Elizabeth,
 
Your query about the Cape Fear quote intrigued me, since I've seen the film
three times (besides being a fan of DeNiro, I'm a die-hard Scorcese devotee
and own a copy of the film on disc).  I vaguely remember DeNiro's character
quoting a philosopher, but will have to check again on what the quote was
(maybe this weekend, if I can remember).
 
Anyway, I thought I knew who it must be and what the spelling is: Silesius.
But I couldn't find him in any philosophy encyclopedia.  On a next-step hunch,
I went to the New Catholic Encyclopedia, and sure enough found this (in part):
 
Angelus Silesius (1624-1677)--"German mystic and religious poet of the baroque
period.... With extraordinary creative power Angelus molded the experience of
God in mystical absorption into the pointed and often paradoxical form of the
epigram, in which he fused antitheses of >visio< and >ratio<, the mystical and
the conceptual, since, to him, antithesis was the most significant expression
of the deity who reconciles and resolves all contradictions. Angelus' theme
was... God's descent to the soul: 'I am as great as God, He's as small as I
am'...  Two years before his death he published... a phantasmagoria on the four
last things, meant to terrify men into abjuring sin."
 
Now that I see myself quoting it just above, I >do< remember the Cady character
saying approximately those words at one point; the difference may only be a
matter of translation.  Certainly the philosophical thrust suggested by this
background info on Silesius is appropos of both the Cady character and an
intriguing development of Scorcese's usual themes of guilt and redemption.
Cape Fear, which has had a mixed reception at best, may eventually proved to be
more substantial in Scorcese's canon.
 
At any rate, your question's got me wanting to look up more about this mystic/
philosophy.  Hope it's got you wanting to see the film at last.  Jeff Clark