I am not going to claim to be able to interperet the sequence that is occuring throughout pros and cons but I took it as an abstract occurence that would happen in a dream. Arabs with knives isn't a typical group an English man may find at the foot of his bed yet it may be something that symbolizes fear and lack of security in emotions. I don't think it was an ethnic prejudice Waters was displaying but possibly a portrayal of fear through people that the media or government portrays as violent or to be feared which translates into the protagonist's (waters) fear. Much like Waters comments "a gook on a bike" in ATD. Not actually a prejudice on Waters part but a comment on others narrowmindedness. I find pros and cons to be very intelligent in the way that Waters brings a dream to life... of course i could be completely off base here and im sure I will be made aware of my folly if need be.

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We don't know what the hell it is, except that it's very large and it has a purpose.
-Dr. Floyd, 2010