@@ -25871,6 +25871,31 @@ the definition of class equality ( ~ df-cleq ). Its forward implication
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EBGLMPORPCFAHLMN $.
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$}
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+ ${
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+ $d x z A $.
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+ $( Lemma for ~ iseqsetv-cleq . (Contributed by Wolf Lammen, 17-Aug-2025.)
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+ (Proof modification is discouraged.) $)
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+ iseqsetvlem $p |- ( E. x x = A <-> E. z z = A ) $=
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+ ( cv wceq eqeq1 cbvexvw ) ADZCEBDZCEABHICFG $.
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+
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+ $d y A $. $d y z $.
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+ $( Alternate proof of ~ iseqsetv-clel . The expression ` E. x x = A ` does
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+ not depend on a particular choice of the set variable. The proof here
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+ avoids ~ df-clab , ~ df-clel and ~ ax-8 , but instead is based on
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+ ~ ax-9 , ~ ax-ext and ~ df-cleq . In particular it still accepts
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+ ` x e. A ` being a primitive syntax term, not assuming any specific
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+ semantics (like elementhood in some form).
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+
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+ Use it in contexts where you want to avoid ~ df-clab , or you need
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+ ~ df-cleq anyway. See the alternative version , not using ~ df-cleq or
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+ ~ ax-ext or ~ ax-9 . (Contributed by Wolf Lammen, 6-Aug-2025.)
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+ (Proof modification is discouraged.) $)
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+ iseqsetv-cleq $p |- ( E. x x = A <-> E. y y = A ) $=
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+ ( vz cv wceq wex iseqsetvlem bitr4i ) AECFAGDECFDGBECFBGADCHBDCHI $.
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+ $( $j usage 'iseqsetv-cleq' avoids 'ax-8' 'ax-10' 'ax-11' 'ax-12' 'ax-13'
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+ 'df-clab'; $)
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+ $}
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+
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${
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$d ph y $. $d ps y $. $d x y $.
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$( Equivalent formulas yield equal class abstractions (closed form). This
@@ -26056,6 +26081,31 @@ the definition of class equality ( ~ df-cleq ). Its forward implication
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$( $j usage 'elex2' avoids 'ax-9' 'df-clab' 'ax-ext'; $)
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$}
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+ ${
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+ $d A x $. $d x y $.
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+ $( Weak version of ~ isset . (Contributed by BJ, 24-Apr-2024.) $)
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+ issettru $p |- ( E. x x = A <-> A e. { y | T. } ) $=
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+ ( cv wceq wex wtru cab wcel wa vextru biantru exbii dfclel bitr4i ) ADZCE
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+ ZAFQPGBHZIZJZAFCRIQTASQBAKLMACRNO $.
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+ $( $j usage 'issettru' avoids 'ax-9' 'ax-10' 'ax-11' 'ax-12' 'ax-13'
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+ 'ax-ext' 'df-cleq'; $)
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+ $}
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+
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+ ${
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+ $d x z A $. $d y z A $.
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+ $( Alternate proof of ~ iseqsetv-cleq . The expression ` E. x x = A ` does
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+ not depend on a particular choice of the set variable. Use this theorem
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+ in contexts where ~ df-cleq or ~ ax-ext is not referenced elsewhere in
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+ your proof. It is proven from a specific implementation (class builder,
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+ axiom ~ df-clab ) of the primitive term ` x e. A ` . (Contributed by
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+ BJ, 29-Apr-2019.) (Proof modification is discouraged.) $)
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+ iseqsetv-clel $p |- ( E. x x = A <-> E. y y = A ) $=
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+ ( vz cv wceq wex wtru cab wcel issettru bitr4i ) AECFAGCHDIJBECFBGADCKBDC
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+ KL $.
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+ $( $j usage 'iseqsetv-clel' avoids 'ax-9' 'ax-10' 'ax-11' 'ax-12' 'ax-13'
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+ 'ax-ext' 'df-cleq'; $)
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+ $}
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+
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${
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$d A x $. $d V x $.
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issetlem.1 $e |- x e. V $.
@@ -26086,8 +26136,8 @@ the definition of class equality ( ~ df-cleq ). Its forward implication
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by NM, 1-May-1995.) Reduce dependencies on axioms. (Revised by BJ,
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29-Apr-2019.) $)
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elisset $p |- ( A e. V -> E. x x = A ) $=
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- ( vy vz wcel cv wceq wex elissetv wtru cab vextru issetlem bitr3i sylib )
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- BCFDGBHDIZAGBHAIZDBCJQBKELZFRDBSEDMNABSEAMNOP $.
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+ ( vz wcel cv wceq wex elissetv iseqsetv-clel sylib ) BCEDFBGDHAFBGAHDBCID
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+ ABJK $.
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$( $j usage 'elisset' avoids 'ax-9' 'ax-10' 'ax-11' 'ax-12' 'ax-13'
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'ax-ext' 'df-cleq'; $)
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$}
@@ -26735,11 +26785,11 @@ generally appear in a single form (either definitional, but more often
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~ ax-11 , see ~ sbc5ALT for more details. (Revised by SN,
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2-Sep-2024.) $)
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clelab $p |- ( A e. { x | ph } <-> E. x ( x = A /\ ph ) ) $=
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- ( vy cab wcel cv wex wa elissetv exsimpl eqeq1 cbvexvw sylib wb eleq1 weq
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+ ( vy cab wcel cv wex wa elissetv exsimpl iseqsetv-cleq sylib wb eleq1 weq
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wceq wsb df-clab sb5 bitri anbi1d exbidv bitrid bitr3d exlimiv pm5.21nii
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- eqeq2 ) CABEZFZDGZCRZDHZBGZCRZAIZBHZDCUJJURUPBHUNUPABKUPUMBDUOULCLMNUMUKU
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- RODUMULUJFZUKURULCUJPUSBDQZAIZBHZUMURUSABDSVBADBTABDUAUBUMVAUQBUMUTUPAULC
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- UOUIUCUDUEUFUGUH $.
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+ eqeq2 ) CABEZFZDGZCQZDHZBGZCQZAIZBHZDCUIJUQUOBHUMUOABKBDCLMULUJUQNDULUKUI
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+ FZUJUQUKCUIOURBDPZAIZBHZULUQURABDRVAADBSABDTUAULUTUPBULUSUOAUKCUNUHUBUCUD
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+ UEUFUG $.
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$( $j usage 'clelab' avoids 'ax-11'; $)
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$( Obsolete version of ~ clelab as of 2-Sep-2024. (Contributed by NM,
@@ -69791,8 +69841,8 @@ pairs as classes (in set.mm, the Kuratowski encoding). A more
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$d ph y $. $d ps x $. $d F x y $. $d B x y $.
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ralima.x $e |- ( x = ( F ` y ) -> ( ph <-> ps ) ) $.
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$( Universal quantification under an image in terms of the base set.
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- (Contributed by Stefan O'Rear, 21-Jan-2015.) (Revised by Matthew House,
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- 14-Aug-2025.) $)
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+ (Contributed by Stefan O'Rear, 21-Jan-2015.) Reduce DV conditions.
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+ (Revised by Matthew House, 14-Aug-2025.) $)
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ralima $p |- ( ( F Fn A /\ B C_ A ) ->
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( A. x e. ( F " B ) ph <-> A. y e. B ps ) ) $=
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( wfn cdm wss cima wral wb fnfun wa cv wcel wceq wrex funfnd fndm biimpar
@@ -69802,8 +69852,8 @@ pairs as classes (in set.mm, the Kuratowski encoding). A more
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UIUJVFABNVAHUKULUM $.
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$( Existential quantification under an image in terms of the base set.
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- (Contributed by Stefan O'Rear, 21-Jan-2015.) (Revised by Matthew House,
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- 14-Aug-2025.) $)
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+ (Contributed by Stefan O'Rear, 21-Jan-2015.) Reduce DV conditions.
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+ (Revised by Matthew House, 14-Aug-2025.) $)
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rexima $p |- ( ( F Fn A /\ B C_ A ) ->
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( E. x e. ( F " B ) ph <-> E. y e. B ps ) ) $=
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( wfn wss wa wn cima wral wrex cv cfv wceq notbid dfrex2 ralima 3bitr4g )
@@ -587409,7 +587459,9 @@ with by (1) and (2a). Note that in order to prove ~ eliminable2a ,
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${
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$d A x $. $d x y $.
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- $( Lemma for ~ bj-denotes . (Contributed by BJ, 24-Apr-2024.)
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+ $( Duplicate of ~ issettru and ~ bj-issettruALTV .
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+
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+ Lemma for ~ bj-denotesALTV . (Contributed by BJ, 24-Apr-2024.)
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(Proof modification is discouraged.) $)
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bj-denoteslem $p |- ( E. x x = A <-> A e. { y | T. } ) $=
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( cv wceq wex wtru cab wcel wa vextru biantru exbii dfclel bitr4i ) ADZCE
@@ -587418,7 +587470,9 @@ with by (1) and (2a). Note that in order to prove ~ eliminable2a ,
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${
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$d x A $. $d y A $. $d x z $. $d y z $.
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- $( This would be the justification theorem for the definition of the unary
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+ $( Moved to main as ~ iseqsetv-clel and kept for the comments.
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+
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+ This would be the justification theorem for the definition of the unary
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predicate "E!" by ` |- ( ` E! ` A <-> E. x x = A ) ` which could be
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interpreted as " ` A ` exists" (as a set) or " ` A ` denotes" (in the
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sense of free logic).
@@ -587450,21 +587504,23 @@ with by (1) and (2a). Note that in order to prove ~ eliminable2a ,
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(Contributed by BJ, 29-Apr-2019.)
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(Proof modification is discouraged.) $)
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- bj-denotes $p |- ( E. x x = A <-> E. y y = A ) $=
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+ bj-denotesALTV $p |- ( E. x x = A <-> E. y y = A ) $=
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( vz cv wceq wex wtru cab wcel bj-denoteslem bitr4i ) AECFAGCHDIJBECFBGAD
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CKBDCKL $.
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- $( $j usage 'bj-denotes ' avoids 'ax-9' 'ax-10' 'ax-11' 'ax-12' 'ax-13'
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+ $( $j usage 'bj-denotesALTV ' avoids 'ax-9' 'ax-10' 'ax-11' 'ax-12' 'ax-13'
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'ax-ext' 'df-cleq'; $)
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$}
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${
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$d A x $. $d A z $. $d y z $.
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- $( Weak version of ~ isset without ~ ax-ext . (Contributed by BJ,
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+ $( Moved to main as ~ issettru and kept for the comments.
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+
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+ Weak version of ~ isset without ~ ax-ext . (Contributed by BJ,
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24-Apr-2024.) (Proof modification is discouraged.) $)
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- bj-issettru $p |- ( E. x x = A <-> A e. { y | T. } ) $=
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- ( vz cv wceq wex wtru cab wcel bj-denotes bj-denoteslem bitri ) AECFAGDEC
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- FDGCHBIJADCKDBCLM $.
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- $( $j usage 'bj-issettru ' avoids 'ax-9' 'ax-10' 'ax-11' 'ax-12' 'ax-13'
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+ bj-issettruALTV $p |- ( E. x x = A <-> A e. { y | T. } ) $=
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+ ( vz cv wceq wex wtru cab wcel iseqsetv-clel issettru bitri ) AECFAGDECFD
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+ GCHBIJADCKDBCLM $.
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+ $( $j usage 'bj-issettruALTV ' avoids 'ax-9' 'ax-10' 'ax-11' 'ax-12' 'ax-13'
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'ax-ext' 'df-cleq'; $)
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$}
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@@ -587474,8 +587530,8 @@ with by (1) and (2a). Note that in order to prove ~ eliminable2a ,
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"universal" class without ~ ax-ext . (Contributed by BJ, 24-Apr-2024.)
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(Proof modification is discouraged.) $)
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bj-elabtru $p |- ( A e. { x | T. } <-> A e. { y | T. } ) $=
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- ( vz wtru cab wcel cv wceq wex bj-denoteslem bitr3i ) CEAFGDHCIDJCEBFGDAC
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- KDBCKL $.
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+ ( vz wtru cab wcel cv wceq wex issettru bitr3i ) CEAFGDHCIDJCEBFGDACKDBCK
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+ L $.
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$( $j usage 'bj-elabtru' avoids 'ax-9' 'ax-10' 'ax-11' 'ax-12' 'ax-13'
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'ax-ext' 'df-cleq'; $)
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$}
@@ -587485,9 +587541,9 @@ with by (1) and (2a). Note that in order to prove ~ eliminable2a ,
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$( Closed form of ~ bj-issetw . (Contributed by BJ, 29-Apr-2019.)
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(Proof modification is discouraged.) $)
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bj-issetwt $p |- ( A. x ph -> ( A e. { x | ph } <-> E. y y = A ) ) $=
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- ( vz wal cab wcel cv wceq wa wex wb dfclel a1i biantrud bicomd bj-denotes
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- vexwt exbidv 3bitrd ) ABFZDABGZHZEIZDJZUEUCHZKZELZUFELZCIDJCLZUDUIMUBEDUC
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- NOUBUHUFEUBUFUHUBUGUFABESPQTUJUKMUBECDROUA $.
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+ ( vz wal cab wcel cv wceq wa wex wb dfclel a1i vexwt bicomd iseqsetv-clel
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+ biantrud exbidv 3bitrd ) ABFZDABGZHZEIZDJZUEUCHZKZELZUFELZCIDJCLZUDUIMUBE
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+ DUCNOUBUHUFEUBUFUHUBUGUFABEPSQTUJUKMUBECDROUA $.
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$( $j usage 'bj-issetwt' avoids 'ax-9' 'ax-10' 'ax-11' 'ax-12' 'ax-13'
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'ax-ext' 'df-cleq'; $)
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$}
@@ -587506,20 +587562,6 @@ with by (1) and (2a). Note that in order to prove ~ eliminable2a ,
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'ax-ext' 'df-cleq'; $)
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$}
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- ${
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- $d x A $. $d y A $. $d y V $.
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- $( Alternate proof of ~ elisset . This is essentially the same proof as
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- seen by inlining ~ bj-denotes and ~ bj-denoteslem . Use ~ elissetv
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- instead when sufficient (in particular when ` V ` is substituted for
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- ` _V ` ). (Contributed by BJ, 29-Apr-2019.)
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- (Proof modification is discouraged.) (New usage is discouraged.) $)
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- bj-elissetALT $p |- ( A e. V -> E. x x = A ) $=
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- ( vy wcel cv wceq wex elissetv bj-denotes sylib ) BCEDFBGDHAFBGAHDBCIDABJ
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- K $.
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- $( $j usage 'bj-elissetALT' avoids 'ax-9' 'ax-10' 'ax-11' 'ax-12' 'ax-13'
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- 'ax-ext' 'df-cleq'; $)
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- $}
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-
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${
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$d x A $. $d x V $.
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bj-issetiv.1 $e |- A e. V $.
@@ -588038,8 +588080,8 @@ but the latter requires a domain with at least two objects (hence uses
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as a byproduct, this dispenses with ~ ax-11 and ~ ax-13 ). (Contributed
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by BJ, 30-Apr-2019.) (Proof modification is discouraged.) $)
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bj-vtoclg1f1 $p |- ( E. y y = A -> ps ) $=
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- ( cv wceq wex bj-denotes bj-exlimmpi sylbi ) DIEJDKCIEJZCKBDCELABOCFGHMN
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- $.
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+ ( cv wceq wex iseqsetv-clel bj-exlimmpi sylbi ) DIEJDKCIEJZCKBDCELABOCFGH
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+ MN $.
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$}
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${
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