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Description: An inference version of the transitive laws for implication imim2 55 and imim1 76, which Russell and Whitehead call "the principle of the syllogism...because...the syllogism in Barbara is derived from them" (quote after Theorem *2.06 of [WhiteheadRussell] p. 101). Some authors call this law a "hypothetical syllogism". (Contributed by NM, 5-Aug-1993.) (Proof shortened by O'Cat, 20-Oct-2011.) (Proof shortened by Wolf Lammen, 26-Jul-2012.) |
Ref | Expression |
---|---|
syl.1 | |
syl.2 |
Ref | Expression |
---|---|
syl |
Step | Hyp | Ref | Expression |
---|---|---|---|
1 | syl.1 | . 2 | |
2 | syl.2 | . . 3 | |
3 | 2 | a1i 9 | . 2 |
4 | 1, 3 | mpd 13 | 1 |
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