Everyone of us who can look back over a longer or shorter life experience will probably say that he might have spared himself many disappointments and painful surprises if he had found the courage and decision to interpret as omens the little mistakes which he made in his intercourse with people, and to consider them as indications of the intentions which were still being kept secret. As a rule, one does not dare do this. One would feel as though he were again becoming superstitious via a detour through science. But not all omens come true, and you will understand from our theories that they need not all come true. FOURTH LECTURE THE PSYCHOLOGY OF ERRORS--(_Conclusion_) We may certainly put it down as the conclusion of our labors up to this point that errors have a meaning, and we may make this conclusion the basis of our further investigations. Let me stress the fact once more that we do not assert--and for our purposes need not assert--that every single mistake which occurs is meaningful, although I consider that probable. It will suffice us if we prove the presence of such a meaning with relative frequency in the various forms of errors. These various forms, by the way, behave differently in this respect. In the cases of tongue slips, pen slips, etc., the occurrences may take place on a purely physiological basis. In the group based on forgetfulness (forgetting names or projects, mislaying objects, etc.) I cannot believe in such a basis. There does very probably exist a type of case in which the loss of objects should be recognized as unintentional. Of the mistakes which occur in daily life, only a certain portion can in any way be brought within our conception. You must keep this limitation in mind when we start henceforth from the assumption that mistakes are psychic acts and arise through the mutual interference of two intentions. Herein we have the first result of psychoanalysis. Psychology hitherto knew nothing of the occurrence of such interferences and the possibility that they might have such manifestations as a consequence. We have widened the province of the world of psychic phenomena quite considerably, and have brought into the province of psychology phenomena which formerly were not attributed to it.