It may be asked whether and how far I am myself convinced of the truth of the hypotheses that have been set out in these pages. My answer would be that I am not convinced myself and that I do not seek to persuade other people to believe in them. Or, more precisely, that I do not know how far I believe in them. There is no reason as it seems to me, why the emotional factor of conviction should enter into this question at all. It is surely possible to throw oneself into a line of thought and to follow it wherever it leads out of simple scientific curiosity, or, if the reader prefers, as an advocatus diaboli, who is not on that account himself sold to the devil.
Beyond the Pleasure Principle, Sigmund Freud (tal cual me lo leyó A.)