| Step | 
						Hyp | 
						Ref | 
						Expression | 
					
						
							| 1 | 
							
								
							 | 
							4thatleme.l | 
							 |-  .<_ = ( le ` K )  | 
						
						
							| 2 | 
							
								
							 | 
							4thatleme.j | 
							 |-  .\/ = ( join ` K )  | 
						
						
							| 3 | 
							
								
							 | 
							4thatleme.m | 
							 |-  ./\ = ( meet ` K )  | 
						
						
							| 4 | 
							
								
							 | 
							4thatleme.a | 
							 |-  A = ( Atoms ` K )  | 
						
						
							| 5 | 
							
								
							 | 
							4thatleme.h | 
							 |-  H = ( LHyp ` K )  | 
						
						
							| 6 | 
							
								
							 | 
							simp11l | 
							 |-  ( ( ( ( K e. HL /\ W e. H ) /\ ( P e. A /\ -. P .<_ W ) /\ ( Q e. A /\ -. Q .<_ W ) ) /\ ( ( R e. A /\ -. R .<_ W ) /\ S e. A ) /\ ( ( P .\/ R ) = ( Q .\/ R ) /\ P =/= Q /\ -. S .<_ ( P .\/ Q ) ) ) -> K e. HL )  | 
						
						
							| 7 | 
							
								
							 | 
							simp11 | 
							 |-  ( ( ( ( K e. HL /\ W e. H ) /\ ( P e. A /\ -. P .<_ W ) /\ ( Q e. A /\ -. Q .<_ W ) ) /\ ( ( R e. A /\ -. R .<_ W ) /\ S e. A ) /\ ( ( P .\/ R ) = ( Q .\/ R ) /\ P =/= Q /\ -. S .<_ ( P .\/ Q ) ) ) -> ( K e. HL /\ W e. H ) )  | 
						
						
							| 8 | 
							
								
							 | 
							simp12 | 
							 |-  ( ( ( ( K e. HL /\ W e. H ) /\ ( P e. A /\ -. P .<_ W ) /\ ( Q e. A /\ -. Q .<_ W ) ) /\ ( ( R e. A /\ -. R .<_ W ) /\ S e. A ) /\ ( ( P .\/ R ) = ( Q .\/ R ) /\ P =/= Q /\ -. S .<_ ( P .\/ Q ) ) ) -> ( P e. A /\ -. P .<_ W ) )  | 
						
						
							| 9 | 
							
								
							 | 
							simp13l | 
							 |-  ( ( ( ( K e. HL /\ W e. H ) /\ ( P e. A /\ -. P .<_ W ) /\ ( Q e. A /\ -. Q .<_ W ) ) /\ ( ( R e. A /\ -. R .<_ W ) /\ S e. A ) /\ ( ( P .\/ R ) = ( Q .\/ R ) /\ P =/= Q /\ -. S .<_ ( P .\/ Q ) ) ) -> Q e. A )  | 
						
						
							| 10 | 
							
								
							 | 
							simp32 | 
							 |-  ( ( ( ( K e. HL /\ W e. H ) /\ ( P e. A /\ -. P .<_ W ) /\ ( Q e. A /\ -. Q .<_ W ) ) /\ ( ( R e. A /\ -. R .<_ W ) /\ S e. A ) /\ ( ( P .\/ R ) = ( Q .\/ R ) /\ P =/= Q /\ -. S .<_ ( P .\/ Q ) ) ) -> P =/= Q )  | 
						
						
							| 11 | 
							
								1 2 3 4 5
							 | 
							lhpat | 
							 |-  ( ( ( K e. HL /\ W e. H ) /\ ( P e. A /\ -. P .<_ W ) /\ ( Q e. A /\ P =/= Q ) ) -> ( ( P .\/ Q ) ./\ W ) e. A )  | 
						
						
							| 12 | 
							
								7 8 9 10 11
							 | 
							syl112anc | 
							 |-  ( ( ( ( K e. HL /\ W e. H ) /\ ( P e. A /\ -. P .<_ W ) /\ ( Q e. A /\ -. Q .<_ W ) ) /\ ( ( R e. A /\ -. R .<_ W ) /\ S e. A ) /\ ( ( P .\/ R ) = ( Q .\/ R ) /\ P =/= Q /\ -. S .<_ ( P .\/ Q ) ) ) -> ( ( P .\/ Q ) ./\ W ) e. A )  | 
						
						
							| 13 | 
							
								
							 | 
							simp2r | 
							 |-  ( ( ( ( K e. HL /\ W e. H ) /\ ( P e. A /\ -. P .<_ W ) /\ ( Q e. A /\ -. Q .<_ W ) ) /\ ( ( R e. A /\ -. R .<_ W ) /\ S e. A ) /\ ( ( P .\/ R ) = ( Q .\/ R ) /\ P =/= Q /\ -. S .<_ ( P .\/ Q ) ) ) -> S e. A )  | 
						
						
							| 14 | 
							
								
							 | 
							simp12l | 
							 |-  ( ( ( ( K e. HL /\ W e. H ) /\ ( P e. A /\ -. P .<_ W ) /\ ( Q e. A /\ -. Q .<_ W ) ) /\ ( ( R e. A /\ -. R .<_ W ) /\ S e. A ) /\ ( ( P .\/ R ) = ( Q .\/ R ) /\ P =/= Q /\ -. S .<_ ( P .\/ Q ) ) ) -> P e. A )  | 
						
						
							| 15 | 
							
								
							 | 
							simp33 | 
							 |-  ( ( ( ( K e. HL /\ W e. H ) /\ ( P e. A /\ -. P .<_ W ) /\ ( Q e. A /\ -. Q .<_ W ) ) /\ ( ( R e. A /\ -. R .<_ W ) /\ S e. A ) /\ ( ( P .\/ R ) = ( Q .\/ R ) /\ P =/= Q /\ -. S .<_ ( P .\/ Q ) ) ) -> -. S .<_ ( P .\/ Q ) )  | 
						
						
							| 16 | 
							
								1 2 4
							 | 
							atnlej1 | 
							 |-  ( ( K e. HL /\ ( S e. A /\ P e. A /\ Q e. A ) /\ -. S .<_ ( P .\/ Q ) ) -> S =/= P )  | 
						
						
							| 17 | 
							
								6 13 14 9 15 16
							 | 
							syl131anc | 
							 |-  ( ( ( ( K e. HL /\ W e. H ) /\ ( P e. A /\ -. P .<_ W ) /\ ( Q e. A /\ -. Q .<_ W ) ) /\ ( ( R e. A /\ -. R .<_ W ) /\ S e. A ) /\ ( ( P .\/ R ) = ( Q .\/ R ) /\ P =/= Q /\ -. S .<_ ( P .\/ Q ) ) ) -> S =/= P )  | 
						
						
							| 18 | 
							
								17
							 | 
							necomd | 
							 |-  ( ( ( ( K e. HL /\ W e. H ) /\ ( P e. A /\ -. P .<_ W ) /\ ( Q e. A /\ -. Q .<_ W ) ) /\ ( ( R e. A /\ -. R .<_ W ) /\ S e. A ) /\ ( ( P .\/ R ) = ( Q .\/ R ) /\ P =/= Q /\ -. S .<_ ( P .\/ Q ) ) ) -> P =/= S )  | 
						
						
							| 19 | 
							
								1 2 3 4 5
							 | 
							lhpat | 
							 |-  ( ( ( K e. HL /\ W e. H ) /\ ( P e. A /\ -. P .<_ W ) /\ ( S e. A /\ P =/= S ) ) -> ( ( P .\/ S ) ./\ W ) e. A )  | 
						
						
							| 20 | 
							
								7 8 13 18 19
							 | 
							syl112anc | 
							 |-  ( ( ( ( K e. HL /\ W e. H ) /\ ( P e. A /\ -. P .<_ W ) /\ ( Q e. A /\ -. Q .<_ W ) ) /\ ( ( R e. A /\ -. R .<_ W ) /\ S e. A ) /\ ( ( P .\/ R ) = ( Q .\/ R ) /\ P =/= Q /\ -. S .<_ ( P .\/ Q ) ) ) -> ( ( P .\/ S ) ./\ W ) e. A )  | 
						
						
							| 21 | 
							
								2 4
							 | 
							hlsupr2 | 
							 |-  ( ( K e. HL /\ ( ( P .\/ Q ) ./\ W ) e. A /\ ( ( P .\/ S ) ./\ W ) e. A ) -> E. t e. A ( ( ( P .\/ Q ) ./\ W ) .\/ t ) = ( ( ( P .\/ S ) ./\ W ) .\/ t ) )  | 
						
						
							| 22 | 
							
								6 12 20 21
							 | 
							syl3anc | 
							 |-  ( ( ( ( K e. HL /\ W e. H ) /\ ( P e. A /\ -. P .<_ W ) /\ ( Q e. A /\ -. Q .<_ W ) ) /\ ( ( R e. A /\ -. R .<_ W ) /\ S e. A ) /\ ( ( P .\/ R ) = ( Q .\/ R ) /\ P =/= Q /\ -. S .<_ ( P .\/ Q ) ) ) -> E. t e. A ( ( ( P .\/ Q ) ./\ W ) .\/ t ) = ( ( ( P .\/ S ) ./\ W ) .\/ t ) )  | 
						
						
							| 23 | 
							
								
							 | 
							simp111 | 
							 |-  ( ( ( ( ( K e. HL /\ W e. H ) /\ ( P e. A /\ -. P .<_ W ) /\ ( Q e. A /\ -. Q .<_ W ) ) /\ ( ( R e. A /\ -. R .<_ W ) /\ S e. A ) /\ ( ( P .\/ R ) = ( Q .\/ R ) /\ P =/= Q /\ -. S .<_ ( P .\/ Q ) ) ) /\ t e. A /\ ( ( ( P .\/ Q ) ./\ W ) .\/ t ) = ( ( ( P .\/ S ) ./\ W ) .\/ t ) ) -> ( K e. HL /\ W e. H ) )  | 
						
						
							| 24 | 
							
								
							 | 
							simp112 | 
							 |-  ( ( ( ( ( K e. HL /\ W e. H ) /\ ( P e. A /\ -. P .<_ W ) /\ ( Q e. A /\ -. Q .<_ W ) ) /\ ( ( R e. A /\ -. R .<_ W ) /\ S e. A ) /\ ( ( P .\/ R ) = ( Q .\/ R ) /\ P =/= Q /\ -. S .<_ ( P .\/ Q ) ) ) /\ t e. A /\ ( ( ( P .\/ Q ) ./\ W ) .\/ t ) = ( ( ( P .\/ S ) ./\ W ) .\/ t ) ) -> ( P e. A /\ -. P .<_ W ) )  | 
						
						
							| 25 | 
							
								
							 | 
							simp113 | 
							 |-  ( ( ( ( ( K e. HL /\ W e. H ) /\ ( P e. A /\ -. P .<_ W ) /\ ( Q e. A /\ -. Q .<_ W ) ) /\ ( ( R e. A /\ -. R .<_ W ) /\ S e. A ) /\ ( ( P .\/ R ) = ( Q .\/ R ) /\ P =/= Q /\ -. S .<_ ( P .\/ Q ) ) ) /\ t e. A /\ ( ( ( P .\/ Q ) ./\ W ) .\/ t ) = ( ( ( P .\/ S ) ./\ W ) .\/ t ) ) -> ( Q e. A /\ -. Q .<_ W ) )  | 
						
						
							| 26 | 
							
								
							 | 
							simp12r | 
							 |-  ( ( ( ( ( K e. HL /\ W e. H ) /\ ( P e. A /\ -. P .<_ W ) /\ ( Q e. A /\ -. Q .<_ W ) ) /\ ( ( R e. A /\ -. R .<_ W ) /\ S e. A ) /\ ( ( P .\/ R ) = ( Q .\/ R ) /\ P =/= Q /\ -. S .<_ ( P .\/ Q ) ) ) /\ t e. A /\ ( ( ( P .\/ Q ) ./\ W ) .\/ t ) = ( ( ( P .\/ S ) ./\ W ) .\/ t ) ) -> S e. A )  | 
						
						
							| 27 | 
							
								
							 | 
							simp2ll | 
							 |-  ( ( ( ( K e. HL /\ W e. H ) /\ ( P e. A /\ -. P .<_ W ) /\ ( Q e. A /\ -. Q .<_ W ) ) /\ ( ( R e. A /\ -. R .<_ W ) /\ S e. A ) /\ ( ( P .\/ R ) = ( Q .\/ R ) /\ P =/= Q /\ -. S .<_ ( P .\/ Q ) ) ) -> R e. A )  | 
						
						
							| 28 | 
							
								27
							 | 
							3ad2ant1 | 
							 |-  ( ( ( ( ( K e. HL /\ W e. H ) /\ ( P e. A /\ -. P .<_ W ) /\ ( Q e. A /\ -. Q .<_ W ) ) /\ ( ( R e. A /\ -. R .<_ W ) /\ S e. A ) /\ ( ( P .\/ R ) = ( Q .\/ R ) /\ P =/= Q /\ -. S .<_ ( P .\/ Q ) ) ) /\ t e. A /\ ( ( ( P .\/ Q ) ./\ W ) .\/ t ) = ( ( ( P .\/ S ) ./\ W ) .\/ t ) ) -> R e. A )  | 
						
						
							| 29 | 
							
								
							 | 
							simp2lr | 
							 |-  ( ( ( ( K e. HL /\ W e. H ) /\ ( P e. A /\ -. P .<_ W ) /\ ( Q e. A /\ -. Q .<_ W ) ) /\ ( ( R e. A /\ -. R .<_ W ) /\ S e. A ) /\ ( ( P .\/ R ) = ( Q .\/ R ) /\ P =/= Q /\ -. S .<_ ( P .\/ Q ) ) ) -> -. R .<_ W )  | 
						
						
							| 30 | 
							
								29
							 | 
							3ad2ant1 | 
							 |-  ( ( ( ( ( K e. HL /\ W e. H ) /\ ( P e. A /\ -. P .<_ W ) /\ ( Q e. A /\ -. Q .<_ W ) ) /\ ( ( R e. A /\ -. R .<_ W ) /\ S e. A ) /\ ( ( P .\/ R ) = ( Q .\/ R ) /\ P =/= Q /\ -. S .<_ ( P .\/ Q ) ) ) /\ t e. A /\ ( ( ( P .\/ Q ) ./\ W ) .\/ t ) = ( ( ( P .\/ S ) ./\ W ) .\/ t ) ) -> -. R .<_ W )  | 
						
						
							| 31 | 
							
								
							 | 
							simp131 | 
							 |-  ( ( ( ( ( K e. HL /\ W e. H ) /\ ( P e. A /\ -. P .<_ W ) /\ ( Q e. A /\ -. Q .<_ W ) ) /\ ( ( R e. A /\ -. R .<_ W ) /\ S e. A ) /\ ( ( P .\/ R ) = ( Q .\/ R ) /\ P =/= Q /\ -. S .<_ ( P .\/ Q ) ) ) /\ t e. A /\ ( ( ( P .\/ Q ) ./\ W ) .\/ t ) = ( ( ( P .\/ S ) ./\ W ) .\/ t ) ) -> ( P .\/ R ) = ( Q .\/ R ) )  | 
						
						
							| 32 | 
							
								28 30 31
							 | 
							3jca | 
							 |-  ( ( ( ( ( K e. HL /\ W e. H ) /\ ( P e. A /\ -. P .<_ W ) /\ ( Q e. A /\ -. Q .<_ W ) ) /\ ( ( R e. A /\ -. R .<_ W ) /\ S e. A ) /\ ( ( P .\/ R ) = ( Q .\/ R ) /\ P =/= Q /\ -. S .<_ ( P .\/ Q ) ) ) /\ t e. A /\ ( ( ( P .\/ Q ) ./\ W ) .\/ t ) = ( ( ( P .\/ S ) ./\ W ) .\/ t ) ) -> ( R e. A /\ -. R .<_ W /\ ( P .\/ R ) = ( Q .\/ R ) ) )  | 
						
						
							| 33 | 
							
								
							 | 
							3simpc | 
							 |-  ( ( ( ( ( K e. HL /\ W e. H ) /\ ( P e. A /\ -. P .<_ W ) /\ ( Q e. A /\ -. Q .<_ W ) ) /\ ( ( R e. A /\ -. R .<_ W ) /\ S e. A ) /\ ( ( P .\/ R ) = ( Q .\/ R ) /\ P =/= Q /\ -. S .<_ ( P .\/ Q ) ) ) /\ t e. A /\ ( ( ( P .\/ Q ) ./\ W ) .\/ t ) = ( ( ( P .\/ S ) ./\ W ) .\/ t ) ) -> ( t e. A /\ ( ( ( P .\/ Q ) ./\ W ) .\/ t ) = ( ( ( P .\/ S ) ./\ W ) .\/ t ) ) )  | 
						
						
							| 34 | 
							
								
							 | 
							simp132 | 
							 |-  ( ( ( ( ( K e. HL /\ W e. H ) /\ ( P e. A /\ -. P .<_ W ) /\ ( Q e. A /\ -. Q .<_ W ) ) /\ ( ( R e. A /\ -. R .<_ W ) /\ S e. A ) /\ ( ( P .\/ R ) = ( Q .\/ R ) /\ P =/= Q /\ -. S .<_ ( P .\/ Q ) ) ) /\ t e. A /\ ( ( ( P .\/ Q ) ./\ W ) .\/ t ) = ( ( ( P .\/ S ) ./\ W ) .\/ t ) ) -> P =/= Q )  | 
						
						
							| 35 | 
							
								
							 | 
							simp133 | 
							 |-  ( ( ( ( ( K e. HL /\ W e. H ) /\ ( P e. A /\ -. P .<_ W ) /\ ( Q e. A /\ -. Q .<_ W ) ) /\ ( ( R e. A /\ -. R .<_ W ) /\ S e. A ) /\ ( ( P .\/ R ) = ( Q .\/ R ) /\ P =/= Q /\ -. S .<_ ( P .\/ Q ) ) ) /\ t e. A /\ ( ( ( P .\/ Q ) ./\ W ) .\/ t ) = ( ( ( P .\/ S ) ./\ W ) .\/ t ) ) -> -. S .<_ ( P .\/ Q ) )  | 
						
						
							| 36 | 
							
								
							 | 
							biid | 
							 |-  ( ( ( ( K e. HL /\ W e. H ) /\ ( P e. A /\ -. P .<_ W ) /\ ( Q e. A /\ -. Q .<_ W ) ) /\ ( S e. A /\ ( R e. A /\ -. R .<_ W /\ ( P .\/ R ) = ( Q .\/ R ) ) /\ ( t e. A /\ ( ( ( P .\/ Q ) ./\ W ) .\/ t ) = ( ( ( P .\/ S ) ./\ W ) .\/ t ) ) ) /\ ( P =/= Q /\ -. S .<_ ( P .\/ Q ) ) ) <-> ( ( ( K e. HL /\ W e. H ) /\ ( P e. A /\ -. P .<_ W ) /\ ( Q e. A /\ -. Q .<_ W ) ) /\ ( S e. A /\ ( R e. A /\ -. R .<_ W /\ ( P .\/ R ) = ( Q .\/ R ) ) /\ ( t e. A /\ ( ( ( P .\/ Q ) ./\ W ) .\/ t ) = ( ( ( P .\/ S ) ./\ W ) .\/ t ) ) ) /\ ( P =/= Q /\ -. S .<_ ( P .\/ Q ) ) ) )  | 
						
						
							| 37 | 
							
								
							 | 
							eqid | 
							 |-  ( ( P .\/ Q ) ./\ W ) = ( ( P .\/ Q ) ./\ W )  | 
						
						
							| 38 | 
							
								
							 | 
							eqid | 
							 |-  ( ( P .\/ S ) ./\ W ) = ( ( P .\/ S ) ./\ W )  | 
						
						
							| 39 | 
							
								
							 | 
							eqid | 
							 |-  ( ( Q .\/ t ) ./\ ( P .\/ S ) ) = ( ( Q .\/ t ) ./\ ( P .\/ S ) )  | 
						
						
							| 40 | 
							
								
							 | 
							eqid | 
							 |-  ( ( R .\/ t ) ./\ ( P .\/ S ) ) = ( ( R .\/ t ) ./\ ( P .\/ S ) )  | 
						
						
							| 41 | 
							
								36 1 2 3 4 5 37 38 39 40
							 | 
							4atexlemex4 | 
							 |-  ( ( ( ( ( K e. HL /\ W e. H ) /\ ( P e. A /\ -. P .<_ W ) /\ ( Q e. A /\ -. Q .<_ W ) ) /\ ( S e. A /\ ( R e. A /\ -. R .<_ W /\ ( P .\/ R ) = ( Q .\/ R ) ) /\ ( t e. A /\ ( ( ( P .\/ Q ) ./\ W ) .\/ t ) = ( ( ( P .\/ S ) ./\ W ) .\/ t ) ) ) /\ ( P =/= Q /\ -. S .<_ ( P .\/ Q ) ) ) /\ ( ( Q .\/ t ) ./\ ( P .\/ S ) ) = S ) -> E. z e. A ( -. z .<_ W /\ ( P .\/ z ) = ( S .\/ z ) ) )  | 
						
						
							| 42 | 
							
								36 1 2 3 4 5 37 38 39
							 | 
							4atexlemex2 | 
							 |-  ( ( ( ( ( K e. HL /\ W e. H ) /\ ( P e. A /\ -. P .<_ W ) /\ ( Q e. A /\ -. Q .<_ W ) ) /\ ( S e. A /\ ( R e. A /\ -. R .<_ W /\ ( P .\/ R ) = ( Q .\/ R ) ) /\ ( t e. A /\ ( ( ( P .\/ Q ) ./\ W ) .\/ t ) = ( ( ( P .\/ S ) ./\ W ) .\/ t ) ) ) /\ ( P =/= Q /\ -. S .<_ ( P .\/ Q ) ) ) /\ ( ( Q .\/ t ) ./\ ( P .\/ S ) ) =/= S ) -> E. z e. A ( -. z .<_ W /\ ( P .\/ z ) = ( S .\/ z ) ) )  | 
						
						
							| 43 | 
							
								41 42
							 | 
							pm2.61dane | 
							 |-  ( ( ( ( K e. HL /\ W e. H ) /\ ( P e. A /\ -. P .<_ W ) /\ ( Q e. A /\ -. Q .<_ W ) ) /\ ( S e. A /\ ( R e. A /\ -. R .<_ W /\ ( P .\/ R ) = ( Q .\/ R ) ) /\ ( t e. A /\ ( ( ( P .\/ Q ) ./\ W ) .\/ t ) = ( ( ( P .\/ S ) ./\ W ) .\/ t ) ) ) /\ ( P =/= Q /\ -. S .<_ ( P .\/ Q ) ) ) -> E. z e. A ( -. z .<_ W /\ ( P .\/ z ) = ( S .\/ z ) ) )  | 
						
						
							| 44 | 
							
								23 24 25 26 32 33 34 35 43
							 | 
							syl332anc | 
							 |-  ( ( ( ( ( K e. HL /\ W e. H ) /\ ( P e. A /\ -. P .<_ W ) /\ ( Q e. A /\ -. Q .<_ W ) ) /\ ( ( R e. A /\ -. R .<_ W ) /\ S e. A ) /\ ( ( P .\/ R ) = ( Q .\/ R ) /\ P =/= Q /\ -. S .<_ ( P .\/ Q ) ) ) /\ t e. A /\ ( ( ( P .\/ Q ) ./\ W ) .\/ t ) = ( ( ( P .\/ S ) ./\ W ) .\/ t ) ) -> E. z e. A ( -. z .<_ W /\ ( P .\/ z ) = ( S .\/ z ) ) )  | 
						
						
							| 45 | 
							
								44
							 | 
							rexlimdv3a | 
							 |-  ( ( ( ( K e. HL /\ W e. H ) /\ ( P e. A /\ -. P .<_ W ) /\ ( Q e. A /\ -. Q .<_ W ) ) /\ ( ( R e. A /\ -. R .<_ W ) /\ S e. A ) /\ ( ( P .\/ R ) = ( Q .\/ R ) /\ P =/= Q /\ -. S .<_ ( P .\/ Q ) ) ) -> ( E. t e. A ( ( ( P .\/ Q ) ./\ W ) .\/ t ) = ( ( ( P .\/ S ) ./\ W ) .\/ t ) -> E. z e. A ( -. z .<_ W /\ ( P .\/ z ) = ( S .\/ z ) ) ) )  | 
						
						
							| 46 | 
							
								22 45
							 | 
							mpd | 
							 |-  ( ( ( ( K e. HL /\ W e. H ) /\ ( P e. A /\ -. P .<_ W ) /\ ( Q e. A /\ -. Q .<_ W ) ) /\ ( ( R e. A /\ -. R .<_ W ) /\ S e. A ) /\ ( ( P .\/ R ) = ( Q .\/ R ) /\ P =/= Q /\ -. S .<_ ( P .\/ Q ) ) ) -> E. z e. A ( -. z .<_ W /\ ( P .\/ z ) = ( S .\/ z ) ) )  |