Alongside of cognitive and practical thought, we must distinguish a reproductive, remembering thought, which in part enters into practical thought, but does not exhaust it.
This remembering is a precondition of all testing by critical thought: it follows back a given thought-process in a reversed direction, as far back, perhaps, as a perception -- once again, in contrast to practical thought, without an aim -- and, in doing so, makes use to a large extent of indications of quality. In thus following a backward direction, the process comes upon intermediate links which have hitherto been unconscious, which have left no indications of quality behind them but whose indications of quality appear subsequently. This implies that the passage of thought in itself, without any indications of quality, has left traces behind it. In some instances, indeed, it looks here as though we should only be able to guess certain stretches of the pathway because their starting- and end-points are given by indications of quality.
In any case, the reproducibility of thought-processes goes far beyond their indications of quality; they can be made conscious subsequently, though perhaps the outcome of a passage of thought leaves traces behind it more often than its intermediate stages. [CUT]
In the end, then, it becomes possible to cathect the memory of the pain in such a way that it cannot exhibit any backward flow and can release only minimal unpleasure. It is now tamed, and by a thought-facilitation strong enough to exercise a permanent effect and to produce an inhibiting action once more at every later repetition of the memory. The pathway leading to the release of unpleasure will then, owing to disuse, gradually increase its resistance: for facilitations are subject to gradual decay (forgetting). Only after this is the memory a tamed memory like any other.
It nevertheless appears that this process of subjugating the memory leaves a permanent effect on the passage of thought. Since earlier the passage of thought was disturbed every time the memory was activated and unpleasure aroused, there is a trend even now towards inhibiting the passage of thought as soon as the tamed memory generates its traces of unpleasure.