R. Ishmael’s Rule No. 8(b) – “lelamed hefekh hadavar” – the particularizing version of “lelamed”, may be depicted as follows, since its fourth premise is (note the reversal of order of the terms, in comparison to the preceding case):
All P1 are P2 (predicatal premise).
The four premises formally yield the conclusion “All S1 are P2” (etc.).
Yet R. Ishmael draws the very opposite conclusion “Some S1 are not P2”! Why this upside down logic? Apparently, he mentally considers the premises in conflict, due to some perceived redundancy in the text, and seeks to harmonize them by excluding all S1 other than S2 from being P2. But such particularization is logically illegitimate, since there was in fact no formal conflict between the premises, and textual repetitions can hardly be considered as such. Judge for yourself.