driving on from the very beginning of life, and that our resolving it into individual movements which follow separately one upon the other is to a certain extent artificial. Your impression that these concepts require further clarification is correct, but an attempt would lead to too great digression. Before we pass on, however, let us agree to call this arrest of a partial impulse in an early stage of development, a _fixation_ of the instinct. _Regression_ is the second danger of this development by stages. Even those components which have achieved a degree of progress may readily turn backward to these earlier stages. Having attained to this later and more highly developed form, the impulse is forced to a regression when it encounters great external difficulties in the exercise of its function, and accordingly cannot reach the goal which will satisfy its strivings. We can obviously assume that fixation and regression are not independent of each other. The stronger the fixations in the process of development prove to be, the more readily will the function evade external difficulties by a regression back to those fixations, and the less capable will the fully developed function be to withstand the hindrances that stand in the way of its exercise. Remember that if a people in its wandering has left large groups at certain way-stations, it is natural for those who have gone on to return to these stations if they are beaten or encounter a mighty foe. The more they have left on the way, however, the greater is their chance of defeat. For your comprehension of the neuroses it is necessary to keep in mind this connection between fixation and regression. This will give you a secure hold upon the question of the cause of neuroses--of the etiology of neuroses--which we shall soon consider.