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Theorem List for Metamath Proof Explorer - 28601-28700   *Has distinct variable group(s)
TypeLabelDescription
Statement
 
Theoremsbcim2g 28601 Distribution of class substitution over a left-nested implication. Similar to sbcimg 3045. sbcim2g 28601 is sbcim2gVD 28967 without virtual deductions and was automatically derived from sbcim2gVD 28967 using the tools program translate..without..overwriting.cmd and Metamath's minimize command. (Contributed by Alan Sare, 18-Mar-2012.) (Proof modification is discouraged.) (New usage is discouraged.)
 |-  ( A  e.  V  ->  (
 [. A  /  x ]. ( ph  ->  ( ps  ->  ch ) )  <->  ( [. A  /  x ]. ph  ->  (
 [. A  /  x ].
 ps  ->  [. A  /  x ].
 ch ) ) ) )
 
Theoremsbcbi 28602 Implication form of sbcbiiOLD 3060. sbcbi 28602 is sbcbiVD 28968 without virtual deductions and was automatically derived from sbcbiVD 28968 using the tools program translate..without..overwriting.cmd and Metamath's minimize command. (Contributed by Alan Sare, 18-Mar-2012.) (Proof modification is discouraged.) (New usage is discouraged.)
 |-  ( A  e.  V  ->  (
 A. x ( ph  <->  ps )  ->  ( [. A  /  x ]. ph  <->  [. A  /  x ].
 ps ) ) )
 
Theoremtrsbc 28603* Formula-building inference rule for class substitution, substituting a class variable for the set variable of the transitivity predicate. trsbc 28603 is trsbcVD 28969 without virtual deductions and was automatically derived from trsbcVD 28969 using the tools program translate..without..overwriting.cmd and Metamath's minimize command. (Contributed by Alan Sare, 18-Mar-2012.) (Proof modification is discouraged.) (New usage is discouraged.)
 |-  ( A  e.  V  ->  (
 [. A  /  x ].
 Tr  x  <->  Tr  A ) )
 
TheoremtruniALT 28604* The union of a class of transitive sets is transitive. Alternate proof of truni 4143. truniALT 28604 is truniALTVD 28970 without virtual deductions and was automatically derived from truniALTVD 28970 using the tools program translate..without..overwriting.cmd and Metamath's minimize command. (Contributed by Alan Sare, 18-Mar-2012.) (Proof modification is discouraged.) (New usage is discouraged.)
 |-  ( A. x  e.  A  Tr  x  ->  Tr  U. A )
 
TheoremsbcssOLD 28605 Distribute proper substitution through a subclass relation. This theorem was automatically derived from sbcssVD 28975. (Contributed by Alan Sare, 22-Jul-2012.) (Proof modification is discouraged.) (New usage is discouraged.)
 |-  ( A  e.  B  ->  (
 [. A  /  x ]. C  C_  D  <->  [_ A  /  x ]_ C  C_  [_ A  /  x ]_ D ) )
 
TheoremonfrALTlem5 28606* Lemma for onfrALT 28613. (Contributed by Alan Sare, 22-Jul-2012.) (Proof modification is discouraged.) (New usage is discouraged.)
 |-  ( [. ( a  i^i  x )  /  b ]. (
 ( b  C_  (
 a  i^i  x )  /\  b  =/=  (/) )  ->  E. y  e.  b  ( b  i^i  y )  =  (/) )  <->  ( ( ( a  i^i  x ) 
 C_  ( a  i^i 
 x )  /\  (
 a  i^i  x )  =/= 
 (/) )  ->  E. y  e.  ( a  i^i  x ) ( ( a  i^i  x )  i^i  y )  =  (/) ) )
 
TheoremonfrALTlem4 28607* Lemma for onfrALT 28613. (Contributed by Alan Sare, 22-Jul-2012.) (Proof modification is discouraged.) (New usage is discouraged.)
 |-  ( [. y  /  x ]. ( x  e.  a  /\  ( a  i^i  x )  =  (/) )  <->  ( y  e.  a  /\  ( a  i^i  y )  =  (/) ) )
 
TheoremonfrALTlem3 28608* Lemma for onfrALT 28613. (Contributed by Alan Sare, 22-Jul-2012.) (Proof modification is discouraged.) (New usage is discouraged.)
 |-  (
 ( a  C_  On  /\  a  =/=  (/) )  ->  ( ( x  e.  a  /\  -.  (
 a  i^i  x )  =  (/) )  ->  E. y  e.  ( a  i^i  x ) ( ( a  i^i  x )  i^i  y )  =  (/) ) )
 
Theoremggen31 28609* gen31 28698 without virtual deductions. (Contributed by Alan Sare, 22-Jul-2012.) (Proof modification is discouraged.) (New usage is discouraged.)
 |-  ( ph  ->  ( ps  ->  ( ch  ->  th )
 ) )   =>    |-  ( ph  ->  ( ps  ->  ( ch  ->  A. x th ) ) )
 
TheoremonfrALTlem2 28610* Lemma for onfrALT 28613. (Contributed by Alan Sare, 22-Jul-2012.) (Proof modification is discouraged.) (New usage is discouraged.)
 |-  (
 ( a  C_  On  /\  a  =/=  (/) )  ->  ( ( x  e.  a  /\  -.  (
 a  i^i  x )  =  (/) )  ->  E. y  e.  a  ( a  i^i  y )  =  (/) ) )
 
Theoremcbvexsv 28611* A theorem pertaining to the substitution for an existentially quantified variable when the substituted variable does not occur in the quantified wff. (Contributed by Alan Sare, 22-Jul-2012.) (Proof modification is discouraged.) (New usage is discouraged.)
 |-  ( E. x ph  <->  E. y [ y  /  x ] ph )
 
TheoremonfrALTlem1 28612* Lemma for onfrALT 28613. (Contributed by Alan Sare, 22-Jul-2012.) (Proof modification is discouraged.) (New usage is discouraged.)
 |-  (
 ( a  C_  On  /\  a  =/=  (/) )  ->  ( ( x  e.  a  /\  ( a  i^i  x )  =  (/) )  ->  E. y  e.  a  ( a  i^i  y )  =  (/) ) )
 
TheoremonfrALT 28613 The epsilon relation is foundational on the class of ordinal numbers. onfrALT 28613 is an alternate proof of onfr 4447. onfrALTVD 28983 is the Virtual Deduction proof from which onfrALT 28613 is derived. The Virtual Deduction proof mirrors the working proof of onfr 4447 which is the main part of the proof of Theorem 7.12 of the first edition of TakeutiZaring. The proof of the corresponding Proposition 7.12 of [TakeutiZaring] p. 38 (second edition) does not contain the working proof equivalent of onfrALTVD 28983. This theorem does not rely on the Axiom of Regularity. (Contributed by Alan Sare, 22-Jul-2012.) (Proof modification is discouraged.) (New usage is discouraged.)
 |-  _E  Fr  On
 
Theoremcsbeq2g 28614 Formula-building implication rule for class substitution. Closed form of csbeq2i 3120. csbeq2g 28614 is derived from the virtual deduction proof csbeq2gVD 28984. (Contributed by Alan Sare, 10-Nov-2012.) (Proof modification is discouraged.) (New usage is discouraged.)
 |-  ( A  e.  V  ->  (
 A. x  B  =  C  ->  [_ A  /  x ]_ B  =  [_ A  /  x ]_ C ) )
 
Theorem19.41rg 28615 Closed form of right-to-left implication of 19.41 1827, Theorem 19.41 of [Margaris] p. 90. Derived from 19.41rgVD 28994. (Contributed by Alan Sare, 8-Feb-2014.) (Proof modification is discouraged.) (New usage is discouraged.)
 |-  ( A. x ( ps  ->  A. x ps )  ->  ( ( E. x ph 
 /\  ps )  ->  E. x ( ph  /\  ps )
 ) )
 
Theoremopelopab4 28616* Ordered pair membership in a class abstraction of pairs. Compare to elopab 4288. (Contributed by Alan Sare, 8-Feb-2014.) (Revised by Mario Carneiro, 6-May-2015.) (Proof modification is discouraged.) (New usage is discouraged.)
 |-  ( <. u ,  v >.  e. 
 { <. x ,  y >.  |  ph }  <->  E. x E. y
 ( ( x  =  u  /\  y  =  v )  /\  ph )
 )
 
Theorem2pm13.193 28617 pm13.193 27714 for two variables. pm13.193 27714 is Theorem *13.193 in [WhiteheadRussell] p. 179. Derived from 2pm13.193VD 28995. (Contributed by Alan Sare, 8-Feb-2014.) (Proof modification is discouraged.) (New usage is discouraged.)
 |-  (
 ( ( x  =  u  /\  y  =  v )  /\  [ u  /  x ] [
 v  /  y ] ph )  <->  ( ( x  =  u  /\  y  =  v )  /\  ph )
 )
 
Theoremhbntal 28618 A closed form of hbn 1732. hbnt 1736 is another closed form of hbn 1732. (Contributed by Alan Sare, 8-Feb-2014.) (Proof modification is discouraged.) (New usage is discouraged.)
 |-  ( A. x ( ph  ->  A. x ph )  ->  A. x ( -.  ph  ->  A. x  -.  ph ) )
 
Theoremhbimpg 28619 A closed form of hbim 1737. Derived from hbimpgVD 28996. (Contributed by Alan Sare, 8-Feb-2014.) (Proof modification is discouraged.) (New usage is discouraged.)
 |-  (
 ( A. x ( ph  ->  A. x ph )  /\  A. x ( ps 
 ->  A. x ps )
 )  ->  A. x ( ( ph  ->  ps )  ->  A. x ( ph  ->  ps ) ) )
 
Theoremhbalg 28620 Closed form of hbal 1722. Derived from hbalgVD 28997. (Contributed by Alan Sare, 8-Feb-2014.) (Proof modification is discouraged.) (New usage is discouraged.)
 |-  ( A. y ( ph  ->  A. x ph )  ->  A. y ( A. y ph  ->  A. x A. y ph ) )
 
Theoremhbexg 28621 Closed form of nfex 1779. Derived from hbexgVD 28998. (Contributed by Alan Sare, 8-Feb-2014.) (Revised by Mario Carneiro, 12-Dec-2016.) (Proof modification is discouraged.) (New usage is discouraged.)
 |-  ( A. x A. y (
 ph  ->  A. x ph )  ->  A. x A. y
 ( E. y ph  ->  A. x E. y ph ) )
 
Theorema9e2eq 28622* Alternate form of a9e 1904 for non-distinct  x,  y and  u  =  v. a9e2eq 28622 is derived from a9e2eqVD 28999. (Contributed by Alan Sare, 25-Mar-2014.) (Proof modification is discouraged.) (New usage is discouraged.)
 |-  ( A. x  x  =  y  ->  ( u  =  v  ->  E. x E. y ( x  =  u  /\  y  =  v ) ) )
 
Theorema9e2nd 28623* If at least two sets exist (dtru 4217) , then the same is true expressed in an alternate form similar to the form of a9e 1904. a9e2nd 28623 is derived from a9e2ndVD 29000. (Contributed by Alan Sare, 25-Mar-2014.) (Proof modification is discouraged.) (New usage is discouraged.)
 |-  ( -.  A. x  x  =  y  ->  E. x E. y ( x  =  u  /\  y  =  v ) )
 
Theorema9e2ndeq 28624* "At least two sets exist" expressed in the form of dtru 4217 is logically equivalent to the same expressed in a form similar to a9e 1904 if dtru 4217 is false implies  u  =  v. a9e2ndeq 28624 is derived from a9e2ndeqVD 29001. (Contributed by Alan Sare, 25-Mar-2014.) (Proof modification is discouraged.) (New usage is discouraged.)
 |-  (
 ( -.  A. x  x  =  y  \/  u  =  v )  <->  E. x E. y ( x  =  u  /\  y  =  v )
 )
 
Theorem2sb5nd 28625* Equivalence for double substitution 2sb5 2064 without distinct  x,  y requirement. 2sb5nd 28625 is derived from 2sb5ndVD 29002. (Contributed by Alan Sare, 30-Apr-2014.) (Proof modification is discouraged.) (New usage is discouraged.)
 |-  (
 ( -.  A. x  x  =  y  \/  u  =  v )  ->  ( [ u  /  x ] [ v  /  y ] ph  <->  E. x E. y
 ( ( x  =  u  /\  y  =  v )  /\  ph )
 ) )
 
Theorem2uasbanh 28626* Distribute the unabbreviated form of proper substitution in and out of a conjunction. 2uasbanh 28626 is derived from 2uasbanhVD 29003. (Contributed by Alan Sare, 31-May-2014.) (Proof modification is discouraged.) (New usage is discouraged.)
 |-  ( ch 
 <->  ( E. x E. y ( ( x  =  u  /\  y  =  v )  /\  ph )  /\  E. x E. y
 ( ( x  =  u  /\  y  =  v )  /\  ps ) ) )   =>    |-  ( E. x E. y ( ( x  =  u  /\  y  =  v )  /\  ( ph  /\  ps ) )  <-> 
 ( E. x E. y ( ( x  =  u  /\  y  =  v )  /\  ph )  /\  E. x E. y
 ( ( x  =  u  /\  y  =  v )  /\  ps ) ) )
 
Theorem2uasban 28627* Distribute the unabbreviated form of proper substitution in and out of a conjunction. (Contributed by Alan Sare, 31-May-2014.) (Proof modification is discouraged.) (New usage is discouraged.)
 |-  ( E. x E. y ( ( x  =  u 
 /\  y  =  v )  /\  ( ph  /\ 
 ps ) )  <->  ( E. x E. y ( ( x  =  u  /\  y  =  v )  /\  ph )  /\  E. x E. y
 ( ( x  =  u  /\  y  =  v )  /\  ps ) ) )
 
Theoreme2ebind 28628 Absorption of an existential quantifier of a double existential quantifier of non-distinct variables. e2ebind 28628 is derived from e2ebindVD 29004. (Contributed by Alan Sare, 27-Nov-2014.) (Proof modification is discouraged.) (New usage is discouraged.)
 |-  ( A. x  x  =  y  ->  ( E. x E. y ph  <->  E. y ph )
 )
 
Theoremelpwgded 28629 elpwgdedVD 29009 in conventional notation. (Contributed by Alan Sare, 23-Apr-2015.) (Proof modification is discouraged.) (New usage is discouraged.)
 |-  ( ph  ->  A  e.  _V )   &    |-  ( ps  ->  A  C_  B )   =>    |-  ( ( ph  /\  ps )  ->  A  e.  ~P B )
 
Theoremtrelded 28630 Deduction form of trel 4136. In a transitive class, the membership relation is transitive. (Contributed by Alan Sare, 3-Dec-2015.) (Proof modification is discouraged.) (New usage is discouraged.)
 |-  ( ph  ->  Tr  A )   &    |-  ( ps  ->  B  e.  C )   &    |-  ( ch  ->  C  e.  A )   =>    |-  ( ( ph  /\  ps  /\ 
 ch )  ->  B  e.  A )
 
Theoremjaoded 28631 Deduction form of jao 498. Disjunction of antecedents. (Contributed by Alan Sare, 3-Dec-2015.) (Proof modification is discouraged.) (New usage is discouraged.)
 |-  ( ph  ->  ( ps  ->  ch ) )   &    |-  ( th  ->  ( ta  ->  ch )
 )   &    |-  ( et  ->  ( ps  \/  ta ) )   =>    |-  ( ( ph  /\  th  /\ 
 et )  ->  ch )
 
Theorem3imp31 28632 The importation inference 3imp 1145 with commutation of the first and third conjuncts of the assertion relative to the hypothesis. (Contributed by Alan Sare, 11-Sep-2016.) (Proof modification is discouraged.)
 |-  ( ph  ->  ( ps  ->  ( ch  ->  th )
 ) )   =>    |-  ( ( ch  /\  ps 
 /\  ph )  ->  th )
 
Theorem3imp21 28633 The importation inference 3imp 1145 with commutation of the first and second conjuncts of the assertion relative to the hypothesis. (Contributed by Alan Sare, 11-Sep-2016.) (Proof modification is discouraged.)
 |-  ( ph  ->  ( ps  ->  ( ch  ->  th )
 ) )   =>    |-  ( ( ps  /\  ph 
 /\  ch )  ->  th )
 
Theorembiimpa21 28634 biimpa 470 with commutation of the first and second conjuncts of the assertion. (Contributed by Alan Sare, 11-Sep-2016.)
 |-  ( ph  ->  ( ps  <->  ch ) )   =>    |-  ( ( ps 
 /\  ph )  ->  ch )
 
TheoremsbtT 28635 A substitution into a theorem remains true. sbt 1986 with the existence of no virtual hypotheses for the hypothesis expressed as the empty virtual hypothesis collection. (Contributed by Alan Sare, 4-Feb-2017.) (Proof modification is discouraged.) (New usage is discouraged.)
 |-  (  T.  ->  ph )   =>    |- 
 [ y  /  x ] ph
 
18.25.4  What is Virtual Deduction?
 
Syntaxwvd1 28636 A Virtual Deduction proof in a Hilbert-style deductive system is the analog of a sequent calculus proof. A theorem is proven in a Gentzen system in order to prove more directly, which may be more intuitive and easier for some people. The analog of this proof in Metamath's Hilbert-style system is verified by the Metamath program.

Natural Deduction is a well-known proof method orignally proposed by Gentzen in 1935 and comprehensively summarized by Prawitz in his 1965 monograph "Natural deduction: a proof-theoretic study". Gentzen wished to construct "a formalism that comes as close as possible to natural reasoning". Natural deduction is a response to dissatisfaction with axiomatic proofs such as Hilbert-style axiomatic proofs, which the proofs of Metamath are. In 1926, in Poland, Lukasiewicz advocated a more natural treatment of logic. Jaskowski made the earliest attempts at defining a more natural deduction. Natural deduction in its modern form was independently proposed by Gentzen.

Sequent calculus, the chief alternative to Natural Deduction, was created by Gentzen. The following is an except from Stephen Cole Kleene's seminal 1952 book "Introduction to Metamathematics", which contains the first formulation of sequent calculus in the modern style. Kleene states on page 440:

. . . the proof of (Gentzen's Hauptsatz) breaks down into a list of cases, each of which is simple to handle. . . . Gentzen's normal form for proofs in the predicate calculus requires a different classification of the deductive steps than is given by the postulates of the formal system of predicate calculus of Chapter IV (Section 19). The implication symbol  -> (the Metamath symbol for implication has been substituted here for the symbol used by Kleene) has to be separated in its role of mediating inferences from its role as a component symbol of the formula being proved. In the former role it will be replaced by a new formal symbol  ->.. (read "gives" or "entails"), to which properties will be assigned similar to those of the informal symbol  |- in our former derived rules.

Gentzen's classification of the deductive operations is made explicit by setting up a new formal system of the predicate calculus. The formal system of propositional and predicate calculus studied previously (Chapters IV ff.) we call now a "Hilbert-type system", and denote by H. Precisely, H denotes any one or a particular one of several systems, according to whether we are considering propositional calculus or predicate calculus, in the classical or the intuitionistic version (Section 23), and according to the sense in which we are using "term" and "formula" (Sections 117,25,31,37,72-76). The same respective choices will apply to the "Gentzen-type system G1" which we introduce now and the G2, G3 and G3a later.

The transformation or deductive rules of G1 will apply to objects which are not formulas of the system H, but are built from them by an additional formation rule, so we use a new term "sequent" for these objects. (Gentzen says "Sequenz", which we translate as "sequent", because we have already used "sequence" for any succession of objects, where the German is "Folge".) A sequent is a formal expression of the form  ph, . . . ,  ps  ->..  ch, . . . ,  th where  ph , . . . ,  ps and  ch, . . . ,  th are seqences of a finite number of 0 or more formulas (substituting Metamath notation for Kleene's notation). The part  ph, . . . ,  ps is the antecedent, and  ch, . . . ,  th the succedent of the sequent  ph, . . . ,  ps  ->..  ch, . . . ,  th.

When the antecedent and the succedent each have a finite number of 1 or more formulas, the sequent  ph, . . . ,  ps  ->..  ch, . . .  th has the same interpretation for G1 as the formula  ( ( ph  /\. . .  /\  ps )  ->  ( ch  \/. . .  \/  th ) ) for H. The interpretation extends to the case of an antecedent of 0 formulas by regarding  ( ph  /\. . .  /\ 
ps ) for 0 formulas (the "empty conjunction") as true and  ( ch  \/. . .  \/  th ) for 0 formulas (the "empty disjunction") as false.

. . . As in Chapter V, we use Greek capitals . . . to stand for finite sequences of zero or more formulas, but now also as antecedent (succedent), or parts of antecedent (succedent), with separating formal commas included. . . . (End of Kleene excerpt)

In chapter V entitled "Formal Deduction" Kleene states, on page 86:

Section 20. Formal deduction. Formal proofs of even quite elementary theorems tend to be long. As a price for having analyzed logical deduction into simple steps, more of those steps have to be used.

The purpose of formalizing a theory is to get an explicit definition of what constitutes proof in the theory. Having achieved this, there is no need always to appeal directly to the definition. The labor required to establish the formal provability of formulas can be greatly lessened by using metamathematical theorems concerning the existence of formal proofs. If the demonstrations of those theorems do have the finitary character which metamathematics is supposed to have, the demonstrations will indicate, at least implicitly, methods for obtaining the formal proofs. The use of the metamathematical theorems then amounts to abbreviation, often of very great extent, in the presentation of formal proofs.

The simpler of such metamathematical theorems we shall call derived rules, since they express principles which can be said to be derived from the postulated rules by showing that the use of them as additional methods of inference does not increase the class of provable formulas. We shall seek by means of derived rules to bring the methods for establishing the facts of formal provability as close as possible to the informal methods of the theory which is being formalized.

In setting up the formal system, proof was given the simplest possible structure, consisting of a single sequence of formulas. Some of our derived rules, called "direct rules", will serve to abbreviate for us whole segments of such a sequence; we can then, so to speak, use these segments as prefabricated units in building proofs.

But also, in mathematical practice, proofs are common which have a more complicated structure, employing "subsidiary deduction", i.e. deduction under assumptions for the sake of the argument, which assumptions are subsequently discharged. For example, subsidiary deduction is used in a proof by reductio ad absurdum, and less obtrusively when we place the hypothesis of a theorem on a par with proved propositions to deduce the conclusion. Other derived rules, called "subsidiary deduction rules", will give us this kind of procedure.

We now introduce, by a metamathematical definition, the notion of "formal deducibility under assumptions". Given a list  ph, . . .  ps of  0 or more (occurences of) formulas, a finite sequence of one or more (occurences of) formulas is called a (formal) deduction from the assumption formulas 
ph, . . .  ps, if each formula of the sequence is either one of the formulas  ph, . . .  ps, or an axiom, or an immediate consequence of preceding formulas of a sequence. A deduction is said to be deducible from the assumption formulas (in symbols,  ph,. . . . ,.  ps |-  ch), and is called the conclusion (or endformula) of the deduction. (The symbol  |- may be read "yields".) (End of Kleene excerpt)

Gentzen's normal form is a certain direct fashion for proofs and deductions. His sequent calculus, formulated in the modern style by Kleene, is the classical system G1. In this system, the new formal symbol  ->.. has properties similar to the informal symbol  |- of Kleene's above language of formal deducibility under assumptions.

Kleene states on page 440:

. . . This leads us to inquire whether there may not be a theorem about the predicate calculus asserting that, if a formula is provable (or deducible from other formulas), it is provable (or deducible) in a certain direct fashion; in other words, a theorem giving a normal form for proofs and deductions, the proofs and deduction in normal form being in some sense direct. (End of Kleene excerpt)

There is such a theorem, which was proven by Kleene.

Formal proofs in H of even quite elementary theorems tend to be long. As a price for having analyzed logical deduction into simple steps, more of those steps have to be used. The proofs of Metamath are fully detailed formal proofs. We wish to have a means of proving Metamath theorems and deductions in a more direct fashion. Natural Deduction is a system for proving theorems and deductions in a more direct fashion. However, Natural Deduction is not compatible for use with Metamath, which uses a Hilbert-type system. Instead, Kleene's classical system G1 may be used for proving Metamath deductions and theorems in a more direct fashion.

The system of Metamath is an H system, not a Gentzen system. Therefore, proofs in Kleene's classical system G1 ("G1") cannot be included in Metamath's system H, which we shall henceforth call "system H" or "H". However, we may translate proofs in G1 into proofs in H.

By Kleene's THEOREM 47 (page 446)

if  |-  ->..  ph in G1 then  |-  ph in H

By Kleene's COROLLARY of THEOREM 47 (page 448)

if  |-  ph  ->..  ps in G1 then  |-  (. ph  ->.  ps ). in H
if  |-  ph ,. ps  ->..  ch in G1 then  |-  (. (. ph ,. ps ).  ->.  ch ). in H
if  |-  ph ,. ps ,. ch  ->..  th in G1 then  |-  (. (. ph ,. ps ,. ch ).  ->.  th ). in H

 ->. denotes the same connective denoted by  ->. " , " , in the context of Virtual Deduction, denotes the same connective denoted by  /\. This Virtual Deduction notation is specified by the following set.mm definitions:

df-vd1 28637  |-  ( (. ph  ->.  ps ).  <->  ( ph  ->  ps ) )
dfvd2an 28650  |-  ( (. (. ph ,. ps ).  ->.  ch ).  <->  ( ( ph  /\  ps )  ->  ch ) )
dfvd3an 28662  |-  ( (. (. ph ,. ps ,. ch ).  ->.  th ).  <->  ( ( ph  /\  ps  /\  ch )  ->  th ) )

 ->. replaces 
->.. in the analog in H of a sequent in G1 having a non-empty antecedent. If  ->. occurs as the outermost connective denoted by 
->. or  -> and occurs exactly once, we call the analog in H of a sequent in G1 a "virtual deduction" because the corresponding  ->.. of the sequent is assigned properties similar to  |-.

While sequent calculus proofs (proofs in G1) may have as steps sequents with 0, 1, or more formulas in the succedent, we shall only prove in G1 using sequents with exactly 1 formula in the succedent.

The User proves in G1 in order to obtain the benefits of more direct proving using sequent calculus, then translates the proof in G1 into a proof in H. The reference theorems and deductions to be used for proving in G1 are translations of theorems and deductions in set.mm.

Each theorem  |-  ph in set.mm corresponds to the theorem  |-  ->..  ph in G1. Deductions in G1 corresponding to deductions in H are similarly determined. Theorems in H with one or more occurences of either 
->. or  -> may also be translated into theorems in G1 for by replacing the outermost occurence of  ->. or  -> of the theorem in H with  ->... Deductions in H may be translated into deductions in G1 in a similar manner. The only theorems and deductions in H useful for proving in G1 for the purpose of obtaining proofs in H are those in which, for each hypothesis or assertion, there are 0 or 1 occurences of  ->. and it is the outermost occurence of  ->. or  ->. Kleene's THEOREM 46 and its COROLLARY 2 are used for translating from H to G1. By Kleene's THEOREM 46 (page 445)

if  |-  ph in H then  |-  ->..  ph in G1

By Kleene's COROLLARY 2 of THEOREM 46 (page 446)

if  |-  (. ph  ->.  ps ). in H then  |-  ph  ->..  ps in G1
if  |-  (. (. ph ,. ps ).  ->.  ch ). in H then  |-  ph ,. ps  ->..  ch in G1
if  |-  (. (. ph ,. ps ,. ch ).  ->.  th ). in H then  |-  ph ,. ps ,. ch  ->..  th in G1

The procedure for more direct proving of theorems or deductions in H is as follows. The User proves in G1. He(she) uses translated set.mm theorems and deductions as reference theorems and deductions. His(her) proof is only a guess in the sense that he(she) can't verify his(her) proof in G1 because he(she) doesn't have an automated proof checker to use. The proof in G1 is translated into its analog in H for verification by the Metamath program. This proof is called the Virtual Deduction proof. This proof may then be translated into a conventional Metamath proof automatically, removing the unnecessary Virtual Deduction symbols.

The translations from H to G1 and G1 to H are trivial. In practice, they may be done without much thought. In principle, they must be done, because the proving is done using sequents, which do not exist in H.

The analogs in H of the postulates of G1 are the set.mm postulates. The postulates in G1 corresponding to the Metamath postulates are not the classical system G1 postulates of Kleene (pages 442 and 443). set.mm has the predicate calculus postulates and other posulates. The Kleene classical system G1 postulates correspond to predicate calculus postulates which differ from the Metamath system G1 postulates corresponding to the predicate calculus postulates of Metamath's system H. Metamath's predicate calculus G1 postulates are presumably deducible from the Kleene classical G1 postulates and the Kleene classical G1 postulates are deducible from Metamath's G1 postulates. It should be recognized that, because of the different postulates, the classical G1 system corresponding to Metamath's system H is not identical to Kleene's classical system G1.

Why not create a separate database (setg.mm) of proofs in G1, avoiding the need to translate from H to G1 and from G1 back to H? The translations are trivial. Sequents make the language more complex than is necessary. More direct proving using sequent calculus may be done as a means towards the end of constructing proofs in H. Then, the language may be kept as simple as possible. A system G1 database would be redundant because it would duplicate the information contained in the corresponding system H database.

For earlier proofs, each "User's Proof" in the web page description of a Virtual Deduction proof in set.mm is the analog in H of the User's working proof in G1. The User's Proof is automatically completed by completeusersproof.cmd. The completed proof is the Virtual Deduction proof, which is the analog in H of the corresponding fully detailed proof in G1. The completed Virtual Deduction proof of these earlier proofs may be automatically translated into a conventional Metamath proof.

In September of 2016 completeusersproof.c was released. The input for completeusersproof.c is a Virtual Deduction User's Proof. Unlike completeusersproof.cmd, the completed proof is in conventional notation. completeusersproof.c eliminates the virtual deduction notation of the User's Proof after utilizing the information it provides.

Applying mmj2's unify command is essential to completeusersproof.c. The mmj2 program is invoked within the completeusersproof.c function mmj2Unify(). The original mmj2 program was written by Mel O'Cat. Mario Carneiro has enhanced it. mmj2Unify() is called multiple times during the execution of completeusersproof.

A Virtual Deduction proof is the Metamath-specific version of a Natural Deduction Proof. A Virtual Deduction proof generally cannot be directly input on a mmj2 Proof Worksheet and completed by the mmj2 tool because it is usually missing some technical proof steps which are not part of the Virtual Deduction proof but are necessary for a complete Metamath Proof. These missing technical steps may be automatically added by an automated proof assistant. completeusersproof.c is such a proof assistant. completeusersproof.c adds the missing technical steps and finds the reference theorems and deductions in set.mm which unify with the subproofs of the proof.

The User may write a Virtual Deduction proof and automatically transform it into a complete Metamath proof using the completeusersproof tool. The completed proof has been checked by the Metamath program. The task of writing a complete Metamath proof is reduced to writing what is essentially a Natural Deduction Proof.

Generally, proving using Virtual Deduction and completeusersproof reduces the amount Metamath-specific knowledge required by the User. Often, no knowledge of the specific theorems and deductions in set.mm is required to write some of the subproofs of a Virtual Deduction proof. Often, no knowledge of the Metamath-specific names of reference theorems and deductions in set.mm is required for writing some of the subproofs of a User's Proof. Often, the User may write subproofs of a proof using theorems or deductions commonly used in mathematics and correctly assume that some form of each is contained in set.mm and that completeusersproof will automatically generate the technical steps necessary to utilize them to complete the subproofs. Often, the fraction of the work which may be considered tedious is reduced and the total amount of work is reduced.

 wff  (.
 ph 
 ->.  ps ).
 
18.25.5  Virtual Deduction Theorems
 
Definitiondf-vd1 28637 Definition of virtual deduction. (Contributed by Alan Sare, 21-Apr-2011.) (New usage is discouraged.)
 |-  ( (. ph  ->.  ps ).  <->  ( ph  ->  ps ) )
 
Theoremin1 28638 Inference form of df-vd1 28637. Virtual deduction introduction rule of converting the virtual hypothesis of a 1-virtual hypothesis virtual deduction into an antecedent. (Contributed by Alan Sare, 14-Nov-2011.) (Proof modification is discouraged.) (New usage is discouraged.)
 |-  (. ph  ->.  ps
 ).   =>    |-  ( ph  ->  ps )
 
Theoremiin1 28639 in1 28638 without virtual deductions. (Contributed by Alan Sare, 23-Jul-2011.) (Proof modification is discouraged.) (New usage is discouraged.)
 |-  ( ph  ->  ps )   =>    |-  ( ph  ->  ps )
 
Theoremdfvd1ir 28640 Inference form of df-vd1 28637 with the virtual deduction as the assertion. (Contributed by Alan Sare, 14-Nov-2011.) (Proof modification is discouraged.) (New usage is discouraged.)
 |-  ( ph  ->  ps )   =>    |- 
 (. ph  ->.  ps ).
 
Theoremidn1 28641 Virtual deduction identity rule which is id 19 with virtual deduction symbols. (Contributed by Alan Sare, 24-Jun-2011.) (Proof modification is discouraged.) (New usage is discouraged.)
 |-  (. ph  ->.  ph ).
 
Theoremax172 28642* Quantification of two variables over a formula in which they do not occur. (Contributed by Alan Sare, 12-Apr-2011.) (Proof modification is discouraged.) (New usage is discouraged.)
 |-  ( ph  ->  A. x A. y ph )
 
Theoremdfvd1imp 28643 Left-to-right part of definition of virtual deduction. (Contributed by Alan Sare, 21-Apr-2011.) (Proof modification is discouraged.) (New usage is discouraged.)
 |-  ( (. ph  ->.  ps ).  ->  ( ph  ->  ps ) )
 
Theoremdfvd1impr 28644 Right-to-left part of definition of virtual deduction. (Contributed by Alan Sare, 21-Apr-2011.) (Proof modification is discouraged.) (New usage is discouraged.)
 |-  (
 ( ph  ->  ps )  ->  (. ph  ->.  ps ). )
 
Syntaxwvd2 28645 Syntax for a 2-hypothesis virtual deduction. (New usage is discouraged.)
 wff  (.
 ph ,. ps  ->.  ch ).
 
Definitiondf-vd2 28646 Definition of a 2-hypothesis virtual deduction. (Contributed by Alan Sare, 14-Nov-2011.) (New usage is discouraged.)
 |-  ( (. ph ,. ps  ->.  ch ).  <->  ( ( ph  /\ 
 ps )  ->  ch )
 )
 
Theoremdfvd2 28647 Definition of a 2-hypothesis virtual deduction. (Contributed by Alan Sare, 14-Nov-2011.) (Proof modification is discouraged.) (New usage is discouraged.)
 |-  ( (. ph ,. ps  ->.  ch ).  <->  ( ph  ->  ( ps  ->  ch )
 ) )
 
Syntaxwvhc2 28648 Syntax for a 2-virtual hypotheses collection. (Contributed by Alan Sare, 23-Apr-2015.) (New usage is discouraged.)
 wff  (.
 ph ,. ps ).
 
Definitiondf-vhc2 28649 Definition of a 2-virtual hypotheses collection. (Contributed by Alan Sare, 23-Apr-2015.) (New usage is discouraged.)
 |-  ( (. ph ,. ps ).  <->  (
 ph  /\  ps )
 )
 
Theoremdfvd2an 28650 Definition of a 2-hypothesis virtual deduction in vd conjunction form. (Contributed by Alan Sare, 23-Apr-2015.) (Proof modification is discouraged.) (New usage is discouraged.)
 |-  ( (. (. ph ,. ps ).  ->.  ch ).  <->  ( ( ph  /\ 
 ps )  ->  ch )
 )
 
Theoremdfvd2ani 28651 Inference form of dfvd2an 28650. (Contributed by Alan Sare, 23-Apr-2015.) (Proof modification is discouraged.) (New usage is discouraged.)
 |-  (. (. ph
 ,. ps ).  ->.  ch ).   =>    |-  ( ( ph  /\ 
 ps )  ->  ch )
 
Theoremdfvd2anir 28652 Right-to-left inference form of dfvd2an 28650. (Contributed by Alan Sare, 23-Apr-2015.) (Proof modification is discouraged.) (New usage is discouraged.)
 |-  (
 ( ph  /\  ps )  ->  ch )   =>    |- 
 (. (. ph ,. ps ).  ->.  ch ).
 
Theoremdfvd2i 28653 Inference form of dfvd2 28647. (Contributed by Alan Sare, 14-Nov-2011.) (Proof modification is discouraged.) (New usage is discouraged.)
 |-  (. ph ,. ps  ->.  ch ).   =>    |-  ( ph  ->  ( ps  ->  ch ) )
 
Theoremdfvd2ir 28654 Right-to-left inference form of dfvd2 28647. (Contributed by Alan Sare, 14-Nov-2011.) (Proof modification is discouraged.) (New usage is discouraged.)
 |-  ( ph  ->  ( ps  ->  ch ) )   =>    |- 
 (. ph ,. ps  ->.  ch ).
 
Syntaxwvd3 28655 Syntax for a 3-hypothesis virtual deduction. (New usage is discouraged.)
 wff  (.
 ph ,. ps ,. ch  ->.  th
 ).
 
Syntaxwvhc3 28656 Syntax for a 3-virtual hypotheses collection. (Contributed by Alan Sare, 13-Jun-2015.) (New usage is discouraged.)
 wff  (.
 ph ,. ps ,. ch ).
 
Definitiondf-vhc3 28657 Definition of a 3-virtual hypotheses collection. (Contributed by Alan Sare, 13-Jun-2015.) (New usage is discouraged.)
 |-  ( (. ph ,. ps ,. ch ).  <->  ( ph  /\  ps  /\ 
 ch ) )
 
Definitiondf-vd3 28658 Definition of a 3-hypothesis virtual deduction. (Contributed by Alan Sare, 14-Nov-2011.) (New usage is discouraged.)
 |-  ( (. ph ,. ps ,. ch  ->. 
 th ).  <->  ( ( ph  /\ 
 ps  /\  ch )  ->  th ) )
 
Theoremdfvd3 28659 Definition of a 3-hypothesis virtual deduction. (Contributed by Alan Sare, 14-Nov-2011.) (Proof modification is discouraged.) (New usage is discouraged.)
 |-  ( (. ph ,. ps ,. ch  ->. 
 th ).  <->  ( ph  ->  ( ps  ->  ( ch  ->  th ) ) ) )
 
Theoremdfvd3i 28660 Inference form of dfvd3 28659. (Contributed by Alan Sare, 14-Nov-2011.) (Proof modification is discouraged.) (New usage is discouraged.)
 |-  (. ph ,. ps ,. ch  ->.  th ).   =>    |-  ( ph  ->  ( ps  ->  ( ch  ->  th ) ) )
 
Theoremdfvd3ir 28661 Right-to-left inference form of dfvd3 28659. (Contributed by Alan Sare, 14-Nov-2011.) (Proof modification is discouraged.) (New usage is discouraged.)
 |-  ( ph  ->  ( ps  ->  ( ch  ->  th )
 ) )   =>    |- 
 (. ph ,. ps ,. ch  ->. 
 th ).
 
Theoremdfvd3an 28662 Definition of a 3-hypothesis virtual deduction in vd conjunction form. (Contributed by Alan Sare, 13-Jun-2015.) (Proof modification is discouraged.) (New usage is discouraged.)
 |-  ( (. (. ph ,. ps ,. ch ).  ->.  th ).  <->  ( ( ph  /\ 
 ps  /\  ch )  ->  th ) )
 
Theoremdfvd3ani 28663 Inference form of dfvd3an 28662. (Contributed by Alan Sare, 13-Jun-2015.) (Proof modification is discouraged.) (New usage is discouraged.)
 |-  (. (. ph
 ,. ps ,. ch ).  ->.  th
 ).   =>    |-  ( ( ph  /\  ps  /\ 
 ch )  ->  th )
 
Theoremdfvd3anir 28664 Right-to-left inference form of dfvd3an 28662. (Contributed by Alan Sare, 13-Jun-2015.) (Proof modification is discouraged.) (New usage is discouraged.)
 |-  (
 ( ph  /\  ps  /\  ch )  ->  th )   =>    |-  (. (. ph
 ,. ps ,. ch ).  ->.  th
 ).
 
Syntaxwvhc4 28665 Syntax for a 4-virtual hypotheses collection. (Contributed by Alan Sare, 17-Oct-2017.) (New usage is discouraged.)
 wff  (.
 ph ,. ps ,. ch ,. th ).
 
Syntaxwvhc5 28666 Syntax for a 5-virtual hypotheses collection. (Contributed by Alan Sare, 17-Oct-2017.) (New usage is discouraged.)
 wff  (.
 ph ,. ps ,. ch ,. th ,. ta ).
 
Syntaxwvhc6 28667 Syntax for a 6-element virtual hypotheses collection. (Contributed by Alan Sare, 17-Oct-2017.) (New usage is discouraged.)
 wff  (.
 ph ,. ps ,. ch ,. th ,. ta ,. et ).
 
Syntaxwvhc7 28668 Syntax for a 7-element virtual hypotheses collection. (Contributed by Alan Sare, 17-Oct-2017.) (New usage is discouraged.)
 wff  (.
 ph ,. ps ,. ch ,. th ,. ta ,. et ,. ze ).
 
Syntaxwvhc8 28669 Syntax for an 8-element virtual hypotheses collection. (Contributed by Alan Sare, 17-Oct-2017.) (New usage is discouraged.)
 wff  (.
 ph ,. ps ,. ch ,. th ,. ta ,. et ,. ze ,. si ).
 
Syntaxwvhc9 28670 Syntax for a 9-element virtual hypotheses collection. (Contributed by Alan Sare, 17-Oct-2017.) (New usage is discouraged.)
 wff  (.
 ph ,. ps ,. ch ,. th ,. ta ,. et ,. ze ,. si ,. rh ).
 
Syntaxwvhc10 28671 Syntax for a 10-element virtual hypotheses collection. (Contributed by Alan Sare, 17-Oct-2017.) (New usage is discouraged.)
 wff  (.
 ph ,. ps ,. ch ,. th ,. ta ,. et ,. ze ,. si ,. rh ,. mu ).
 
Syntaxwvhc11 28672 Syntax for an 11-element virtual hypotheses collection. (Contributed by Alan Sare, 17-Oct-2017.) (New usage is discouraged.)
 wff  (.
 ph ,. ps ,. ch ,. th ,. ta ,. et ,. ze ,. si ,. rh ,. mu ,. la
 ).
 
Syntaxwvhc12 28673 Syntax for an 12-element virtual hypotheses collection. (Contributed by Alan Sare, 17-Oct-2017.) (New usage is discouraged.)
 wff  (.
 ph ,. ps ,. ch ,. th ,. ta ,. et ,. ze ,. si ,. rh ,. mu ,. la
 ,. ka ).
 
Theoremvd01 28674 A virtual hypothesis virtually infers a theorem. (Contributed by Alan Sare, 14-Jun-2011.) (Proof modification is discouraged.) (New usage is discouraged.)
 |-  ph   =>    |- 
 (. ps  ->.  ph ).
 
Theoremvd02 28675 2 virtual hypotheses virtually infer a theorem. (Contributed by Alan Sare, 14-Jun-2011.) (Proof modification is discouraged.) (New usage is discouraged.)
 |-  ph   =>    |- 
 (. ps ,. ch  ->.  ph ).
 
Theoremvd03 28676 A theorem is virtually inferred by the 3 virtual hypotheses. (Contributed by Alan Sare, 12-Jun-2011.) (Proof modification is discouraged.) (New usage is discouraged.)
 |-  ph   =>    |- 
 (. ps ,. ch ,. th  ->. 
 ph ).
 
Theoremvd12 28677 A virtual deduction with 1 virtual hypothesis virtually inferring a virtual conclusion infers that the same conclusion is virtually inferred by the same virtual hypothesis and an additional hypothesis. (Contributed by Alan Sare, 12-Jun-2011.) (Proof modification is discouraged.) (New usage is discouraged.)
 |-  (. ph  ->.  ps
 ).   =>    |- 
 (. ph ,. ch  ->.  ps ).
 
Theoremvd13 28678 A virtual deduction with 1 virtual hypothesis virtually inferring a virtual conclusion infers that the same conclusion is virtually inferred by the same virtual hypothesis and a two additional hypotheses. (Contributed by Alan Sare, 12-Jun-2011.) (Proof modification is discouraged.) (New usage is discouraged.)
 |-  (. ph  ->.  ps
 ).   =>    |- 
 (. ph ,. ch ,. th  ->.  ps ).
 
Theoremvd23 28679 A virtual deduction with 2 virtual hypotheses virtually inferring a virtual conclusion infers that the same conclusion is virtually inferred by the same 2 virtual hypotheses and a third hypothesis. (Contributed by Alan Sare, 12-Jun-2011.) (Proof modification is discouraged.) (New usage is discouraged.)
 |-  (. ph ,. ps  ->.  ch ).   =>    |- 
 (. ph ,. ps ,. th  ->.  ch ).
 
Theoremdfvd2imp 28680 The virtual deduction form of a 2-antecedent nested implication implies the 2-antecedent nested implication. (Contributed by Alan Sare, 21-Apr-2011.) (Proof modification is discouraged.) (New usage is discouraged.)
 |-  ( (. ph ,. ps  ->.  ch ).  ->  (
 ph  ->  ( ps  ->  ch ) ) )
 
Theoremdfvd2impr 28681 A 2-antecedent nested implication implies its virtual deduction form. (Contributed by Alan Sare, 21-Apr-2011.) (Proof modification is discouraged.) (New usage is discouraged.)
 |-  (
 ( ph  ->  ( ps 
 ->  ch ) )  ->  (. ph ,. ps  ->.  ch ). )
 
Theoremin2 28682 The virtual deduction introduction rule of converting the end virtual hypothesis of 2 virtual hypotheses into an antecedent. (Contributed by Alan Sare, 21-Apr-2011.) (Proof modification is discouraged.) (New usage is discouraged.)
 |-  (. ph ,. ps  ->.  ch ).   =>    |- 
 (. ph  ->.  ( ps  ->  ch ) ).
 
Theoremint2 28683 The virtual deduction introduction rule of converting the end virtual hypothesis of 2 virtual hypotheses into an antecedent. Conventional form of int2 28683 is ex 423. (Contributed by Alan Sare, 23-Apr-2015.) (Proof modification is discouraged.) (New usage is discouraged.)
 |-  (. (. ph
 ,. ps ).  ->.  ch ).   =>    |-  (. ph  ->.  ( ps  ->  ch ) ).
 
Theoremiin2 28684 in2 28682 without virtual deductions. (Contributed by Alan Sare, 20-Jun-2011.) (Proof modification is discouraged.) (New usage is discouraged.)
 |-  ( ph  ->  ( ps  ->  ch ) )   =>    |-  ( ph  ->  ( ps  ->  ch ) )
 
Theoremin2an 28685 The virtual deduction introduction rule converting the second conjunct of the second virtual hypothesis into the antecedent of the conclusion. exp3a 425 is the non-virtual deduction form of in2an 28685. (Contributed by Alan Sare, 30-Jun-2012.) (Proof modification is discouraged.) (New usage is discouraged.)
 |-  (. ph ,. ( ps  /\  ch ) 
 ->.  th ).   =>    |- 
 (. ph ,. ps  ->.  ( ch  ->  th ) ).
 
Theoremin3 28686 The virtual deduction introduction rule of converting the end virtual hypothesis of 3 virtual hypotheses into an antecedent. (Contributed by Alan Sare, 12-Jun-2011.) (Proof modification is discouraged.) (New usage is discouraged.)
 |-  (. ph ,. ps ,. ch  ->.  th ).   =>    |-  (. ph ,. ps  ->.  ( ch  ->  th ) ).
 
Theoremiin3 28687 in3 28686 without virtual deduction connectives. Special theorem needed for Alan Sare's virtual deduction translation tool. (Contributed by Alan Sare, 23-Jul-2011.) (Proof modification is discouraged.) (New usage is discouraged.)
 |-  ( ph  ->  ( ps  ->  ( ch  ->  th )
 ) )   =>    |-  ( ph  ->  ( ps  ->  ( ch  ->  th ) ) )
 
Theoremin3an 28688 The virtual deduction introduction rule converting the second conjunct of the third virtual hypothesis into the antecedent of the conclusion. exp4a 589 is the non-virtual deduction form of in3an 28688. (Contributed by Alan Sare, 25-Jun-2012.) (Proof modification is discouraged.) (New usage is discouraged.)
 |-  (. ph ,. ps ,. ( ch 
 /\  th )  ->.  ta ).   =>    |-  (. ph ,. ps ,. ch  ->.  ( th  ->  ta ) ).
 
Theoremint3 28689 The virtual deduction introduction rule of converting the end virtual hypothesis of 3 virtual hypotheses into an antecedent. Conventional form of int3 28689 is 3expia 1153. (Contributed by Alan Sare, 13-Jun-2015.) (Proof modification is discouraged.) (New usage is discouraged.)
 |-  (. (. ph
 ,. ps ,. ch ).  ->.  th
 ).   =>    |- 
 (. (. ph ,. ps ).  ->.  ( ch  ->  th ) ).
 
Theoremidn2 28690 Virtual deduction identity rule which is idd 21 with virtual deduction symbols. (Contributed by Alan Sare, 21-Apr-2011.) (Proof modification is discouraged.) (New usage is discouraged.)
 |-  (. ph ,. ps  ->.  ps ).
 
Theoremiden2 28691 Virtual deduction identity rule. simpr 447 in conjunction form Virtual Deduction notation. (Contributed by Alan Sare, 5-Sep-2016.) (Proof modification is discouraged.) (New usage is discouraged.)
 |-  (. (. ph
 ,. ps ).  ->.  ps ).
 
Theoremidn3 28692 Virtual deduction identity rule for 3 virtual hypotheses. (Contributed by Alan Sare, 11-Jun-2011.) (Proof modification is discouraged.) (New usage is discouraged.)
 |-  (. ph ,. ps ,. ch  ->.  ch ).
 
Theoremgen11 28693* Virtual deduction generalizing rule for 1 quantifying variable and 1 virtual hypothesis. alrimiv 1621 is gen11 28693 without virtual deductions. (Contributed by Alan Sare, 21-Apr-2011.) (Proof modification is discouraged.) (New usage is discouraged.)
 |-  (. ph  ->.  ps
 ).   =>    |- 
 (. ph  ->.  A. x ps ).
 
Theoremgen11nv 28694 Virtual deduction generalizing rule for 1 quantifying variable and 1 virtual hypothesis without distinct variables. alrimih 1555 is gen11nv 28694 without virtual deductions. (Contributed by Alan Sare, 12-Dec-2011.) (Proof modification is discouraged.) (New usage is discouraged.)
 |-  ( ph  ->  A. x ph )   &    |-  (. ph  ->.  ps
 ).   =>    |- 
 (. ph  ->.  A. x ps ).
 
Theoremgen12 28695* Virtual deduction generalizing rule for 2 quantifying variables and 1 virtual hypothesis. gen12 28695 is alrimivv 1622 with virtual deductions. (Contributed by Alan Sare, 2-May-2011.) (Proof modification is discouraged.) (New usage is discouraged.)
 |-  (. ph  ->.  ps
 ).   =>    |- 
 (. ph  ->.  A. x A. y ps ).
 
Theoremgen21 28696* Virtual deduction generalizing rule for 1 quantifying variables and 2 virtual hypothesis. gen21 28696 is alrimdv 1623 with virtual deductions. (Contributed by Alan Sare, 25-Jul-2011.) (Proof modification is discouraged.) (New usage is discouraged.)
 |-  (. ph ,. ps  ->.  ch ).   =>    |- 
 (. ph ,. ps  ->.  A. x ch ).
 
Theoremgen21nv 28697 Virtual deduction form of alrimdh 1577. (Contributed by Alan Sare, 31-Dec-2011.) (Proof modification is discouraged.) (New usage is discouraged.)
 |-  ( ph  ->  A. x ph )   &    |-  ( ps  ->  A. x ps )   &    |-  (. ph ,. ps  ->.  ch ).   =>    |- 
 (. ph ,. ps  ->.  A. x ch ).
 
Theoremgen31 28698* Virtual deduction generalizing rule for 1 quantifying variable and 3 virtual hypothesis. gen31 28698 is ggen31 28609 with virtual deductions. (Contributed by Alan Sare, 22-Jun-2012.) (Proof modification is discouraged.) (New usage is discouraged.)
 |-  (. ph ,. ps ,. ch  ->.  th ).   =>    |-  (. ph ,. ps ,. ch  ->.  A. x th ).
 
Theoremgen22 28699* Virtual deduction generalizing rule for 2 quantifying variables and 2 virtual hypothesis. (Contributed by Alan Sare, 25-Jul-2011.) (Proof modification is discouraged.) (New usage is discouraged.)
 |-  (. ph ,. ps  ->.  ch ).   =>    |- 
 (. ph ,. ps  ->.  A. x A. y ch ).
 
Theoremggen22 28700* gen22 28699 without virtual deductions. (Contributed by Alan Sare, 25-Jul-2011.) (Proof modification is discouraged.) (New usage is discouraged.)
 |-  ( ph  ->  ( ps  ->  ch ) )   =>    |-  ( ph  ->  ( ps  ->  A. x A. y ch ) )
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