fortune and by virtue of the interrelationship linking each thing to every other (hence, also, the small to the great), find, even in the course of such humble labour, a road to the study of the great problems. It is from this point of view that I hope to enlist your interest in considering the apparently trivial errors made by normal people. I propose now that we question someone who has no knowledge of psycho-analysis as to how he explains these occurrences. His first answer is sure to be: “Oh, they are not worth any explanation; they are little accidents.” What does the man mean by this? Does he mean to maintain that there are any occurrences so small that they fail to come within the causal sequence of things, that they might as well be other than they are? Anyone thus breaking away from the determination of natural phenomena, at any single point, has thrown over the whole scientific outlook on the world (_Weltanschauung_). One may point out to him how much more consistent is the religious outlook on the world, which emphatically assures us that “not one sparrow shall fall to the ground” except God wills it. I think our friend would not be willing to follow his first answer to its logical conclusion; he would give way and say that if he were to study these things he would soon find some explanation of them. It must be a matter of slight functional disturbances, of inaccuracies of mental performance, the conditions of which could be discovered. A man who otherwise speaks correctly may make a slip of the tongue, (1) when he is tired or unwell, (2) when he is excited, or (3) when his attention is concentrated on something else. It is easy to confirm this. Slips of the tongue do indeed occur most frequently when one is tired, or has a headache, or feels an attack of migraine coming on. Forgetting proper names very often occurs in these circumstances; many people are habitually warned of the onset of an attack of migraine by the inability to recall proper names. In excitement, too, one mixes up words or even things, one performs actions erroneously[9]; and the forgetting of intentions, as well as a number of other undesigned acts, comes to the fore when one is distracted, in other words, when the attention is concentrated on other things. A familiar instance of such distraction is the professor in _Fliegende Blätter_ who forgets his umbrella and takes the wrong hat, because he is thinking of the problems which are to be the subject of his next book. We all know from our own experience how one can forget to carry out intentions or promises when something has happened in the interval that absorbs one very deeply.