"The conversion of the latent dream thoughts into those manifest deserves our close study as the first known example of the transformation of psychical stuff from one mode of expression into another. From a mode of expression which moreover is readily intelligible into another which we can only penetrate by effort and with guidance although this new mode must be equally reckoned as an effort of our own psychical activity. From the standpoint of the relationship of latent to manifest dream-content dreams can be divided into three classes. We can in the first place distinguish those dreams which have a meaning and are at the same time intelligible which allow us to penetrate into our psychical life without further ado. Such dreams are numerous; they are usually short and as a general rule do not seem very noticeable because everything remarkable or exciting surprise is absent. Their occurrence is moreover a strong argument against the doctrine which derives the dream from the isolated activity of certain cortical elements. All signs of a lowered or subdivided psychical activity are wanting. Yet we never raise any objection to characterizing them as dreams nor do we confound them with the products of our waking life."