Well, I have not brought you here either to delude you or to conceal anything from you. True, I announced that I would give a course of lectures entitled Introductory Lectures on Psycho-Analysis; but it was no part of my purpose to play the oracle, professing to show you an easy sequence of facts, whilst carefully concealing all difficulties, filling up gaps, and glossing over doubtful points, so that you might comfortably enjoy the belief that you have learnt something new. No, it is the very fact that you are beginners that makes me anxious to show you our science as it is, with all its excrescences and crudities, the claims that it makes and the criticism to which it may give rise. I know indeed that it is the same in every science and that, especially in the beginnings, it cannot be otherwise. I know too that, in teaching other sciences, an effort is made at first to hide these difficulties and imperfections from the learner. But that cannot be done in psycho-analysis. So I really have set up two hypotheses, the one within the other; and anyone who finds it all too laborious, or too uncertain, or who is used to higher degrees of certainty, or to more refined deductions, need go no further with me. Only I should advise him to leave psychological problems altogether alone, for it is to be feared that this is a field in which he will find no access to such exact and sure paths as he is prepared to tread. And, further, it is quite superfluous for any science which can offer a real contribution to knowledge to strive to make itself heard and to win adherents. Its reception must depend upon its results, and it can afford to wait until these have compelled attention. But I may warn those of you who are not to be deterred in this way that my two assumptions are not of equal importance. The first, that dreams are a mental phenomenon, is the hypothesis which we hope to prove by the results of our work. The second has already been proved in a different field, and I am merely taking the liberty of transferring it thence to our problems. Where, and in what connection, is it supposed to have been proved that a man can possess knowledge without knowing that he does so, which is the assumption we are making of the dreamer? Surely that would be a remarkable and surprising fact, which would change our conception of mental life and would have no need of concealment. Incidentally, it would be a fact belied in the very statement of it, which yet attempts to be literally true—a contradiction in terms. There is not, however, any attempt at concealment. We cannot blame the fact for people’s ignorance of it, or lack of interest in it, any more than we ourselves are to blame because all these psychological problems have been passed in judgement by persons who have held aloof from all the observations and experiments which alone can be conclusive.