Dreams in the second millennium B.C.E. were similar to dreams in Homerís Greece in that they were viewed as profound and important visions.   Key differences, however, do exist in the phylogenies or classification systems of the two periods.  Some works which are available from these time periods imply an inherent, virtually unchangeable system by which the dreams are divided into two categories.  The classifications in which the various dreams are placed are not conducive to the interpretation of dreams because the accepted phylogeny predetermines which dreams merit consideration.     These phylogenies can thus be seen as restrictive to the way in which the dreams are interpreted.
      The system of classification is visually apparent in The Egyptian Dream Book.  This book, dating to 2000 B.C.E., contains basically two sections and thus two phylogenies.  The first classification is good dreams and the second is bad dreams.  The left-hand column lists what a man sees himself doing in a dream, and the right-hand column says what this prophesizes.  Every dream listed is classified as either good or bad.  There is no possible category set up for a dream which is neither good nor bad.
      The restrictions which the phylogenies place on the interpretation are profound.  It is analogous to being required to describe the personalities of several people, but one can only classify them as good or bad.  No middle ground is left for people who have both qualities, or for personality traits which are neither completely good nor bad.  In this dream book, only dreams which can neatly fit into this binary classification system will be included.  While this does serve to simplify the interpretation of the dreams, it also creates a paradigm in which only certain types of dreams can fit.
    This restrictive nature can also be seen, though less profoundly, in the Babylonian-Assyrian Dream Book.  This book is set up completely in "if" and "then" statements.  This  creates a similar phylogeny in which the "then" statement basically tells the reader whether the dream is good or bad.  Similarly to the Egyptian text, this simplistic form and means of classification is restrictive to the interpretation of dreams.  Only dreams which can nicely fit into this form of "if" and "then" statements will be included.(see Oppenheim, pg. 184)
      A completely different, yet similarly restrictive, phylogeny is seen in Homerís works, The Iliad and The Odyssey.  The phylogeny which is portrayed here is not one of good versus bad, but rather a classification of true dreams versus untrue dreams.  Every dream is seen as prophetic in nature.  Some of these dreams are true, some of them are basically just lies by the gods.  Penelope sums up the phylogeny by saying, "There are two gates through which the insubstantial dreams issue."(Odyssey, lines 562-563)  One gate of which Penelope speaks is the dreams which are true.  The other gate represents those dreams which are deceptive in nature.
     This binary system of classifying dreams as either true or false can be seen in Agamemnonís dream in The Iliad.  His dream, which prophesizes that the Greeks can now defeat the Trojans, is taken to be true because of his stature as a powerful king.  Nestor goes as far to say that normally a dream such as this would be taken as completely false, but, because it is Agamemnon who had the dream, it will be taken as an accurate prophecy.(Iliad, pg 22, ln. 60-88)  Again, this inhibiting classification system plays a major role in the way in which the dream is interpreted.  By saying that dreams must be either interpreted to be true or false, the phylogeny of these dreams has again determined that no middle ground exists.  There is no room under this classification for a dream which has aspects that are true and others which are not.  Dreams are shoved into one of the two categories, regardless of whether they fit.
      Parallels can definitely be drawn between the phylogenies seen in the second millennium B.C.E. and the phylogeny which can be seen in Homerís Greece.  These phylogenies are all binary and mutually exclusive in nature.  A dream which is good cannot also be bad.  A false dream cannot be true.  By restricting the number of dreams which are even able to be analyzed as well as inhibiting the actual interpretation of admissible dreams, these means of classification hinder dream interpretation.