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Theorem List for Intuitionistic Logic Explorer - 1401-1500   *Has distinct variable group(s)
TypeLabelDescription
Statement
 
Theoremalrimih 1401 Inference from Theorem 19.21 of [Margaris] p. 90. (Contributed by NM, 5-Aug-1993.) (New usage is discouraged.)
 |-  ( ph  ->  A. x ph )   &    |-  ( ph  ->  ps )   =>    |-  ( ph  ->  A. x ps )
 
Theoremalbii 1402 Inference adding universal quantifier to both sides of an equivalence. (Contributed by NM, 7-Aug-1994.)
 |-  ( ph  <->  ps )   =>    |-  ( A. x ph  <->  A. x ps )
 
Theorem2albii 1403 Inference adding 2 universal quantifiers to both sides of an equivalence. (Contributed by NM, 9-Mar-1997.)
 |-  ( ph  <->  ps )   =>    |-  ( A. x A. y ph  <->  A. x A. y ps )
 
Theoremhbxfrbi 1404 A utility lemma to transfer a bound-variable hypothesis builder into a definition. (Contributed by Jonathan Ben-Naim, 3-Jun-2011.)
 |-  ( ph  <->  ps )   &    |-  ( ps  ->  A. x ps )   =>    |-  ( ph  ->  A. x ph )
 
Theoremnfbii 1405 Equality theorem for not-free. (Contributed by Mario Carneiro, 11-Aug-2016.)
 |-  ( ph  <->  ps )   =>    |-  ( F/ x ph  <->  F/ x ps )
 
Theoremnfxfr 1406 A utility lemma to transfer a bound-variable hypothesis builder into a definition. (Contributed by Mario Carneiro, 11-Aug-2016.)
 |-  ( ph  <->  ps )   &    |-  F/ x ps   =>    |-  F/ x ph
 
Theoremnfxfrd 1407 A utility lemma to transfer a bound-variable hypothesis builder into a definition. (Contributed by Mario Carneiro, 24-Sep-2016.)
 |-  ( ph  <->  ps )   &    |-  ( ch  ->  F/ x ps )   =>    |-  ( ch  ->  F/ x ph )
 
Theoremalcoms 1408 Swap quantifiers in an antecedent. (Contributed by NM, 11-May-1993.)
 |-  ( A. x A. y ph  ->  ps )   =>    |-  ( A. y A. x ph  ->  ps )
 
Theoremhbal 1409 If  x is not free in  ph, it is not free in  A. y ph. (Contributed by NM, 5-Aug-1993.)
 |-  ( ph  ->  A. x ph )   =>    |-  ( A. y ph  ->  A. x A. y ph )
 
Theoremalcom 1410 Theorem 19.5 of [Margaris] p. 89. (Contributed by NM, 5-Aug-1993.)
 |-  ( A. x A. y ph  <->  A. y A. x ph )
 
Theoremalrimdh 1411 Deduction from Theorem 19.21 of [Margaris] p. 90. (Contributed by NM, 10-Feb-1997.) (Proof shortened by Andrew Salmon, 13-May-2011.)
 |-  ( ph  ->  A. x ph )   &    |-  ( ps  ->  A. x ps )   &    |-  ( ph  ->  ( ps  ->  ch ) )   =>    |-  ( ph  ->  ( ps  ->  A. x ch )
 )
 
Theoremalbidh 1412 Formula-building rule for universal quantifier (deduction rule). (Contributed by NM, 5-Aug-1993.)
 |-  ( ph  ->  A. x ph )   &    |-  ( ph  ->  ( ps  <->  ch ) )   =>    |-  ( ph  ->  (
 A. x ps  <->  A. x ch )
 )
 
Theorem19.26 1413 Theorem 19.26 of [Margaris] p. 90. Also Theorem *10.22 of [WhiteheadRussell] p. 119. (Contributed by NM, 5-Aug-1993.) (Proof shortened by Wolf Lammen, 4-Jul-2014.)
 |-  ( A. x (
 ph  /\  ps )  <->  (
 A. x ph  /\  A. x ps ) )
 
Theorem19.26-2 1414 Theorem 19.26 of [Margaris] p. 90 with two quantifiers. (Contributed by NM, 3-Feb-2005.)
 |-  ( A. x A. y ( ph  /\  ps ) 
 <->  ( A. x A. y ph  /\  A. x A. y ps ) )
 
Theorem19.26-3an 1415 Theorem 19.26 of [Margaris] p. 90 with triple conjunction. (Contributed by NM, 13-Sep-2011.)
 |-  ( A. x (
 ph  /\  ps  /\  ch ) 
 <->  ( A. x ph  /\ 
 A. x ps  /\  A. x ch ) )
 
Theorem19.33 1416 Theorem 19.33 of [Margaris] p. 90. (Contributed by NM, 5-Aug-1993.)
 |-  ( ( A. x ph 
 \/  A. x ps )  ->  A. x ( ph  \/  ps ) )
 
Theoremalrot3 1417 Theorem *11.21 in [WhiteheadRussell] p. 160. (Contributed by Andrew Salmon, 24-May-2011.)
 |-  ( A. x A. y A. z ph  <->  A. y A. z A. x ph )
 
Theoremalrot4 1418 Rotate 4 universal quantifiers twice. (Contributed by NM, 2-Feb-2005.) (Proof shortened by Wolf Lammen, 28-Jun-2014.)
 |-  ( A. x A. y A. z A. w ph  <->  A. z A. w A. x A. y ph )
 
Theoremalbiim 1419 Split a biconditional and distribute quantifier. (Contributed by NM, 18-Aug-1993.)
 |-  ( A. x (
 ph 
 <->  ps )  <->  ( A. x ( ph  ->  ps )  /\  A. x ( ps 
 ->  ph ) ) )
 
Theorem2albiim 1420 Split a biconditional and distribute 2 quantifiers. (Contributed by NM, 3-Feb-2005.)
 |-  ( A. x A. y ( ph  <->  ps )  <->  ( A. x A. y ( ph  ->  ps )  /\  A. x A. y ( ps  ->  ph ) ) )
 
Theoremhband 1421 Deduction form of bound-variable hypothesis builder hban 1482. (Contributed by NM, 2-Jan-2002.)
 |-  ( ph  ->  ( ps  ->  A. x ps )
 )   &    |-  ( ph  ->  ( ch  ->  A. x ch )
 )   =>    |-  ( ph  ->  (
 ( ps  /\  ch )  ->  A. x ( ps 
 /\  ch ) ) )
 
Theoremhb3and 1422 Deduction form of bound-variable hypothesis builder hb3an 1485. (Contributed by NM, 17-Feb-2013.)
 |-  ( ph  ->  ( ps  ->  A. x ps )
 )   &    |-  ( ph  ->  ( ch  ->  A. x ch )
 )   &    |-  ( ph  ->  ( th  ->  A. x th )
 )   =>    |-  ( ph  ->  (
 ( ps  /\  ch  /\ 
 th )  ->  A. x ( ps  /\  ch  /\  th ) ) )
 
Theoremhbald 1423 Deduction form of bound-variable hypothesis builder hbal 1409. (Contributed by NM, 2-Jan-2002.)
 |-  ( ph  ->  A. y ph )   &    |-  ( ph  ->  ( ps  ->  A. x ps ) )   =>    |-  ( ph  ->  ( A. y ps  ->  A. x A. y ps ) )
 
Syntaxwex 1424 Extend wff definition to include the existential quantifier ("there exists").
 wff  E. x ph
 
Axiomax-ie1 1425  x is bound in  E. x ph. One of the axioms of predicate logic. (Contributed by Mario Carneiro, 31-Jan-2015.)
 |-  ( E. x ph  ->  A. x E. x ph )
 
Axiomax-ie2 1426 Define existential quantification.  E. x ph means "there exists at least one set  x such that  ph is true." One of the axioms of predicate logic. (Contributed by Mario Carneiro, 31-Jan-2015.)
 |-  ( A. x ( ps  ->  A. x ps )  ->  ( A. x ( ph  ->  ps )  <->  ( E. x ph  ->  ps ) ) )
 
Theoremhbe1 1427  x is not free in  E. x ph. (Contributed by NM, 5-Aug-1993.)
 |-  ( E. x ph  ->  A. x E. x ph )
 
Theoremnfe1 1428  x is not free in  E. x ph. (Contributed by Mario Carneiro, 11-Aug-2016.)
 |- 
 F/ x E. x ph
 
Theorem19.23ht 1429 Closed form of Theorem 19.23 of [Margaris] p. 90. (Contributed by NM, 7-Nov-2005.) (Revised by Mario Carneiro, 1-Feb-2015.)
 |-  ( A. x ( ps  ->  A. x ps )  ->  ( A. x ( ph  ->  ps )  <->  ( E. x ph  ->  ps ) ) )
 
Theorem19.23h 1430 Theorem 19.23 of [Margaris] p. 90. (Contributed by NM, 5-Aug-1993.) (Revised by Mario Carneiro, 1-Feb-2015.)
 |-  ( ps  ->  A. x ps )   =>    |-  ( A. x (
 ph  ->  ps )  <->  ( E. x ph 
 ->  ps ) )
 
Theoremalnex 1431 Theorem 19.7 of [Margaris] p. 89. To read this intuitionistically, think of it as "if  ph can be refuted for all 
x, then it is not possible to find an  x for which  ph holds" (and likewise for the converse). Comparing this with dfexdc 1433 illustrates that statements which look similar (to someone used to classical logic) can be different intuitionistically due to different placement of negations. (Contributed by NM, 5-Aug-1993.) (Revised by NM, 1-Feb-2015.) (Revised by Mario Carneiro, 12-May-2015.)
 |-  ( A. x  -.  ph  <->  -. 
 E. x ph )
 
Theoremnex 1432 Generalization rule for negated wff. (Contributed by NM, 18-May-1994.)
 |- 
 -.  ph   =>    |- 
 -.  E. x ph
 
Theoremdfexdc 1433 Defining  E. x ph given decidability. It is common in classical logic to define  E. x ph as  -.  A. x -.  ph but in intuitionistic logic without a decidability condition, that is only an implication not an equivalence, as seen at exalim 1434. (Contributed by Jim Kingdon, 15-Mar-2018.)
 |-  (DECID 
 E. x ph  ->  ( E. x ph  <->  -.  A. x  -.  ph ) )
 
Theoremexalim 1434 One direction of a classical definition of existential quantification. One direction of Definition of [Margaris] p. 49. For a decidable proposition, this is an equivalence, as seen as dfexdc 1433. (Contributed by Jim Kingdon, 29-Jul-2018.)
 |-  ( E. x ph  ->  -.  A. x  -.  ph )
 
1.3.2  Equality predicate (continued)

The equality predicate was introduced above in wceq 1287 for use by df-tru 1290. See the comments in that section. In this section, we continue with the first "real" use of it.

 
Theoremweq 1435 Extend wff definition to include atomic formulas using the equality predicate.

(Instead of introducing weq 1435 as an axiomatic statement, as was done in an older version of this database, we introduce it by "proving" a special case of set theory's more general wceq 1287. This lets us avoid overloading the  = connective, thus preventing ambiguity that would complicate certain Metamath parsers. However, logically weq 1435 is considered to be a primitive syntax, even though here it is artificially "derived" from wceq 1287. Note: To see the proof steps of this syntax proof, type "show proof weq /all" in the Metamath program.) (Contributed by NM, 24-Jan-2006.)

 wff  x  =  y
 
Syntaxwcel 1436 Extend wff definition to include the membership connective between classes.

(The purpose of introducing 
wff  A  e.  B here is to allow us to express i.e. "prove" the wel 1437 of predicate calculus in terms of the wceq 1287 of set theory, so that we don't "overload" the  e. connective with two syntax definitions. This is done to prevent ambiguity that would complicate some Metamath parsers. The class variables  A and  B are introduced temporarily for the purpose of this definition but otherwise not used in predicate calculus.)

 wff  A  e.  B
 
Theoremwel 1437 Extend wff definition to include atomic formulas with the epsilon (membership) predicate. This is read " x is an element of  y," " x is a member of  y," " x belongs to  y," or " y contains  x." Note: The phrase " y includes  x " means " x is a subset of  y;" to use it also for  x  e.  y, as some authors occasionally do, is poor form and causes confusion, according to George Boolos (1992 lecture at MIT).

This syntactical construction introduces a binary non-logical predicate symbol  e. (epsilon) into our predicate calculus. We will eventually use it for the membership predicate of set theory, but that is irrelevant at this point: the predicate calculus axioms for  e. apply to any arbitrary binary predicate symbol. "Non-logical" means that the predicate is presumed to have additional properties beyond the realm of predicate calculus, although these additional properties are not specified by predicate calculus itself but rather by the axioms of a theory (in our case set theory) added to predicate calculus. "Binary" means that the predicate has two arguments.

(Instead of introducing wel 1437 as an axiomatic statement, as was done in an older version of this database, we introduce it by "proving" a special case of set theory's more general wcel 1436. This lets us avoid overloading the  e. connective, thus preventing ambiguity that would complicate certain Metamath parsers. However, logically wel 1437 is considered to be a primitive syntax, even though here it is artificially "derived" from wcel 1436. Note: To see the proof steps of this syntax proof, type "show proof wel /all" in the Metamath program.) (Contributed by NM, 24-Jan-2006.)

 wff  x  e.  y
 
Axiomax-8 1438 Axiom of Equality. One of the equality and substitution axioms of predicate calculus with equality. This is similar to, but not quite, a transitive law for equality (proved later as equtr 1639). Axiom scheme C8' in [Megill] p. 448 (p. 16 of the preprint). Also appears as Axiom C7 of [Monk2] p. 105.

Axioms ax-8 1438 through ax-16 1739 are the axioms having to do with equality, substitution, and logical properties of our binary predicate  e. (which later in set theory will mean "is a member of"). Note that all axioms except ax-16 1739 and ax-17 1462 are still valid even when  x,  y, and  z are replaced with the same variable because they do not have any distinct variable (Metamath's $d) restrictions. Distinct variable restrictions are required for ax-16 1739 and ax-17 1462 only. (Contributed by NM, 5-Aug-1993.)

 |-  ( x  =  y 
 ->  ( x  =  z 
 ->  y  =  z
 ) )
 
Axiomax-10 1439 Axiom of Quantifier Substitution. One of the equality and substitution axioms of predicate calculus with equality. Appears as Lemma L12 in [Megill] p. 445 (p. 12 of the preprint).

The original version of this axiom was ax-10o 1648 ("o" for "old") and was replaced with this shorter ax-10 1439 in May 2008. The old axiom is proved from this one as theorem ax10o 1647. Conversely, this axiom is proved from ax-10o 1648 as theorem ax10 1649. (Contributed by NM, 5-Aug-1993.)

 |-  ( A. x  x  =  y  ->  A. y  y  =  x )
 
Axiomax-11 1440 Axiom of Variable Substitution. One of the 5 equality axioms of predicate calculus. The final consequent  A. x ( x  =  y  ->  ph ) is a way of expressing " y substituted for  x in wff  ph " (cf. sb6 1811). It is based on Lemma 16 of [Tarski] p. 70 and Axiom C8 of [Monk2] p. 105, from which it can be proved by cases.

Variants of this axiom which are equivalent in classical logic but which have not been shown to be equivalent for intuitionistic logic are ax11v 1752, ax11v2 1745 and ax-11o 1748. (Contributed by NM, 5-Aug-1993.)

 |-  ( x  =  y 
 ->  ( A. y ph  ->  A. x ( x  =  y  ->  ph )
 ) )
 
Axiomax-i12 1441 Axiom of Quantifier Introduction. One of the equality and substitution axioms of predicate calculus with equality. Informally, it says that whenever  z is distinct from  x and  y, and  x  =  y is true, then  x  =  y quantified with  z is also true. In other words,  z is irrelevant to the truth of 
x  =  y. Axiom scheme C9' in [Megill] p. 448 (p. 16 of the preprint). It apparently does not otherwise appear in the literature but is easily proved from textbook predicate calculus by cases.

This axiom has been modified from the original ax-12 1445 for compatibility with intuitionistic logic. (Contributed by Mario Carneiro, 31-Jan-2015.)

 |-  ( A. z  z  =  x  \/  ( A. z  z  =  y  \/  A. z ( x  =  y  ->  A. z  x  =  y ) ) )
 
Axiomax-bndl 1442 Axiom of bundling. The general idea of this axiom is that two variables are either distinct or non-distinct. That idea could be expressed as  A. z z  =  x  \/  -.  A. z z  =  x. However, we instead choose an axiom which has many of the same consequences, but which is different with respect to a universe which contains only one object.  A. z
z  =  x holds if  z and  x are the same variable, likewise for  z and  y, and  A. x A. z ( x  =  y  ->  A. z
x  =  y ) holds if  z is distinct from the others (and the universe has at least two objects).

As with other statements of the form "x is decidable (either true or false)", this does not entail the full Law of the Excluded Middle (which is the proposition that all statements are decidable), but instead merely the assertion that particular kinds of statements are decidable (or in this case, an assertion similar to decidability).

This axiom implies ax-i12 1441 as can be seen at axi12 1450. Whether ax-bndl 1442 can be proved from the remaining axioms including ax-i12 1441 is not known.

The reason we call this "bundling" is that a statement without a distinct variable constraint "bundles" together two statements, one in which the two variables are the same and one in which they are different. (Contributed by Mario Carneiro and Jim Kingdon, 14-Mar-2018.)

 |-  ( A. z  z  =  x  \/  ( A. z  z  =  y  \/  A. x A. z ( x  =  y  ->  A. z  x  =  y ) ) )
 
Axiomax-4 1443 Axiom of Specialization. A quantified wff implies the wff without a quantifier (i.e. an instance, or special case, of the generalized wff). In other words if something is true for all  x, it is true for any specific  x (that would typically occur as a free variable in the wff substituted for  ph). (A free variable is one that does not occur in the scope of a quantifier:  x and  y are both free in  x  =  y, but only  x is free in  A. y x  =  y.) Axiom scheme C5' in [Megill] p. 448 (p. 16 of the preprint). Also appears as Axiom B5 of [Tarski] p. 67 (under his system S2, defined in the last paragraph on p. 77).

Note that the converse of this axiom does not hold in general, but a weaker inference form of the converse holds and is expressed as rule ax-gen 1381. Conditional forms of the converse are given by ax-12 1445, ax-16 1739, and ax-17 1462.

Unlike the more general textbook Axiom of Specialization, we cannot choose a variable different from  x for the special case. For use, that requires the assistance of equality axioms, and we deal with it later after we introduce the definition of proper substitution - see stdpc4 1702.

(Contributed by NM, 5-Aug-1993.)

 |-  ( A. x ph  -> 
 ph )
 
Theoremsp 1444 Specialization. Another name for ax-4 1443. (Contributed by NM, 21-May-2008.)
 |-  ( A. x ph  -> 
 ph )
 
Theoremax-12 1445 Rederive the original version of the axiom from ax-i12 1441. (Contributed by Mario Carneiro, 3-Feb-2015.)
 |-  ( -.  A. z  z  =  x  ->  ( -.  A. z  z  =  y  ->  ( x  =  y  ->  A. z  x  =  y ) ) )
 
Theoremax12or 1446 Another name for ax-i12 1441. (Contributed by NM, 3-Feb-2015.)
 |-  ( A. z  z  =  x  \/  ( A. z  z  =  y  \/  A. z ( x  =  y  ->  A. z  x  =  y ) ) )
 
Axiomax-13 1447 Axiom of Equality. One of the equality and substitution axioms for a non-logical predicate in our predicate calculus with equality. It substitutes equal variables into the left-hand side of the  e. binary predicate. Axiom scheme C12' in [Megill] p. 448 (p. 16 of the preprint). It is a special case of Axiom B8 (p. 75) of system S2 of [Tarski] p. 77. "Non-logical" means that the predicate is not a primitive of predicate calculus proper but instead is an extension to it. "Binary" means that the predicate has two arguments. In a system of predicate calculus with equality, like ours, equality is not usually considered to be a non-logical predicate. In systems of predicate calculus without equality, it typically would be. (Contributed by NM, 5-Aug-1993.)
 |-  ( x  =  y 
 ->  ( x  e.  z  ->  y  e.  z ) )
 
Axiomax-14 1448 Axiom of Equality. One of the equality and substitution axioms for a non-logical predicate in our predicate calculus with equality. It substitutes equal variables into the right-hand side of the  e. binary predicate. Axiom scheme C13' in [Megill] p. 448 (p. 16 of the preprint). It is a special case of Axiom B8 (p. 75) of system S2 of [Tarski] p. 77. (Contributed by NM, 5-Aug-1993.)
 |-  ( x  =  y 
 ->  ( z  e.  x  ->  z  e.  y ) )
 
Theoremhbequid 1449 Bound-variable hypothesis builder for  x  =  x. This theorem tells us that any variable, including  x, is effectively not free in  x  =  x, even though  x is technically free according to the traditional definition of free variable. (The proof uses only ax-5 1379, ax-8 1438, ax-12 1445, and ax-gen 1381. This shows that this can be proved without ax-9 1467, even though the theorem equid 1632 cannot be. A shorter proof using ax-9 1467 is obtainable from equid 1632 and hbth 1395.) (Contributed by NM, 13-Jan-2011.) (Proof shortened by Wolf Lammen, 23-Mar-2014.)
 |-  ( x  =  x 
 ->  A. y  x  =  x )
 
Theoremaxi12 1450 Proof that ax-i12 1441 follows from ax-bndl 1442. So that we can track which theorems rely on ax-bndl 1442, proofs should reference ax-i12 1441 rather than this theorem. (Contributed by Jim Kingdon, 17-Aug-2018.) (New usage is discouraged). (Proof modification is discouraged.)
 |-  ( A. z  z  =  x  \/  ( A. z  z  =  y  \/  A. z ( x  =  y  ->  A. z  x  =  y ) ) )
 
Theoremalequcom 1451 Commutation law for identical variable specifiers. The antecedent and consequent are true when  x and  y are substituted with the same variable. Lemma L12 in [Megill] p. 445 (p. 12 of the preprint). (Contributed by NM, 5-Aug-1993.)
 |-  ( A. x  x  =  y  ->  A. y  y  =  x )
 
Theoremalequcoms 1452 A commutation rule for identical variable specifiers. (Contributed by NM, 5-Aug-1993.)
 |-  ( A. x  x  =  y  ->  ph )   =>    |-  ( A. y  y  =  x  ->  ph )
 
Theoremnalequcoms 1453 A commutation rule for distinct variable specifiers. (Contributed by NM, 2-Jan-2002.) (Revised by Mario Carneiro, 2-Feb-2015.)
 |-  ( -.  A. x  x  =  y  ->  ph )   =>    |-  ( -.  A. y  y  =  x  ->  ph )
 
Theoremnfr 1454 Consequence of the definition of not-free. (Contributed by Mario Carneiro, 26-Sep-2016.)
 |-  ( F/ x ph  ->  ( ph  ->  A. x ph ) )
 
Theoremnfri 1455 Consequence of the definition of not-free. (Contributed by Mario Carneiro, 11-Aug-2016.)
 |- 
 F/ x ph   =>    |-  ( ph  ->  A. x ph )
 
Theoremnfrd 1456 Consequence of the definition of not-free in a context. (Contributed by Mario Carneiro, 11-Aug-2016.)
 |-  ( ph  ->  F/ x ps )   =>    |-  ( ph  ->  ( ps  ->  A. x ps )
 )
 
Theoremalimd 1457 Deduction from Theorem 19.20 of [Margaris] p. 90. (Contributed by Mario Carneiro, 24-Sep-2016.)
 |- 
 F/ x ph   &    |-  ( ph  ->  ( ps  ->  ch )
 )   =>    |-  ( ph  ->  ( A. x ps  ->  A. x ch ) )
 
Theoremalrimi 1458 Inference from Theorem 19.21 of [Margaris] p. 90. (Contributed by Mario Carneiro, 24-Sep-2016.)
 |- 
 F/ x ph   &    |-  ( ph  ->  ps )   =>    |-  ( ph  ->  A. x ps )
 
Theoremnfd 1459 Deduce that  x is not free in  ps in a context. (Contributed by Mario Carneiro, 24-Sep-2016.)
 |- 
 F/ x ph   &    |-  ( ph  ->  ( ps  ->  A. x ps ) )   =>    |-  ( ph  ->  F/ x ps )
 
Theoremnfdh 1460 Deduce that  x is not free in  ps in a context. (Contributed by Mario Carneiro, 24-Sep-2016.)
 |-  ( ph  ->  A. x ph )   &    |-  ( ph  ->  ( ps  ->  A. x ps ) )   =>    |-  ( ph  ->  F/ x ps )
 
Theoremnfrimi 1461 Moving an antecedent outside  F/. (Contributed by Jim Kingdon, 23-Mar-2018.)
 |- 
 F/ x ph   &    |-  F/ x (
 ph  ->  ps )   =>    |-  ( ph  ->  F/ x ps )
 
1.3.3  Axiom ax-17 - first use of the $d distinct variable statement
 
Axiomax-17 1462* Axiom to quantify a variable over a formula in which it does not occur. Axiom C5 in [Megill] p. 444 (p. 11 of the preprint). Also appears as Axiom B6 (p. 75) of system S2 of [Tarski] p. 77 and Axiom C5-1 of [Monk2] p. 113.

(Contributed by NM, 5-Aug-1993.)

 |-  ( ph  ->  A. x ph )
 
Theorema17d 1463* ax-17 1462 with antecedent. (Contributed by NM, 1-Mar-2013.)
 |-  ( ph  ->  ( ps  ->  A. x ps )
 )
 
Theoremnfv 1464* If  x is not present in  ph, then  x is not free in  ph. (Contributed by Mario Carneiro, 11-Aug-2016.)
 |- 
 F/ x ph
 
Theoremnfvd 1465* nfv 1464 with antecedent. Useful in proofs of deduction versions of bound-variable hypothesis builders such as nfimd 1520. (Contributed by Mario Carneiro, 6-Oct-2016.)
 |-  ( ph  ->  F/ x ps )
 
1.3.4  Introduce Axiom of Existence
 
Axiomax-i9 1466 Axiom of Existence. One of the equality and substitution axioms of predicate calculus with equality. One thing this axiom tells us is that at least one thing exists (although ax-4 1443 and possibly others also tell us that, i.e. they are not valid in the empty domain of a "free logic"). In this form (not requiring that  x and  y be distinct) it was used in an axiom system of Tarski (see Axiom B7' in footnote 1 of [KalishMontague] p. 81.) Another name for this theorem is a9e 1629, which has additional remarks. (Contributed by Mario Carneiro, 31-Jan-2015.)
 |- 
 E. x  x  =  y
 
Theoremax-9 1467 Derive ax-9 1467 from ax-i9 1466, the modified version for intuitionistic logic. Although ax-9 1467 does hold intuistionistically, in intuitionistic logic it is weaker than ax-i9 1466. (Contributed by NM, 3-Feb-2015.)
 |- 
 -.  A. x  -.  x  =  y
 
Theoremequidqe 1468 equid 1632 with some quantification and negation without using ax-4 1443 or ax-17 1462. (Contributed by NM, 13-Jan-2011.) (Proof shortened by Wolf Lammen, 27-Feb-2014.)
 |- 
 -.  A. y  -.  x  =  x
 
Theoremax4sp1 1469 A special case of ax-4 1443 without using ax-4 1443 or ax-17 1462. (Contributed by NM, 13-Jan-2011.)
 |-  ( A. y  -.  x  =  x  ->  -.  x  =  x )
 
1.3.5  Additional intuitionistic axioms
 
Axiomax-ial 1470  x is not free in  A. x ph. One of the axioms of predicate logic. (Contributed by Mario Carneiro, 31-Jan-2015.)
 |-  ( A. x ph  ->  A. x A. x ph )
 
Axiomax-i5r 1471 Axiom of quantifier collection. (Contributed by Mario Carneiro, 31-Jan-2015.)
 |-  ( ( A. x ph 
 ->  A. x ps )  ->  A. x ( A. x ph  ->  ps )
 )
 
1.3.6  Predicate calculus including ax-4, without distinct variables
 
Theoremspi 1472 Inference rule reversing generalization. (Contributed by NM, 5-Aug-1993.)
 |- 
 A. x ph   =>    |-  ph
 
Theoremsps 1473 Generalization of antecedent. (Contributed by NM, 5-Aug-1993.)
 |-  ( ph  ->  ps )   =>    |-  ( A. x ph  ->  ps )
 
Theoremspsd 1474 Deduction generalizing antecedent. (Contributed by NM, 17-Aug-1994.)
 |-  ( ph  ->  ( ps  ->  ch ) )   =>    |-  ( ph  ->  (
 A. x ps  ->  ch ) )
 
Theoremnfbidf 1475 An equality theorem for effectively not free. (Contributed by Mario Carneiro, 4-Oct-2016.)
 |- 
 F/ x ph   &    |-  ( ph  ->  ( ps  <->  ch ) )   =>    |-  ( ph  ->  ( F/ x ps  <->  F/ x ch )
 )
 
Theoremhba1 1476  x is not free in  A. x ph. Example in Appendix in [Megill] p. 450 (p. 19 of the preprint). Also Lemma 22 of [Monk2] p. 114. (Contributed by NM, 5-Aug-1993.)
 |-  ( A. x ph  ->  A. x A. x ph )
 
Theoremnfa1 1477  x is not free in  A. x ph. (Contributed by Mario Carneiro, 11-Aug-2016.)
 |- 
 F/ x A. x ph
 
Theorema5i 1478 Inference generalizing a consequent. (Contributed by NM, 5-Aug-1993.)
 |-  ( A. x ph  ->  ps )   =>    |-  ( A. x ph  ->  A. x ps )
 
Theoremnfnf1 1479  x is not free in  F/ x ph. (Contributed by Mario Carneiro, 11-Aug-2016.)
 |- 
 F/ x F/ x ph
 
Theoremhbim 1480 If  x is not free in  ph and  ps, it is not free in  ( ph  ->  ps ). (Contributed by NM, 5-Aug-1993.) (Proof shortened by O'Cat, 3-Mar-2008.) (Revised by Mario Carneiro, 2-Feb-2015.)
 |-  ( ph  ->  A. x ph )   &    |-  ( ps  ->  A. x ps )   =>    |-  ( ( ph  ->  ps )  ->  A. x ( ph  ->  ps )
 )
 
Theoremhbor 1481 If  x is not free in  ph and  ps, it is not free in  ( ph  \/  ps ). (Contributed by NM, 5-Aug-1993.) (Revised by NM, 2-Feb-2015.)
 |-  ( ph  ->  A. x ph )   &    |-  ( ps  ->  A. x ps )   =>    |-  ( ( ph  \/  ps )  ->  A. x ( ph  \/  ps )
 )
 
Theoremhban 1482 If  x is not free in  ph and  ps, it is not free in  ( ph  /\  ps ). (Contributed by NM, 5-Aug-1993.) (Proof shortened by Mario Carneiro, 2-Feb-2015.)
 |-  ( ph  ->  A. x ph )   &    |-  ( ps  ->  A. x ps )   =>    |-  ( ( ph  /\ 
 ps )  ->  A. x ( ph  /\  ps )
 )
 
Theoremhbbi 1483 If  x is not free in  ph and  ps, it is not free in  ( ph  <->  ps ). (Contributed by NM, 5-Aug-1993.)
 |-  ( ph  ->  A. x ph )   &    |-  ( ps  ->  A. x ps )   =>    |-  ( ( ph  <->  ps )  ->  A. x ( ph  <->  ps ) )
 
Theoremhb3or 1484 If  x is not free in  ph,  ps, and  ch, it is not free in  ( ph  \/  ps  \/  ch ). (Contributed by NM, 14-Sep-2003.)
 |-  ( ph  ->  A. x ph )   &    |-  ( ps  ->  A. x ps )   &    |-  ( ch  ->  A. x ch )   =>    |-  (
 ( ph  \/  ps  \/  ch )  ->  A. x (
 ph  \/  ps  \/  ch ) )
 
Theoremhb3an 1485 If  x is not free in  ph,  ps, and  ch, it is not free in  ( ph  /\  ps  /\  ch ). (Contributed by NM, 14-Sep-2003.)
 |-  ( ph  ->  A. x ph )   &    |-  ( ps  ->  A. x ps )   &    |-  ( ch  ->  A. x ch )   =>    |-  (
 ( ph  /\  ps  /\  ch )  ->  A. x (
 ph  /\  ps  /\  ch ) )
 
Theoremhba2 1486 Lemma 24 of [Monk2] p. 114. (Contributed by NM, 29-May-2008.)
 |-  ( A. y A. x ph  ->  A. x A. y A. x ph )
 
Theoremhbia1 1487 Lemma 23 of [Monk2] p. 114. (Contributed by NM, 29-May-2008.)
 |-  ( ( A. x ph 
 ->  A. x ps )  ->  A. x ( A. x ph  ->  A. x ps ) )
 
Theorem19.3h 1488 A wff may be quantified with a variable not free in it. Theorem 19.3 of [Margaris] p. 89. (Contributed by NM, 5-Aug-1993.) (Revised by NM, 21-May-2007.)
 |-  ( ph  ->  A. x ph )   =>    |-  ( A. x ph  <->  ph )
 
Theorem19.3 1489 A wff may be quantified with a variable not free in it. Theorem 19.3 of [Margaris] p. 89. (Contributed by NM, 5-Aug-1993.) (Revised by Mario Carneiro, 24-Sep-2016.)
 |- 
 F/ x ph   =>    |-  ( A. x ph  <->  ph )
 
Theorem19.16 1490 Theorem 19.16 of [Margaris] p. 90. (Contributed by NM, 12-Mar-1993.)
 |- 
 F/ x ph   =>    |-  ( A. x (
 ph 
 <->  ps )  ->  ( ph 
 <-> 
 A. x ps )
 )
 
Theorem19.17 1491 Theorem 19.17 of [Margaris] p. 90. (Contributed by NM, 12-Mar-1993.)
 |- 
 F/ x ps   =>    |-  ( A. x ( ph  <->  ps )  ->  ( A. x ph  <->  ps ) )
 
Theorem19.21h 1492 Theorem 19.21 of [Margaris] p. 90. The hypothesis can be thought of as " x is not free in  ph." New proofs should use 19.21 1518 instead. (Contributed by NM, 5-Aug-1993.) (New usage is discouraged.)
 |-  ( ph  ->  A. x ph )   =>    |-  ( A. x (
 ph  ->  ps )  <->  ( ph  ->  A. x ps ) )
 
Theorem19.21bi 1493 Inference from Theorem 19.21 of [Margaris] p. 90. (Contributed by NM, 5-Aug-1993.)
 |-  ( ph  ->  A. x ps )   =>    |-  ( ph  ->  ps )
 
Theorem19.21bbi 1494 Inference removing double quantifier. (Contributed by NM, 20-Apr-1994.)
 |-  ( ph  ->  A. x A. y ps )   =>    |-  ( ph  ->  ps )
 
Theorem19.27h 1495 Theorem 19.27 of [Margaris] p. 90. (Contributed by NM, 5-Aug-1993.)
 |-  ( ps  ->  A. x ps )   =>    |-  ( A. x (
 ph  /\  ps )  <->  (
 A. x ph  /\  ps ) )
 
Theorem19.27 1496 Theorem 19.27 of [Margaris] p. 90. (Contributed by NM, 5-Aug-1993.)
 |- 
 F/ x ps   =>    |-  ( A. x ( ph  /\  ps )  <->  (
 A. x ph  /\  ps ) )
 
Theorem19.28h 1497 Theorem 19.28 of [Margaris] p. 90. (Contributed by NM, 5-Aug-1993.)
 |-  ( ph  ->  A. x ph )   =>    |-  ( A. x (
 ph  /\  ps )  <->  (
 ph  /\  A. x ps ) )
 
Theorem19.28 1498 Theorem 19.28 of [Margaris] p. 90. (Contributed by NM, 5-Aug-1993.)
 |- 
 F/ x ph   =>    |-  ( A. x (
 ph  /\  ps )  <->  (
 ph  /\  A. x ps ) )
 
Theoremnfan1 1499 A closed form of nfan 1500. (Contributed by Mario Carneiro, 3-Oct-2016.)
 |- 
 F/ x ph   &    |-  ( ph  ->  F/ x ps )   =>    |-  F/ x (
 ph  /\  ps )
 
Theoremnfan 1500 If  x is not free in  ph and  ps, it is not free in  ( ph  /\  ps ). (Contributed by Mario Carneiro, 11-Aug-2016.) (Proof shortened by Wolf Lammen, 13-Jan-2018.)
 |- 
 F/ x ph   &    |-  F/ x ps   =>    |-  F/ x ( ph  /\  ps )
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