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2.1 Language and Logic, cont.

Variable-
Binding
in L
The logic of L departs from that of conventional, single-sorted, first-order languages in its definition of variable-binding and formulation of the Quantifier Rules.  An occurrence of a variable t/t/T within a formula alpha is a bound occurrence of t/t/T in alpha if, and only if, it occurs within some part of alpha which is a formula of the form for alltbeta or of the form for sometbeta.  Otherwise, that occurrence is a free occurrence of t/t/T in alpha.  If a formula for alltbeta or for sometbeta occurs within a formula alpha (or is the formula alpha itself), then the scope in alpha of that occurrence of the quantifier for allt or for somet is the formula for alltbeta or for sometbeta itself.8
Quantifier 
Rules
in L
The rule of Universal Instantiation sanctions the move from (1) to (2),
(1) for alltpi(...ti/ti/Ti...)9
(2) pi(...tk/tk/Tk...)
where (2) results from replacing every occurrence of ti/ti/Ti free in,
(3) pi(...ti/ti/Ti...)
by occurrences of tk/tk/Tk free in (2).  UI thus sanctions the move from (4) to (5,6,7);
(4) for allwfor allx(w ex Xif-thenw ex W)
(5) for allx(w ex Xif-thenw ex W)
(6) for allx(y ex X;if-theny ex Y)
(7) for allx(z ex Xif-thenz ex Z)
in each of which generically identical, individual and haecceity variables w/W free in,
(8) for allx(w ex Xif-thenw ex W)
have been replaced by other--or perhaps the same--generically identical, individual and haecceity variables free in:
(9) for allx(w ex Tif-thent ex T)
UI does not, however, sanction the move from (4) to (10).
(10) for allx(w ex Xif-then u ex Y)
For (10) results from replacing generically identical, individual and haecceity variables w and W in (5), by the generically distinct u and Y.

The rule of Existential Instantiation sanctions the move from (11) to (12),

(11) for sometpi(...ti/ti/Ti...)
(12) pi(...tk/tk/Tk...)
where (12) results from replacing every occurrence of ti/ti/Ti free in (13),
 (13) pi(...ti/ti/Ti...)
by occurrences of tk/tk/Tk free in (12), which do not occur free in any earlier line of a proof.
cont.

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