and are wondering whether one should not forego the interpretation of such errors and let them pass for purely physiological acts, as in the days before analysis. I can imagine what it is that alarms you. My interpretation includes the assumption that tendencies of which a speaker knows nothing can express themselves through him and that I can deduce them from various indications. You hesitate before a conclusion so novel and so pregnant with consequences. I understand that, and admit that up to a point you are justified. But let one thing be clear: if you intend to carry to its logical conclusion the conception of errors which has been confirmed by so many examples, you must decide to make this startling assumption. If you cannot do this, you will have to abandon again the understanding of errors which you had only just begun to obtain. Let us pause a moment on that which unites the three groups and is common to the three mechanisms of a slip of the tongue. Fortunately this common element is unmistakable. In the first two groups the interfering tendency is admitted by the speaker; in the first, there is the additional fact that it showed itself immediately before the slip. But in both cases _it has been forced back.[24] The speaker had determined not to convert the idea into speech and then it happens that he makes a slip of the tongue; that is to say, the tendency which is debarred from expression asserts itself against his will and gains utterance, either by altering the expression of the intention permitted by him, or by mingling with it, or actually by setting itself in place of it._ This then is the mechanism of a slip of the tongue. For my own part I can bring the process in the third group also into perfect harmony with the mechanism here described. I need only assume that these three groups are differentiated by the varying degrees to which the forcing back of an intention is effective. In the first group, the intention is present and makes itself perceptible before the words are spoken; not until then does it suffer the rejection for which it indemnifies itself in the slip. In the second group the rejection reaches further back; the intention is no longer perceptible even before the speech. It is remarkable that this does not hinder it in the least from being the active cause of the slip! But this state of things simplifies the explanation of the process in the third group. I shall be bold enough to assume that a tendency can still express itself by an error though it has been debarred from expression for a long time, perhaps for a very long time, has not made itself perceptible at all, and can therefore be directly repudiated by the speaker. But leaving aside the problem of the third group, you must conclude from the other cases that _a suppression (Unterdrückung) of a previous intention to say something is the indispensable condition for the occurrence of a slip of the tongue_.