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Type | Label | Description |
---|---|---|
Statement | ||
Theorem | nfe1 1401 | is not free in . (Contributed by Mario Carneiro, 11-Aug-2016.) |
Theorem | 19.23ht 1402 | Closed form of Theorem 19.23 of [Margaris] p. 90. (Contributed by NM, 7-Nov-2005.) (Revised by Mario Carneiro, 1-Feb-2015.) |
Theorem | 19.23h 1403 | Theorem 19.23 of [Margaris] p. 90. (Contributed by NM, 5-Aug-1993.) (Revised by Mario Carneiro, 1-Feb-2015.) |
Theorem | alnex 1404 | Theorem 19.7 of [Margaris] p. 89. To read this intuitionistically, think of it as "if can be refuted for all , then it is not possible to find an for which holds" (and likewise for the converse). Comparing this with dfexdc 1406 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.) |
Theorem | nex 1405 | Generalization rule for negated wff. (Contributed by NM, 18-May-1994.) |
Theorem | dfexdc 1406 | Defining given decidability. It is common in classical logic to define as but in intuitionistic logic without a decidability condition, that is only an implication not an equivalence, as seen at exalim 1407. (Contributed by Jim Kingdon, 15-Mar-2018.) |
DECID | ||
Theorem | exalim 1407 | 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 1406. (Contributed by Jim Kingdon, 29-Jul-2018.) |
The equality predicate was introduced above in wceq 1259 for use by df-tru 1262. See the comments in that section. In this section, we continue with the first "real" use of it. | ||
Theorem | weq 1408 |
Extend wff definition to include atomic formulas using the equality
predicate.
(Instead of introducing weq 1408 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 1259. This lets us avoid overloading the connective, thus preventing ambiguity that would complicate certain Metamath parsers. However, logically weq 1408 is considered to be a primitive syntax, even though here it is artificially "derived" from wceq 1259. 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.) |
Syntax | wcel 1409 |
Extend wff definition to include the membership connective between
classes.
(The purpose of introducing here is to allow us to express i.e. "prove" the wel 1410 of predicate calculus in terms of the wceq 1259 of set theory, so that we don't "overload" the connective with two syntax definitions. This is done to prevent ambiguity that would complicate some Metamath parsers. The class variables and are introduced temporarily for the purpose of this definition but otherwise not used in predicate calculus.) |
Theorem | wel 1410 |
Extend wff definition to include atomic formulas with the epsilon
(membership) predicate. This is read " is an element of
," " is a member of ," " belongs to ,"
or " contains
." Note: The
phrase " includes
" means
" is a subset of
;" to use it also
for
, 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 (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 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 1410 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 1409. This lets us avoid overloading the connective, thus preventing ambiguity that would complicate certain Metamath parsers. However, logically wel 1410 is considered to be a primitive syntax, even though here it is artificially "derived" from wcel 1409. 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.) |
Axiom | ax-8 1411 |
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 1611). Axiom scheme C8'
in [Megill] p. 448 (p. 16 of the preprint).
Also appears as Axiom C7 of
[Monk2] p. 105.
Axioms ax-8 1411 through ax-16 1711 are the axioms having to do with equality, substitution, and logical properties of our binary predicate (which later in set theory will mean "is a member of"). Note that all axioms except ax-16 1711 and ax-17 1435 are still valid even when , , and 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 1711 and ax-17 1435 only. (Contributed by NM, 5-Aug-1993.) |
Axiom | ax-10 1412 |
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 1620 ("o" for "old") and was replaced with this shorter ax-10 1412 in May 2008. The old axiom is proved from this one as theorem ax10o 1619. Conversely, this axiom is proved from ax-10o 1620 as theorem ax10 1621. (Contributed by NM, 5-Aug-1993.) |
Axiom | ax-11 1413 |
Axiom of Variable Substitution. One of the 5 equality axioms of predicate
calculus. The final consequent
is a way of
expressing "
substituted for in wff
" (cf. sb6 1782).
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 1724, ax11v2 1717 and ax-11o 1720. (Contributed by NM, 5-Aug-1993.) |
Axiom | ax-i12 1414 |
Axiom of Quantifier Introduction. One of the equality and substitution
axioms of predicate calculus with equality. Informally, it says that
whenever is
distinct from and , and is
true,
then quantified with is also true. In other words,
is irrelevant to the truth of . 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 1418 for compatibility with intuitionistic logic. (Contributed by Mario Carneiro, 31-Jan-2015.) |
Axiom | ax-bndl 1415 |
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
. 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. holds
if and are the same variable,
likewise for and ,
and
holds if 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 1414 as can be seen at axi12 1423. Whether ax-bndl 1415 can be proved from the remaining axioms including ax-i12 1414 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.) |
Axiom | ax-4 1416 |
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 , it is true for any
specific (that
would typically occur as a free variable in the wff
substituted for ). (A free variable is one that does not occur in
the scope of a quantifier: and are both
free in ,
but only is free
in .) 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 1354. Conditional forms of the converse are given by ax-12 1418, ax-16 1711, and ax-17 1435. Unlike the more general textbook Axiom of Specialization, we cannot choose a variable different from 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 1674. (Contributed by NM, 5-Aug-1993.) |
Theorem | sp 1417 | Specialization. Another name for ax-4 1416. (Contributed by NM, 21-May-2008.) |
Theorem | ax-12 1418 | Rederive the original version of the axiom from ax-i12 1414. (Contributed by Mario Carneiro, 3-Feb-2015.) |
Theorem | ax12or 1419 | Another name for ax-i12 1414. (Contributed by NM, 3-Feb-2015.) |
Axiom | ax-13 1420 | 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 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.) |
Axiom | ax-14 1421 | 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 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.) |
Theorem | hbequid 1422 | Bound-variable hypothesis builder for . This theorem tells us that any variable, including , is effectively not free in , even though is technically free according to the traditional definition of free variable. (The proof uses only ax-5 1352, ax-8 1411, ax-12 1418, and ax-gen 1354. This shows that this can be proved without ax-9 1440, even though the theorem equid 1605 cannot be. A shorter proof using ax-9 1440 is obtainable from equid 1605 and hbth 1368.) (Contributed by NM, 13-Jan-2011.) (Proof shortened by Wolf Lammen, 23-Mar-2014.) |
Theorem | axi12 1423 | Proof that ax-i12 1414 follows from ax-bndl 1415. So that we can track which theorems rely on ax-bndl 1415, proofs should reference ax-i12 1414 rather than this theorem. (Contributed by Jim Kingdon, 17-Aug-2018.) (New usage is discouraged). (Proof modification is discouraged.) |
Theorem | alequcom 1424 | Commutation law for identical variable specifiers. The antecedent and consequent are true when and are substituted with the same variable. Lemma L12 in [Megill] p. 445 (p. 12 of the preprint). (Contributed by NM, 5-Aug-1993.) |
Theorem | alequcoms 1425 | A commutation rule for identical variable specifiers. (Contributed by NM, 5-Aug-1993.) |
Theorem | nalequcoms 1426 | A commutation rule for distinct variable specifiers. (Contributed by NM, 2-Jan-2002.) (Revised by Mario Carneiro, 2-Feb-2015.) |
Theorem | nfr 1427 | Consequence of the definition of not-free. (Contributed by Mario Carneiro, 26-Sep-2016.) |
Theorem | nfri 1428 | Consequence of the definition of not-free. (Contributed by Mario Carneiro, 11-Aug-2016.) |
Theorem | nfrd 1429 | Consequence of the definition of not-free in a context. (Contributed by Mario Carneiro, 11-Aug-2016.) |
Theorem | alimd 1430 | Deduction from Theorem 19.20 of [Margaris] p. 90. (Contributed by Mario Carneiro, 24-Sep-2016.) |
Theorem | alrimi 1431 | Inference from Theorem 19.21 of [Margaris] p. 90. (Contributed by Mario Carneiro, 24-Sep-2016.) |
Theorem | nfd 1432 | Deduce that is not free in in a context. (Contributed by Mario Carneiro, 24-Sep-2016.) |
Theorem | nfdh 1433 | Deduce that is not free in in a context. (Contributed by Mario Carneiro, 24-Sep-2016.) |
Theorem | nfrimi 1434 | Moving an antecedent outside . (Contributed by Jim Kingdon, 23-Mar-2018.) |
Axiom | ax-17 1435* |
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.) |
Theorem | a17d 1436* | ax-17 1435 with antecedent. (Contributed by NM, 1-Mar-2013.) |
Theorem | nfv 1437* | If is not present in , then is not free in . (Contributed by Mario Carneiro, 11-Aug-2016.) |
Theorem | nfvd 1438* | nfv 1437 with antecedent. Useful in proofs of deduction versions of bound-variable hypothesis builders such as nfimd 1493. (Contributed by Mario Carneiro, 6-Oct-2016.) |
Axiom | ax-i9 1439 | 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 1416 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 and 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 1602, which has additional remarks. (Contributed by Mario Carneiro, 31-Jan-2015.) |
Theorem | ax-9 1440 | Derive ax-9 1440 from ax-i9 1439, the modified version for intuitionistic logic. Although ax-9 1440 does hold intuistionistically, in intuitionistic logic it is weaker than ax-i9 1439. (Contributed by NM, 3-Feb-2015.) |
Theorem | equidqe 1441 | equid 1605 with some quantification and negation without using ax-4 1416 or ax-17 1435. (Contributed by NM, 13-Jan-2011.) (Proof shortened by Wolf Lammen, 27-Feb-2014.) |
Theorem | ax4sp1 1442 | A special case of ax-4 1416 without using ax-4 1416 or ax-17 1435. (Contributed by NM, 13-Jan-2011.) |
Axiom | ax-ial 1443 | is not free in . One of the axioms of predicate logic. (Contributed by Mario Carneiro, 31-Jan-2015.) |
Axiom | ax-i5r 1444 | Axiom of quantifier collection. (Contributed by Mario Carneiro, 31-Jan-2015.) |
Theorem | spi 1445 | Inference rule reversing generalization. (Contributed by NM, 5-Aug-1993.) |
Theorem | sps 1446 | Generalization of antecedent. (Contributed by NM, 5-Aug-1993.) |
Theorem | spsd 1447 | Deduction generalizing antecedent. (Contributed by NM, 17-Aug-1994.) |
Theorem | nfbidf 1448 | An equality theorem for effectively not free. (Contributed by Mario Carneiro, 4-Oct-2016.) |
Theorem | hba1 1449 | is not free in . 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.) |
Theorem | nfa1 1450 | is not free in . (Contributed by Mario Carneiro, 11-Aug-2016.) |
Theorem | a5i 1451 | Inference generalizing a consequent. (Contributed by NM, 5-Aug-1993.) |
Theorem | nfnf1 1452 | is not free in . (Contributed by Mario Carneiro, 11-Aug-2016.) |
Theorem | hbim 1453 | If is not free in and , it is not free in . (Contributed by NM, 5-Aug-1993.) (Proof shortened by O'Cat, 3-Mar-2008.) (Revised by Mario Carneiro, 2-Feb-2015.) |
Theorem | hbor 1454 | If is not free in and , it is not free in . (Contributed by NM, 5-Aug-1993.) (Revised by NM, 2-Feb-2015.) |
Theorem | hban 1455 | If is not free in and , it is not free in . (Contributed by NM, 5-Aug-1993.) (Proof shortened by Mario Carneiro, 2-Feb-2015.) |
Theorem | hbbi 1456 | If is not free in and , it is not free in . (Contributed by NM, 5-Aug-1993.) |
Theorem | hb3or 1457 | If is not free in , , and , it is not free in . (Contributed by NM, 14-Sep-2003.) |
Theorem | hb3an 1458 | If is not free in , , and , it is not free in . (Contributed by NM, 14-Sep-2003.) |
Theorem | hba2 1459 | Lemma 24 of [Monk2] p. 114. (Contributed by NM, 29-May-2008.) |
Theorem | hbia1 1460 | Lemma 23 of [Monk2] p. 114. (Contributed by NM, 29-May-2008.) |
Theorem | 19.3h 1461 | 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.) |
Theorem | 19.3 1462 | 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.) |
Theorem | 19.16 1463 | Theorem 19.16 of [Margaris] p. 90. (Contributed by NM, 12-Mar-1993.) |
Theorem | 19.17 1464 | Theorem 19.17 of [Margaris] p. 90. (Contributed by NM, 12-Mar-1993.) |
Theorem | 19.21h 1465 | Theorem 19.21 of [Margaris] p. 90. The hypothesis can be thought of as " is not free in ." New proofs should use 19.21 1491 instead. (Contributed by NM, 5-Aug-1993.) (New usage is discouraged.) |
Theorem | 19.21bi 1466 | Inference from Theorem 19.21 of [Margaris] p. 90. (Contributed by NM, 5-Aug-1993.) |
Theorem | 19.21bbi 1467 | Inference removing double quantifier. (Contributed by NM, 20-Apr-1994.) |
Theorem | 19.27h 1468 | Theorem 19.27 of [Margaris] p. 90. (Contributed by NM, 5-Aug-1993.) |
Theorem | 19.27 1469 | Theorem 19.27 of [Margaris] p. 90. (Contributed by NM, 5-Aug-1993.) |
Theorem | 19.28h 1470 | Theorem 19.28 of [Margaris] p. 90. (Contributed by NM, 5-Aug-1993.) |
Theorem | 19.28 1471 | Theorem 19.28 of [Margaris] p. 90. (Contributed by NM, 5-Aug-1993.) |
Theorem | nfan1 1472 | A closed form of nfan 1473. (Contributed by Mario Carneiro, 3-Oct-2016.) |
Theorem | nfan 1473 | If is not free in and , it is not free in . (Contributed by Mario Carneiro, 11-Aug-2016.) (Proof shortened by Wolf Lammen, 13-Jan-2018.) |
Theorem | nf3an 1474 | If is not free in , , and , it is not free in . (Contributed by Mario Carneiro, 11-Aug-2016.) |
Theorem | nford 1475 | If in a context is not free in and , it is not free in . (Contributed by Jim Kingdon, 29-Oct-2019.) |
Theorem | nfand 1476 | If in a context is not free in and , it is not free in . (Contributed by Mario Carneiro, 7-Oct-2016.) |
Theorem | nf3and 1477 | Deduction form of bound-variable hypothesis builder nf3an 1474. (Contributed by NM, 17-Feb-2013.) (Revised by Mario Carneiro, 16-Oct-2016.) |
Theorem | hbim1 1478 | A closed form of hbim 1453. (Contributed by NM, 5-Aug-1993.) |
Theorem | nfim1 1479 | A closed form of nfim 1480. (Contributed by NM, 5-Aug-1993.) (Revised by Mario Carneiro, 24-Sep-2016.) (Proof shortened by Wolf Lammen, 2-Jan-2018.) |
Theorem | nfim 1480 | If is not free in and , it is not free in . (Contributed by Mario Carneiro, 11-Aug-2016.) (Proof shortened by Wolf Lammen, 2-Jan-2018.) |
Theorem | hbimd 1481 | Deduction form of bound-variable hypothesis builder hbim 1453. (Contributed by NM, 1-Jan-2002.) (Revised by NM, 2-Feb-2015.) |
Theorem | nfor 1482 | If is not free in and , it is not free in . (Contributed by Jim Kingdon, 11-Mar-2018.) |
Theorem | hbbid 1483 | Deduction form of bound-variable hypothesis builder hbbi 1456. (Contributed by NM, 1-Jan-2002.) |
Theorem | nfal 1484 | If is not free in , it is not free in . (Contributed by Mario Carneiro, 11-Aug-2016.) |
Theorem | nfnf 1485 | If is not free in , it is not free in . (Contributed by Mario Carneiro, 11-Aug-2016.) (Proof shortened by Wolf Lammen, 30-Dec-2017.) |
Theorem | nfalt 1486 | Closed form of nfal 1484. (Contributed by Jim Kingdon, 11-May-2018.) |
Theorem | nfa2 1487 | Lemma 24 of [Monk2] p. 114. (Contributed by Mario Carneiro, 24-Sep-2016.) |
Theorem | nfia1 1488 | Lemma 23 of [Monk2] p. 114. (Contributed by Mario Carneiro, 24-Sep-2016.) |
Theorem | 19.21ht 1489 | Closed form of Theorem 19.21 of [Margaris] p. 90. (Contributed by NM, 27-May-1997.) (New usage is discouraged.) |
Theorem | 19.21t 1490 | Closed form of Theorem 19.21 of [Margaris] p. 90. (Contributed by NM, 27-May-1997.) |
Theorem | 19.21 1491 | Theorem 19.21 of [Margaris] p. 90. The hypothesis can be thought of as " is not free in ." (Contributed by NM, 5-Aug-1993.) (Revised by Mario Carneiro, 24-Sep-2016.) |
Theorem | stdpc5 1492 | An axiom scheme of standard predicate calculus that emulates Axiom 5 of [Mendelson] p. 69. The hypothesis can be thought of as emulating " is not free in ." With this definition, the meaning of "not free" is less restrictive than the usual textbook definition; for example would not (for us) be free in by nfequid 1606. This theorem scheme can be proved as a metatheorem of Mendelson's axiom system, even though it is slightly stronger than his Axiom 5. (Contributed by NM, 22-Sep-1993.) (Revised by Mario Carneiro, 12-Oct-2016.) (Proof shortened by Wolf Lammen, 1-Jan-2018.) |
Theorem | nfimd 1493 | If in a context is not free in and , it is not free in . (Contributed by Mario Carneiro, 24-Sep-2016.) (Proof shortened by Wolf Lammen, 30-Dec-2017.) |
Theorem | aaanh 1494 | Rearrange universal quantifiers. (Contributed by NM, 12-Aug-1993.) |
Theorem | aaan 1495 | Rearrange universal quantifiers. (Contributed by NM, 12-Aug-1993.) |
Theorem | nfbid 1496 | If in a context is not free in and , it is not free in . (Contributed by Mario Carneiro, 24-Sep-2016.) (Proof shortened by Wolf Lammen, 29-Dec-2017.) |
Theorem | nfbi 1497 | If is not free in and , it is not free in . (Contributed by Mario Carneiro, 11-Aug-2016.) (Proof shortened by Wolf Lammen, 2-Jan-2018.) |
Theorem | 19.8a 1498 | If a wff is true, it is true for at least one instance. Special case of Theorem 19.8 of [Margaris] p. 89. (Contributed by NM, 5-Aug-1993.) |
Theorem | 19.23bi 1499 | Inference from Theorem 19.23 of [Margaris] p. 90. (Contributed by NM, 5-Aug-1993.) |
Theorem | exlimih 1500 | Inference from Theorem 19.23 of [Margaris] p. 90. (Contributed by NM, 5-Aug-1993.) (Proof shortened by Andrew Salmon, 13-May-2011.) |
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