A train of thought thus incited in the Forec. may either disappear
spontaneously or continue. The former issue we conceive as follows: It
diffuses its energy through all the association paths emanating from it,
and throws the entire chain of ideas into a state of excitement which,
after lasting for a while, subsides through the transformation of the
excitement requiring an outlet into dormant energy.[1] If this first
issue is brought about the process has no further significance for the
dream formation. But other end-presentations are lurking in our
foreconscious that originate from the sources of our unconscious and
from the ever active wishes. These may take possession of the
excitations in the circle of thought thus left to itself, establish a
connection between it and the unconscious wish, and transfer to it the
energy inherent in the unconscious wish. Henceforth the neglected or
suppressed train of thought is in a position to maintain itself,
although this reinforcement does not help it to gain access to
consciousness. We may say that the hitherto foreconscious train of
thought has been drawn into the unconscious.

Other constellations for the dream formation would result if the
foreconscious train of thought had from the beginning been connected
with the unconscious wish, and for that reason met with rejection by the
dominating end-occupation; or if an unconscious wish were made active
for other--possibly somatic--reasons and of its own accord sought a
transference to the psychic remnants not occupied by the Forec. All
three cases finally combine in one issue, so that there is established
in the foreconscious a stream of thought which, having been abandoned by
the foreconscious occupation, receives occupation from the unconscious
wish.