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| Type | Label | Description |
|---|---|---|
| Statement | ||
| Theorem | hbim1 1101 | A closed form of hbim 1005. |
| Theorem | albid 1102 | Formula-building rule for universal quantifier (deduction rule). |
| Theorem | exbid 1103 | Formula-building rule for existential quantifier (deduction rule). |
| Theorem | exan 1104 | Place a conjunct in the scope of an existential quantifier. |
| Theorem | albi 1105 | Split a biconditional and distribute quantifier. |
| Theorem | 2albi 1106 | Split a biconditional and distribute 2 quantifiers. |
| Theorem | hbnd 1107 | Deduction form of bound-variable hypothesis builder hbn 1002. |
| Theorem | hbimd 1108 | Deduction form of bound-variable hypothesis builder hbim 1005. |
| Theorem | hband 1109 | Deduction form of bound-variable hypothesis builder hban 1007. |
| Theorem | hbbid 1110 | Deduction form of bound-variable hypothesis builder hbbi 1008. |
| Theorem | hbald 1111 | Deduction form of bound-variable hypothesis builder hbal 1003. |
| Theorem | hbexd 1112 | Deduction form of bound-variable hypothesis builder hbex 1004. |
| Theorem | 19.21t 1113 | Closed form of Theorem 19.21 of [Margaris] p. 90. |
| Theorem | 19.23t 1114 | Closed form of Theorem 19.23 of [Margaris] p. 90. |
| Theorem | exintr 1115 | Introduce a conjunct in the scope of an existential quantifier. |
| Theorem | exintrbi 1116 | Add/remove a conjunct in the scope of an existential quantifier. (Contributed by Raph Levien, 3-Jul-2006.) |
| Theorem | aaan 1117 | Rearrange universal quantifiers. |
| Theorem | eeor 1118 | Rearrange existential quantifiers. |
| Theorem | qexmid 1119 | Quantified "excluded middle." Exercise 9.2a of Boolos, p. 111, Computability and Logic. |
| Equality | ||
| Theorem | ax9o 1120 |
Show that the original axiom ax-9o 1121 can be derived from ax-9 963
and
others. See ax9 1122 for the rederivation of ax-9 963
from ax-9o 1121.
This theorem should not be referenced in any proof. Instead, use ax-9o 1121 below so that uses of ax-9o 1121 can be more easily identified. |
| Axiom | ax-9o 1121 |
A variant of ax-9 963. Axiom scheme C10' in [Megill] p. 448 (p. 16 of the
preprint).
This axiom is redundant, as shown by theorem ax9o 1120. |
| Theorem | ax9 1122 |
Rederivation of axiom ax-9 963 from the orginal version, ax-9o 1121.
See ax9o 1120 for the derivation of ax-9o 1121 from ax-9 963. Lemma L18 in
[Megill] p. 446 (p. 14 of the preprint).
This theorem should not be referenced in any proof. Instead, use ax-9 963 above so that uses of ax-9 963 can be more easily identified. |
| Theorem | a9e 1123 | At least one individual exists. This is not a theorem of free logic, which is sound in empty domains. For such a logic, we would add this theorem as an axiom of set theory (Axiom 0 of [Kunen] p. 10). In the system consisting of ax-5 958 through ax-14 968 and ax-17 969, all axioms other than ax-9 963 are believed to be theorems of free logic, although the system without ax-9 963 is probably not complete in free logic. |
| Theorem | equid 1124 | Identity law for equality (reflexivity). Lemma 6 of [Tarski] p. 68. This is often an axiom of equality in textbook systems, but we don't need it as an axiom since it can be proved from our other axioms (although the proof, as you can see below, is not as obvious as you might think). This proof uses only axioms without distinct variable conditions and thus requires no dummy variables. A simpler proof, similar to Tarki's, is possible if we make use of ax-17 969; see the proof of equid1 1267. |
| Theorem | stdpc6 1125 | One of the two equality axioms of standard predicate calculus, called reflexivity of equality. (The other one is stdpc7 1178.) Axiom 6 of [Mendelson] p. 95. Mendelson doesn't say why he prepended the redundant quantifier, but it was probably to be compatible with free logic (which is valid in the empty domain). |
| Theorem | equcomi 1126 | Commutative law for equality. Lemma 7 of [Tarski] p. 69. |
| Theorem | equcom 1127 | Commutative law for equality. |
| Theorem | equcoms 1128 | An inference commuting equality in antecedent. Used to eliminate the need for a syllogism. |
| Theorem | equtr 1129 | A transitive law for equality. |
| Theorem | equtrr 1130 | A transitive law for equality. Lemma L17 in [Megill] p. 446 (p. 14 of the preprint). |
| Theorem | equtr2 1131 | A transitive law for equality. |
| Theorem | equequ1 1132 | An equivalence law for equality. |
| Theorem | equequ2 1133 | An equivalence law for equality. |
| Theorem | elequ1 1134 | An identity law for the non-logical predicate. |
| Theorem | elequ2 1135 | An identity law for the non-logical predicate. |
| Theorem | ax11i 1136 |
Inference that has ax-11 965 (without |
| Axioms ax-10 and ax-11 | ||
| Theorem | ax10o 1137 |
Show that ax-10o 1138 can be derived from ax-10 964. An open problem is
whether this theorem can be derived from ax-10 964
and the others when
ax-11 965 is replaced with ax-11o 1216. See theorem ax10 1139
for the
rederivation of ax-10 964 from ax10o 1137.
This theorem should not be referenced in any proof. Instead, use ax-10o 1138 below so that uses of ax-10o 1138 can be more easily identified. |
| Axiom | ax-10o 1138 |
Axiom ax-10o 1138 ("o" for "old") was the
original version of ax-10 964,
before it was discovered (in May 2008) that the shorter ax-10 964
could
replace it. It appears as Axiom scheme C11' in [Megill] p. 448 (p. 16
of the preprint).
This axiom is redundant, as shown by theorem ax10o 1137. |
| Theorem | ax10 1139 |
Rederivation of ax-10 964 from original version ax-10o 1138. See theorem
ax10o 1137 for the derivation of ax-10o 1138 from ax-10 964.
This theorem should not be referenced in any proof. Instead, use ax-10 964 above so that uses of ax-10 964 can be more easily identified. |
| Theorem | alequcom 1140 |
Commutation law for identical variable specifiers. The antecedent and
consequent are true when |
| Theorem | alequcoms 1141 | A commutation rule for identical variable specifiers. |
| Theorem | nalequcoms 1142 | A commutation rule for distinct variable specifiers. |
| Theorem | hbae 1143 | All variables are effectively bound in an identical variable specifier. |
| Theorem | hbaes 1144 | Rule that applies hbae 1143 to antecedent. |
| Theorem | hbnae 1145 | All variables are effectively bound in a distinct variable specifier. Lemma L19 in [Megill] p. 446 (p. 14 of the preprint). |
| Theorem | hbnaes 1146 | Rule that applies hbnae 1145 to antecedent. |
| Theorem | equs3 1147 | Lemma used in proofs of substitution properties. |
| Theorem | equs4 1148 | Lemma used in proofs of substitution properties. |
| Theorem | equsal 1149 | A useful equivalence related to substitution. |
| Theorem | equsex 1150 | A useful equivalence related to substitution. |
| Theorem | dvelimfALT 1151 | Proof of dvelimf 1248 without using ax-11 965. See dvelimALT 1351 for a proof (of the distinct variable version dvelim 1350) that doesn't require ax-10 964. |
| Theorem | dral1 1152 | Formula-building lemma for use with the Distinctor Reduction Theorem. Part of Theorem 9.4 of [Megill] p. 448 (p. 16 of preprint). |
| Theorem | dral2 1153 | Formula-building lemma for use with the Distinctor Reduction Theorem. Part of Theorem 9.4 of [Megill] p. 448 (p. 16 of preprint). |
| Theorem | drex1 1154 | Formula-building lemma for use with the Distinctor Reduction Theorem. Part of Theorem 9.4 of [Megill] p. 448 (p. 16 of preprint). |
| Theorem | drex2 1155 | Formula-building lemma for use with the Distinctor Reduction Theorem. Part of Theorem 9.4 of [Megill] p. 448 (p. 16 of preprint). |
| Theorem | a4imt 1156 | Closed theorem form of a4im 1157. |
| Theorem | ||