 Home Intuitionistic Logic ExplorerTheorem List (p. 17 of 95) < Previous  Next > Bad symbols? Try the GIF version. Mirrors  >  Metamath Home Page  >  ILE Home Page  >  Theorem List Contents  >  Recent Proofs       This page: Page List

Theorem List for Intuitionistic Logic Explorer - 1601-1700   *Has distinct variable group(s)
TypeLabelDescription
Statement

Axiomax-10o 1601 Axiom ax-10o 1601 ("o" for "old") was the original version of ax-10 1393, before it was discovered (in May 2008) that the shorter ax-10 1393 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 1600.

Normally, ax10o 1600 should be used rather than ax-10o 1601, except by theorems specifically studying the latter's properties. (Contributed by NM, 5-Aug-1993.) (New usage is discouraged.)

(x x = y → (xφyφ))

Theoremax10 1602 Rederivation of ax-10 1393 from original version ax-10o 1601. See theorem ax10o 1600 for the derivation of ax-10o 1601 from ax-10 1393.

This theorem should not be referenced in any proof. Instead, use ax-10 1393 above so that uses of ax-10 1393 can be more easily identified. (Contributed by NM, 16-May-2008.) (New usage is discouraged.)

(x x = yy y = x)

Theoremhbae 1603 All variables are effectively bound in an identical variable specifier. (Contributed by NM, 5-Aug-1993.) (Revised by NM, 3-Feb-2015.)
(x x = yzx x = y)

Theoremnfae 1604 All variables are effectively bound in an identical variable specifier. (Contributed by Mario Carneiro, 11-Aug-2016.)
zx x = y

Theoremhbaes 1605 Rule that applies hbae 1603 to antecedent. (Contributed by NM, 5-Aug-1993.)
(zx x = yφ)       (x x = yφ)

Theoremhbnae 1606 All variables are effectively bound in a distinct variable specifier. Lemma L19 in [Megill] p. 446 (p. 14 of the preprint). (Contributed by NM, 5-Aug-1993.)
x x = yz ¬ x x = y)

Theoremnfnae 1607 All variables are effectively bound in a distinct variable specifier. (Contributed by Mario Carneiro, 11-Aug-2016.)
z ¬ x x = y

Theoremhbnaes 1608 Rule that applies hbnae 1606 to antecedent. (Contributed by NM, 5-Aug-1993.)
(z ¬ x x = yφ)       x x = yφ)

Theoremnaecoms 1609 A commutation rule for distinct variable specifiers. (Contributed by NM, 2-Jan-2002.)
x x = yφ)       y y = xφ)

Theoremequs4 1610 Lemma used in proofs of substitution properties. (Contributed by NM, 5-Aug-1993.) (Proof shortened by Mario Carneiro, 20-May-2014.)
(x(x = yφ) → x(x = y φ))

Theoremequsalh 1611 A useful equivalence related to substitution. New proofs should use equsal 1612 instead. (Contributed by NM, 5-Aug-1993.) (Proof shortened by Andrew Salmon, 12-Aug-2011.) (New usage is discouraged.)
(ψxψ)    &   (x = y → (φψ))       (x(x = yφ) ↔ ψ)

Theoremequsal 1612 A useful equivalence related to substitution. (Contributed by NM, 5-Aug-1993.) (Proof shortened by Andrew Salmon, 12-Aug-2011.) (Revised by Mario Carneiro, 3-Oct-2016.) (Proof shortened by Wolf Lammen, 5-Feb-2018.)
xψ    &   (x = y → (φψ))       (x(x = yφ) ↔ ψ)

Theoremequsex 1613 A useful equivalence related to substitution. (Contributed by NM, 5-Aug-1993.) (Revised by NM, 3-Feb-2015.)
(ψxψ)    &   (x = y → (φψ))       (x(x = y φ) ↔ ψ)

Theoremequsexd 1614 Deduction form of equsex 1613. (Contributed by Jim Kingdon, 29-Dec-2017.)
(φxφ)    &   (φ → (χxχ))    &   (φ → (x = y → (ψχ)))       (φ → (x(x = y ψ) ↔ χ))

Theoremdral1 1615 Formula-building lemma for use with the Distinctor Reduction Theorem. Part of Theorem 9.4 of [Megill] p. 448 (p. 16 of preprint). (Contributed by NM, 24-Nov-1994.)
(x x = y → (φψ))       (x x = y → (xφyψ))

Theoremdral2 1616 Formula-building lemma for use with the Distinctor Reduction Theorem. Part of Theorem 9.4 of [Megill] p. 448 (p. 16 of preprint). (Contributed by NM, 27-Feb-2005.)
(x x = y → (φψ))       (x x = y → (zφzψ))

Theoremdrex2 1617 Formula-building lemma for use with the Distinctor Reduction Theorem. Part of Theorem 9.4 of [Megill] p. 448 (p. 16 of preprint). (Contributed by NM, 27-Feb-2005.)
(x x = y → (φψ))       (x x = y → (zφzψ))

Theoremdrnf1 1618 Formula-building lemma for use with the Distinctor Reduction Theorem. (Contributed by Mario Carneiro, 4-Oct-2016.)
(x x = y → (φψ))       (x x = y → (Ⅎxφ ↔ Ⅎyψ))

Theoremdrnf2 1619 Formula-building lemma for use with the Distinctor Reduction Theorem. (Contributed by Mario Carneiro, 4-Oct-2016.)
(x x = y → (φψ))       (x x = y → (Ⅎzφ ↔ Ⅎzψ))

Theoremspimth 1620 Closed theorem form of spim 1623. (Contributed by NM, 15-Jan-2008.) (New usage is discouraged.)
(x((ψxψ) (x = y → (φψ))) → (xφψ))

Theoremspimt 1621 Closed theorem form of spim 1623. (Contributed by NM, 15-Jan-2008.) (Revised by Mario Carneiro, 17-Oct-2016.) (Proof shortened by Wolf Lammen, 24-Feb-2018.)
((Ⅎxψ x(x = y → (φψ))) → (xφψ))

Theoremspimh 1622 Specialization, using implicit substitition. Compare Lemma 14 of [Tarski] p. 70. The spim 1623 series of theorems requires that only one direction of the substitution hypothesis hold. (Contributed by NM, 5-Aug-1993.) (Revised by NM, 8-May-2008.) (New usage is discouraged.)
(ψxψ)    &   (x = y → (φψ))       (xφψ)

Theoremspim 1623 Specialization, using implicit substitution. Compare Lemma 14 of [Tarski] p. 70. The spim 1623 series of theorems requires that only one direction of the substitution hypothesis hold. (Contributed by NM, 5-Aug-1993.) (Revised by Mario Carneiro, 3-Oct-2016.) (Proof rewritten by Jim Kingdon, 10-Jun-2018.)
xψ    &   (x = y → (φψ))       (xφψ)

Theoremspimeh 1624 Existential introduction, using implicit substitition. Compare Lemma 14 of [Tarski] p. 70. (Contributed by NM, 7-Aug-1994.) (Revised by NM, 3-Feb-2015.) (New usage is discouraged.)
(φxφ)    &   (x = y → (φψ))       (φxψ)

Theoremspimed 1625 Deduction version of spime 1626. (Contributed by NM, 5-Aug-1993.) (Revised by Mario Carneiro, 3-Oct-2016.) (Proof shortened by Wolf Lammen, 19-Feb-2018.)
(χ → Ⅎxφ)    &   (x = y → (φψ))       (χ → (φxψ))

Theoremspime 1626 Existential introduction, using implicit substitution. Compare Lemma 14 of [Tarski] p. 70. (Contributed by NM, 7-Aug-1994.) (Revised by Mario Carneiro, 3-Oct-2016.) (Proof shortened by Wolf Lammen, 6-Mar-2018.)
xφ    &   (x = y → (φψ))       (φxψ)

Theoremcbv3 1627 Rule used to change bound variables, using implicit substitution. (Contributed by NM, 5-Aug-1993.) (Proof shortened by Wolf Lammen, 12-May-2018.)
yφ    &   xψ    &   (x = y → (φψ))       (xφyψ)

Theoremcbv3h 1628 Rule used to change bound variables, using implicit substitution. (Contributed by NM, 5-Aug-1993.) (Proof shortened by Andrew Salmon, 25-May-2011.) (Proof shortened by Wolf Lammen, 12-May-2018.)
(φyφ)    &   (ψxψ)    &   (x = y → (φψ))       (xφyψ)

Theoremcbv1 1629 Rule used to change bound variables, using implicit substitution. Revised to format hypotheses to common style. (Contributed by NM, 5-Aug-1993.) (Revised by Mario Carneiro, 3-Oct-2016.) (Revised by Wolf Lammen, 13-May-2018.)
xφ    &   yφ    &   (φ → Ⅎyψ)    &   (φ → Ⅎxχ)    &   (φ → (x = y → (ψχ)))       (φ → (xψyχ))

Theoremcbv1h 1630 Rule used to change bound variables, using implicit substitution. (Contributed by NM, 5-Aug-1993.) (Proof shortened by Wolf Lammen, 13-May-2018.)
(φ → (ψyψ))    &   (φ → (χxχ))    &   (φ → (x = y → (ψχ)))       (xyφ → (xψyχ))

Theoremcbv2h 1631 Rule used to change bound variables, using implicit substitution. (Contributed by NM, 5-Aug-1993.)
(φ → (ψyψ))    &   (φ → (χxχ))    &   (φ → (x = y → (ψχ)))       (xyφ → (xψyχ))

Theoremcbv2 1632 Rule used to change bound variables, using implicit substitution. Revised to align format of hypotheses to common style. (Contributed by NM, 5-Aug-1993.) (Revised by Mario Carneiro, 3-Oct-2016.) (Revised by Wolf Lammen, 13-May-2018.)
xφ    &   yφ    &   (φ → Ⅎyψ)    &   (φ → Ⅎxχ)    &   (φ → (x = y → (ψχ)))       (φ → (xψyχ))

Theoremcbvalh 1633 Rule used to change bound variables, using implicit substitition. (Contributed by NM, 5-Aug-1993.) (Proof shortened by Andrew Salmon, 25-May-2011.)
(φyφ)    &   (ψxψ)    &   (x = y → (φψ))       (xφyψ)

Theoremcbval 1634 Rule used to change bound variables, using implicit substitution. (Contributed by NM, 5-Aug-1993.) (Revised by Mario Carneiro, 3-Oct-2016.)
yφ    &   xψ    &   (x = y → (φψ))       (xφyψ)

Theoremcbvexh 1635 Rule used to change bound variables, using implicit substitition. (Contributed by NM, 5-Aug-1993.) (Revised by Mario Carneiro, 3-Feb-2015.)
(φyφ)    &   (ψxψ)    &   (x = y → (φψ))       (xφyψ)

Theoremcbvex 1636 Rule used to change bound variables, using implicit substitution. (Contributed by NM, 5-Aug-1993.)
yφ    &   xψ    &   (x = y → (φψ))       (xφyψ)

Theoremchvar 1637 Implicit substitution of y for x into a theorem. (Contributed by Raph Levien, 9-Jul-2003.) (Revised by Mario Carneiro, 3-Oct-2016.)
xψ    &   (x = y → (φψ))    &   φ       ψ

Theoremequvini 1638 A variable introduction law for equality. Lemma 15 of [Monk2] p. 109, however we do not require z to be distinct from x and y (making the proof longer). (Contributed by NM, 5-Aug-1993.) (Proof shortened by Andrew Salmon, 25-May-2011.)
(x = yz(x = z z = y))

Theoremequveli 1639 A variable elimination law for equality with no distinct variable requirements. (Compare equvini 1638.) (Contributed by NM, 1-Mar-2013.) (Revised by NM, 3-Feb-2015.)
(z(z = xz = y) → x = y)

Theoremnfald 1640 If x is not free in φ, it is not free in yφ. (Contributed by Mario Carneiro, 24-Sep-2016.) (Proof shortened by Wolf Lammen, 6-Jan-2018.)
yφ    &   (φ → Ⅎxψ)       (φ → Ⅎxyψ)

Theoremnfexd 1641 If x is not free in φ, it is not free in yφ. (Contributed by Mario Carneiro, 24-Sep-2016.) (Proof rewritten by Jim Kingdon, 7-Feb-2018.)
yφ    &   (φ → Ⅎxψ)       (φ → Ⅎxyψ)

1.3.10  Substitution (without distinct variables)

Syntaxwsb 1642 Extend wff definition to include proper substitution (read "the wff that results when y is properly substituted for x in wff φ"). (Contributed by NM, 24-Jan-2006.)
wff [y / x]φ

Definitiondf-sb 1643 Define proper substitution. Remark 9.1 in [Megill] p. 447 (p. 15 of the preprint). For our notation, we use [y / x]φ to mean "the wff that results when y is properly substituted for x in the wff φ." We can also use [y / x]φ in place of the "free for" side condition used in traditional predicate calculus; see, for example, stdpc4 1655.

Our notation was introduced in Haskell B. Curry's Foundations of Mathematical Logic (1977), p. 316 and is frequently used in textbooks of lambda calculus and combinatory logic. This notation improves the common but ambiguous notation, "φ(y) is the wff that results when y is properly substituted for x in φ(x)." For example, if the original φ(x) is x = y, then φ(y) is y = y, from which we obtain that φ(x) is x = x. So what exactly does φ(x) mean? Curry's notation solves this problem.

In most books, proper substitution has a somewhat complicated recursive definition with multiple cases based on the occurrences of free and bound variables in the wff. Instead, we use a single formula that is exactly equivalent and gives us a direct definition. We later prove that our definition has the properties we expect of proper substitution (see theorems sbequ 1718, sbcom2 1860 and sbid2v 1869).

Note that our definition is valid even when x and y are replaced with the same variable, as sbid 1654 shows. We achieve this by having x free in the first conjunct and bound in the second. We can also achieve this by using a dummy variable, as the alternate definition dfsb7 1864 shows (which some logicians may prefer because it doesn't mix free and bound variables). Another alternate definition which uses a dummy variable is dfsb7a 1867.

When x and y are distinct, we can express proper substitution with the simpler expressions of sb5 1764 and sb6 1763.

In classical logic, another possible definition is (x = y φ) x(x = yφ) but we do not have an intuitionistic proof that this is equivalent.

There are no restrictions on any of the variables, including what variables may occur in wff φ. (Contributed by NM, 5-Aug-1993.)

([y / x]φ ↔ ((x = yφ) x(x = y φ)))

Theoremsbimi 1644 Infer substitution into antecedent and consequent of an implication. (Contributed by NM, 25-Jun-1998.)
(φψ)       ([y / x]φ → [y / x]ψ)

Theoremsbbii 1645 Infer substitution into both sides of a logical equivalence. (Contributed by NM, 5-Aug-1993.)
(φψ)       ([y / x]φ ↔ [y / x]ψ)

Theoremsb1 1646 One direction of a simplified definition of substitution. (Contributed by NM, 5-Aug-1993.)
([y / x]φx(x = y φ))

Theoremsb2 1647 One direction of a simplified definition of substitution. (Contributed by NM, 5-Aug-1993.)
(x(x = yφ) → [y / x]φ)

Theoremsbequ1 1648 An equality theorem for substitution. (Contributed by NM, 5-Aug-1993.)
(x = y → (φ → [y / x]φ))

Theoremsbequ2 1649 An equality theorem for substitution. (Contributed by NM, 5-Aug-1993.)
(x = y → ([y / x]φφ))

Theoremstdpc7 1650 One of the two equality axioms of standard predicate calculus, called substitutivity of equality. (The other one is stdpc6 1588.) Translated to traditional notation, it can be read: "x = y → (φ(x, x) → φ(x, y)), provided that y is free for x in φ(x, y)." Axiom 7 of [Mendelson] p. 95. (Contributed by NM, 15-Feb-2005.)
(x = y → ([x / y]φφ))

Theoremsbequ12 1651 An equality theorem for substitution. (Contributed by NM, 5-Aug-1993.)
(x = y → (φ ↔ [y / x]φ))

Theoremsbequ12r 1652 An equality theorem for substitution. (Contributed by NM, 6-Oct-2004.) (Proof shortened by Andrew Salmon, 21-Jun-2011.)
(x = y → ([x / y]φφ))

Theoremsbequ12a 1653 An equality theorem for substitution. (Contributed by NM, 5-Aug-1993.)
(x = y → ([y / x]φ ↔ [x / y]φ))

Theoremsbid 1654 An identity theorem for substitution. Remark 9.1 in [Megill] p. 447 (p. 15 of the preprint). (Contributed by NM, 5-Aug-1993.)
([x / x]φφ)

Theoremstdpc4 1655 The specialization axiom of standard predicate calculus. It states that if a statement φ holds for all x, then it also holds for the specific case of y (properly) substituted for x. Translated to traditional notation, it can be read: "xφ(x) → φ(y), provided that y is free for x in φ(x)." Axiom 4 of [Mendelson] p. 69. (Contributed by NM, 5-Aug-1993.)
(xφ → [y / x]φ)

Theoremsbh 1656 Substitution for a variable not free in a wff does not affect it. (Contributed by NM, 5-Aug-1993.) (Revised by NM, 17-Oct-2004.)
(φxφ)       ([y / x]φφ)

Theoremsbf 1657 Substitution for a variable not free in a wff does not affect it. (Contributed by NM, 5-Aug-1993.) (Revised by Mario Carneiro, 4-Oct-2016.)
xφ       ([y / x]φφ)

Theoremsbf2 1658 Substitution has no effect on a bound variable. (Contributed by NM, 1-Jul-2005.)
([y / x]xφxφ)

Theoremsb6x 1659 Equivalence involving substitution for a variable not free. (Contributed by NM, 5-Aug-1993.) (Proof shortened by Andrew Salmon, 12-Aug-2011.)
(φxφ)       ([y / x]φx(x = yφ))

Theoremnfs1f 1660 If x is not free in φ, it is not free in [y / x]φ. (Contributed by Mario Carneiro, 11-Aug-2016.)
xφ       x[y / x]φ

Theoremhbs1f 1661 If x is not free in φ, it is not free in [y / x]φ. (Contributed by NM, 5-Aug-1993.) (Proof shortened by Andrew Salmon, 25-May-2011.)
(φxφ)       ([y / x]φx[y / x]φ)

Theoremsbequ5 1662 Substitution does not change an identical variable specifier. (Contributed by NM, 5-Aug-1993.) (Revised by NM, 21-Dec-2004.)
([w / z]x x = yx x = y)

Theoremsbequ6 1663 Substitution does not change a distinctor. (Contributed by NM, 5-Aug-1993.) (Revised by NM, 14-May-2005.)
([w / z] ¬ x x = y ↔ ¬ x x = y)

Theoremsbt 1664 A substitution into a theorem remains true. (See chvar 1637 and chvarv 1809 for versions using implicit substitition.) (Contributed by NM, 21-Jan-2004.) (Proof shortened by Andrew Salmon, 25-May-2011.)
φ       [y / x]φ

Theoremequsb1 1665 Substitution applied to an atomic wff. (Contributed by NM, 5-Aug-1993.)
[y / x]x = y

Theoremequsb2 1666 Substitution applied to an atomic wff. (Contributed by NM, 5-Aug-1993.)
[y / x]y = x

Theoremsbiedh 1667 Conversion of implicit substitution to explicit substitution (deduction version of sbieh 1670). New proofs should use sbied 1668 instead. (Contributed by NM, 30-Jun-1994.) (Proof shortened by Andrew Salmon, 25-May-2011.) (New usage is discouraged.)
(φxφ)    &   (φ → (χxχ))    &   (φ → (x = y → (ψχ)))       (φ → ([y / x]ψχ))

Theoremsbied 1668 Conversion of implicit substitution to explicit substitution (deduction version of sbie 1671). (Contributed by NM, 30-Jun-1994.) (Revised by Mario Carneiro, 4-Oct-2016.)
xφ    &   (φ → Ⅎxχ)    &   (φ → (x = y → (ψχ)))       (φ → ([y / x]ψχ))

Theoremsbiedv 1669* Conversion of implicit substitution to explicit substitution (deduction version of sbie 1671). (Contributed by NM, 7-Jan-2017.)
((φ x = y) → (ψχ))       (φ → ([y / x]ψχ))

Theoremsbieh 1670 Conversion of implicit substitution to explicit substitution. New proofs should use sbie 1671 instead. (Contributed by NM, 30-Jun-1994.) (New usage is discouraged.)
(ψxψ)    &   (x = y → (φψ))       ([y / x]φψ)

Theoremsbie 1671 Conversion of implicit substitution to explicit substitution. (Contributed by NM, 30-Jun-1994.) (Revised by Mario Carneiro, 4-Oct-2016.) (Revised by Wolf Lammen, 30-Apr-2018.)
xψ    &   (x = y → (φψ))       ([y / x]φψ)

1.3.11  Theorems using axiom ax-11

Theoremequs5a 1672 A property related to substitution that unlike equs5 1707 doesn't require a distinctor antecedent. (Contributed by NM, 2-Feb-2007.)
(x(x = y yφ) → x(x = yφ))

Theoremequs5e 1673 A property related to substitution that unlike equs5 1707 doesn't require a distinctor antecedent. (Contributed by NM, 2-Feb-2007.) (Revised by NM, 3-Feb-2015.)
(x(x = y φ) → x(x = yyφ))

Theoremax11e 1674 Analogue to ax-11 1394 but for existential quantification. (Contributed by Mario Carneiro and Jim Kingdon, 31-Dec-2017.) (Proved by Mario Carneiro, 9-Feb-2018.)
(x = y → (x(x = y φ) → yφ))

Theoremax10oe 1675 Quantifier Substitution for existential quantifiers. Analogue to ax10o 1600 but for rather than . (Contributed by Jim Kingdon, 21-Dec-2017.)
(x x = y → (xψyψ))

Theoremdrex1 1676 Formula-building lemma for use with the Distinctor Reduction Theorem. Part of Theorem 9.4 of [Megill] p. 448 (p. 16 of preprint). (Contributed by NM, 27-Feb-2005.) (Revised by NM, 3-Feb-2015.)
(x x = y → (φψ))       (x x = y → (xφyψ))

Theoremdrsb1 1677 Formula-building lemma for use with the Distinctor Reduction Theorem. Part of Theorem 9.4 of [Megill] p. 448 (p. 16 of preprint). (Contributed by NM, 5-Aug-1993.)
(x x = y → ([z / x]φ ↔ [z / y]φ))

Theoremexdistrfor 1678 Distribution of existential quantifiers, with a bound-variable hypothesis saying that y is not free in φ, but x can be free in φ (and there is no distinct variable condition on x and y). (Contributed by Jim Kingdon, 25-Feb-2018.)
(x x = y xyφ)       (xy(φ ψ) → x(φ yψ))

Theoremsb4a 1679 A version of sb4 1710 that doesn't require a distinctor antecedent. (Contributed by NM, 2-Feb-2007.)
([y / x]yφx(x = yφ))

Theoremequs45f 1680 Two ways of expressing substitution when y is not free in φ. (Contributed by NM, 25-Apr-2008.)
(φyφ)       (x(x = y φ) ↔ x(x = yφ))

Theoremsb6f 1681 Equivalence for substitution when y is not free in φ. (Contributed by NM, 5-Aug-1993.) (Revised by NM, 30-Apr-2008.)
(φyφ)       ([y / x]φx(x = yφ))

Theoremsb5f 1682 Equivalence for substitution when y is not free in φ. (Contributed by NM, 5-Aug-1993.) (Revised by NM, 18-May-2008.)
(φyφ)       ([y / x]φx(x = y φ))

Theoremsb4e 1683 One direction of a simplified definition of substitution that unlike sb4 1710 doesn't require a distinctor antecedent. (Contributed by NM, 2-Feb-2007.)
([y / x]φx(x = yyφ))

Theoremhbsb2a 1684 Special case of a bound-variable hypothesis builder for substitution. (Contributed by NM, 2-Feb-2007.)
([y / x]yφx[y / x]φ)

Theoremhbsb2e 1685 Special case of a bound-variable hypothesis builder for substitution. (Contributed by NM, 2-Feb-2007.)
([y / x]φx[y / x]yφ)

Theoremhbsb3 1686 If y is not free in φ, x is not free in [y / x]φ. (Contributed by NM, 5-Aug-1993.)
(φyφ)       ([y / x]φx[y / x]φ)

Theoremnfs1 1687 If y is not free in φ, x is not free in [y / x]φ. (Contributed by Mario Carneiro, 11-Aug-2016.)
yφ       x[y / x]φ

Theoremsbcof2 1688 Version of sbco 1839 where x is not free in φ. (Contributed by Jim Kingdon, 28-Dec-2017.)
(φxφ)       ([y / x][x / y]φ ↔ [y / x]φ)

1.4  Predicate calculus with distinct variables

1.4.1  Derive the axiom of distinct variables ax-16

Theoremspimv 1689* A version of spim 1623 with a distinct variable requirement instead of a bound variable hypothesis. (Contributed by NM, 5-Aug-1993.)
(x = y → (φψ))       (xφψ)

Theoremaev 1690* A "distinctor elimination" lemma with no restrictions on variables in the consequent, proved without using ax-16 1692. (Contributed by NM, 8-Nov-2006.) (Proof shortened by Andrew Salmon, 21-Jun-2011.)
(x x = yz w = v)

Theoremax16 1691* Theorem showing that ax-16 1692 is redundant if ax-17 1416 is included in the axiom system. The important part of the proof is provided by aev 1690.

See ax16ALT 1736 for an alternate proof that does not require ax-10 1393 or ax-12 1399.

This theorem should not be referenced in any proof. Instead, use ax-16 1692 below so that theorems needing ax-16 1692 can be more easily identified. (Contributed by NM, 8-Nov-2006.)

(x x = y → (φxφ))

Axiomax-16 1692* Axiom of Distinct Variables. The only axiom of predicate calculus requiring that variables be distinct (if we consider ax-17 1416 to be a metatheorem and not an axiom). Axiom scheme C16' 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. It is a somewhat bizarre axiom since the antecedent is always false in set theory, but nonetheless it is technically necessary as you can see from its uses.

This axiom is redundant if we include ax-17 1416; see theorem ax16 1691.

This axiom is obsolete and should no longer be used. It is proved above as theorem ax16 1691. (Contributed by NM, 5-Aug-1993.) (New usage is discouraged.)

(x x = y → (φxφ))

Theoremdveeq2 1693* Quantifier introduction when one pair of variables is distinct. (Contributed by NM, 2-Jan-2002.)
x x = y → (z = yx z = y))

Theoremdveeq2or 1694* Quantifier introduction when one pair of variables is distinct. Like dveeq2 1693 but connecting xx = y by a disjunction rather than negation and implication makes the theorem stronger in intuitionistic logic. (Contributed by Jim Kingdon, 1-Feb-2018.)
(x x = y x z = y)

TheoremdvelimfALT2 1695* Proof of dvelimf 1888 using dveeq2 1693 (shown as the last hypothesis) instead of ax-12 1399. This shows that ax-12 1399 could be replaced by dveeq2 1693 (the last hypothesis). (Contributed by Andrew Salmon, 21-Jul-2011.)
(φxφ)    &   (ψzψ)    &   (z = y → (φψ))    &   x x = y → (z = yx z = y))       x x = y → (ψxψ))

Theoremnd5 1696* A lemma for proving conditionless ZFC axioms. (Contributed by NM, 8-Jan-2002.)
y y = x → (z = yx z = y))

Theoremexlimdv 1697* Deduction from Theorem 19.23 of [Margaris] p. 90. (Contributed by NM, 27-Apr-1994.)
(φ → (ψχ))       (φ → (xψχ))

Theoremax11v2 1698* Recovery of ax11o 1700 from ax11v 1705 without using ax-11 1394. The hypothesis is even weaker than ax11v 1705, with z both distinct from x and not occurring in φ. Thus the hypothesis provides an alternate axiom that can be used in place of ax11o 1700. (Contributed by NM, 2-Feb-2007.)
(x = z → (φx(x = zφ)))       x x = y → (x = y → (φx(x = yφ))))

Theoremax11a2 1699* Derive ax-11o 1701 from a hypothesis in the form of ax-11 1394. The hypothesis is even weaker than ax-11 1394, with z both distinct from x and not occurring in φ. Thus the hypothesis provides an alternate axiom that can be used in place of ax11o 1700. (Contributed by NM, 2-Feb-2007.)
(x = z → (zφx(x = zφ)))       x x = y → (x = y → (φx(x = yφ))))

1.4.2  Derive the obsolete axiom of variable substitution ax-11o

Theoremax11o 1700 Derivation of set.mm's original ax-11o 1701 from the shorter ax-11 1394 that has replaced it.

An open problem is whether this theorem can be proved without relying on ax-16 1692 or ax-17 1416.

Normally, ax11o 1700 should be used rather than ax-11o 1701, except by theorems specifically studying the latter's properties. (Contributed by NM, 3-Feb-2007.)

x x = y → (x = y → (φx(x = yφ))))

Page List
Jump to page: Contents  1 1-100 2 101-200 3 201-300 4 301-400 5 401-500 6 501-600 7 601-700 8 701-800 9 801-900 10 901-1000 11 1001-1100 12 1101-1200 13 1201-1300 14 1301-1400 15 1401-1500 16 1501-1600 17 1601-1700 18 1701-1800 19 1801-1900 20 1901-2000 21 2001-2100 22 2101-2200 23 2201-2300 24 2301-2400 25 2401-2500 26 2501-2600 27 2601-2700 28 2701-2800 29 2801-2900 30 2901-3000 31 3001-3100 32 3101-3200 33 3201-3300 34 3301-3400 35 3401-3500 36 3501-3600 37 3601-3700 38 3701-3800 39 3801-3900 40 3901-4000 41 4001-4100 42 4101-4200 43 4201-4300 44 4301-4400 45 4401-4500 46 4501-4600 47 4601-4700 48 4701-4800 49 4801-4900 50 4901-5000 51 5001-5100 52 5101-5200 53 5201-5300 54 5301-5400 55 5401-5500 56 5501-5600 57 5601-5700 58 5701-5800 59 5801-5900 60 5901-6000 61 6001-6100 62 6101-6200 63 6201-6300 64 6301-6400 65 6401-6500 66 6501-6600 67 6601-6700 68 6701-6800 69 6801-6900 70 6901-7000 71 7001-7100 72 7101-7200 73 7201-7300 74 7301-7400 75 7401-7500 76 7501-7600 77 7601-7700 78 7701-7800 79 7801-7900 80 7901-8000 81 8001-8100 82 8101-8200 83 8201-8300 84 8301-8400 85 8401-8500 86 8501-8600 87 8601-8700 88 8701-8800 89 8801-8900 90 8901-9000 91 9001-9100 92 9101-9200 93 9201-9300 94 9301-9400 95 9401-9457
 Copyright terms: Public domain < Previous  Next >