Metamath Proof Explorer


Theorem waj-ax

Description: A single axiom for propositional calculus discovered by Mordchaj Wajsberg (Logical Works, Polish Academy of Sciences, 1977). See: Fitelson,Some recent results in algebra and logical calculi obtained using automated reasoning, 2003 (axiom W on slide 8). (Contributed by Anthony Hart, 13-Aug-2011)

Ref Expression
Assertion waj-ax φψχθχφθφθφφψ

Proof

Step Hyp Ref Expression
1 nannan φψχφψχ
2 simpr ψχχ
3 2 imim2i φψχφχ
4 pm2.27 φφχχ
5 4 anim2d φθφχθχ
6 5 expdimp φθφχθχ
7 3 6 syl5com φψχφθθχ
8 7 con3d φψχ¬θχ¬φθ
9 df-nan θχ¬θχ
10 df-nan φθ¬φθ
11 8 9 10 3imtr4g φψχθχφθ
12 nanim θχφθθχφθφθ
13 11 12 sylib φψχθχφθφθ
14 pm3.21 ψφφψ
15 14 adantr ψχφφψ
16 15 com12 φψχφψ
17 16 a2i φψχφφψ
18 nannan φφψφφψ
19 17 18 sylibr φψχφφψ
20 13 19 jca φψχθχφθφθφφψ
21 1 20 sylbi φψχθχφθφθφφψ
22 nannan φψχθχφθφθφφψφψχθχφθφθφφψ
23 21 22 mpbir φψχθχφθφθφφψ