We may now claim to have made further progress in the understanding of errors. We not only know them to be mental phenomena in which meaning and purpose are recognizable, not only know that they arise from the mutual interference of two different intentions, but in addition we know that, for one of these intentions to be able to express itself by interfering with another, it must itself have been subject to some hindrance against its operation. It must first be itself interfered with, before it can interfere with others. Naturally this does not give us a complete explanation of the phenomena which we call errors. We see at once further questions arising, and in general we suspect that as we progress towards comprehension the more numerous will be the occasions for new questions. We might ask, for instance, why the matter does not proceed much more simply. If the intention to restrain a certain tendency instead of carrying it into effect is present in the mind, then this restraint ought to succeed, so that nothing whatever of the tendency gains expression, or else it might fail so that the restrained tendency achieves full expression. But errors are _compromise_-formations; they express part-success and part-failure for each of the two intentions; the threatened intention is neither entirely suppressed nor, apart from some instances, does it force itself through intact. We can imagine that special conditions must be present for the occurrence of such interference (or compromise)-formations, but we cannot even conjecture of what kind they may be. Nor do I think that we could discover these unknown circumstances by penetrating further into the study of errors. It will be necessary first to examine thoroughly yet other obscure fields of mental life: only the analogies to be met with there can give us courage to form those assumptions which are requisite for a more searching elucidation of errors. And one other point! To work from slight indications, as we constantly do in this field, is not without its dangers. There is a mental disorder called combinatory paranoia in which the practice of utilizing such small indications is carried beyond all limits, and I naturally do not contend that the conclusions which are built up on such a basis are throughout correct. Only by the breadth of our observations, by the accumulation of similar impressions from the most varied forms of mental life, can we guard against this danger.