[FOM] Predicativity
Steve Newberry
stevnewb at ix.netcom.com
Wed Apr 23 05:24:55 EDT 2003
Dear Professor Tait,
I have a question about Predicativity [NOTHING to do w. L.W.]: Usually the
predicative
criterion is linked to the Ramified Theory of Types, and in particular to a
restriction
of the Comprehension Axiom something along the following lines:
C.A. is (EP)(Ax/1, ... x/k)[ P(x/1, ... x/k) <=> R(x/1, ... x/k)] where P
does not appear
in R and the type-order of R is
{ max(Ords of unbound entities appearing in R)
Ord(R) is = max { (or)
{ 1 + max(Ords of the bound variables appearing in R )
and Ord(P) = Ord(R).
It has occurred to me that we might substantially *weaken* the restriction
to the following:
{ max(Ords of unbound entities appearing in R)
Ord(R) is = max { (or)
{ 1 + max(Ords of the universally bound variables
{ appearing in R s.t. at least one such variable
{ appears in a negated literal)
and Ord(P) = Ord(R).
without compromising the predicativity [at least in Poincare's sense.]
My reasoning is as follows: No UNIVERSAL quantifier, no circularity; No
NEGATED literal,
no viciousness. No vicious-circle, no need to increment the type-order. If
my reasoning is sound, then the difficulty in obtaining GLB and LUB should
go away, as there is NO *need*
for the vicious circle in these constructs.
Admittedly, this is a rather *terse* characterization. I have no objection
to expanding on
the idea, but for at least sixty years people have been telling me that I
consistently
tend to over-explain, and so I'm *trying* to be brief.
Does any of this make sense to you?
Respectfully,
Steve Newberry
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