The secondary revision of the product of dream-activity is an admirable example of the nature and pretensions of a system. There is an intellectual function in us which demands unity, connection and intelligibility from any material, whether of perception or thought, that comes within its grasp; and if, as a result of special circumstances, it is unable to establish a true connection, it does not hesitate to fabricate a false one. Systems constructed in this way are known to us not only from dreams, but also from phobias, from obsessive thinking and from delusions. The construction of systems is seen most strikingly in delusional disorders (in paranoia), where it dominates the symptomatic picture; but its occurrence in other forms of neuro-psychosis must not be overlooked. In all these cases it can be shown that a rearrangement of the psychical material has been made with a fresh aim in view; and the rearrangement may often have to be a drastic one if the outcome is to be made to appear intelligible from the point of view of the system. Thus a system is best characterized by the fact that at least two reasons can be discovered for each of its products: a reason based upon the premises of the system (a reason, then, which may be delusional) and a concealed reason, which we must judge to be the truly operative and the real one.
Freud, Sigmund. Totem and Taboo: Some Points of Agreement between the Mental Lives of Savages and Neurotics. The Standard Edition of the Complete Psychological Works of Sigmund Freud. New York: W.W. Norton, 1989, 119.