proxy inside of themselves: the idea that there are two personalities inside a person and noted that René Descartes' phrase ""cogito, ergo sum"" was the inspiration for it. Satō stated that they originally did not want to explicitly express the concepts of Gnosticism in the anime. However, their personal beliefs ended up reflecting the ideas of Gnosticism and realized how well these terms fit and decided to use them. At first they intended to have Vincent as the leading protagonist and Re-l as a supporting character; however, as they fleshed out her character, she became a much stronger character and began
Cogito, ergo sum one's belief in their own existence would be secure, for there is no way one could be deceived unless one existed in order to be deceived. But I have convinced myself that there is absolutely nothing in the world, no sky, no earth, no minds, no bodies. Does it now follow that I, too, do not exist? No. If I convinced myself of something [or thought anything at all], then I certainly existed. But there is a deceiver of supreme power and cunning who deliberately and constantly deceives me. In that case, I, too, undoubtedly exist, if he deceives me;