all dogs are mortal fido is a dog so fido is mortal

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All dogs are mortal Fido is a dog So Fido is mortal

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All dogs are mortal Fido is a dog So Fido is mortal. All dogs are mortal Fido is a dog So Fido is mortal All dogs are mammals All mammals are mortal So all dogs are mortal. All dogs are mortal Fido is a dog So Fido is mortal All dogs are mammals All mammals are mortal - PowerPoint PPT Presentation

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Page 1: All dogs are mortal Fido is a dog So Fido is mortal

All dogs are mortalFido is a dogSo Fido is mortal

Page 2: All dogs are mortal Fido is a dog So Fido is mortal

All dogs are mortalFido is a dogSo Fido is mortal

All dogs are mammalsAll mammals are mortalSo all dogs are mortal

Page 3: All dogs are mortal Fido is a dog So Fido is mortal

All dogs are mortalFido is a dogSo Fido is mortal

All dogs are mammalsAll mammals are mortalSo all dogs are mortal

All As are BAll Bs are CSo all As are C

Page 4: All dogs are mortal Fido is a dog So Fido is mortal

All dogs are mortalFido is a dogSo Fido is mortal

All dogs are mammalsAll mammals are mortalSo all dogs are mortal

All As are Ba is A (a has the property A)So a is B

All As are BAll Bs are CSo all As are C

Page 5: All dogs are mortal Fido is a dog So Fido is mortal

All dogs are mortalFido is a dogSo Fido is mortal

All dogs are mammalsAll mammals are mortalSo all dogs are mortal

All As are Ba is A (a has the property A)So a is B

All As are BAll Bs are CSo all As are C

ABC

DMK

Page 6: All dogs are mortal Fido is a dog So Fido is mortal

All dogs are mortalFido is a dogSo Fido is mortal

All dogs are mammalsAll mammals are mortalSo all dogs are mortal

No zebra is a donkey

All As are Ba is A (a has the property A)So a is B

All As are BAll Bs are CSo all As are C

All dogs are mortalFido is a dogSo Fido is mortal

All dogs are mammalsAll mammals are mortalSo all dogs are mortal

All As are Ba is A (a has the property A)So a is B

All As are BAll Bs are CSo all As are C

ABC

DMK

Page 7: All dogs are mortal Fido is a dog So Fido is mortal

All dogs are mortalFido is a dogSo Fido is mortal

All dogs are mammalsAll mammals are mortalSo all dogs are mortal

No zebra is a donkeyAll zebras are not donkeyEvery zebra is not a donkey

All As are Ba is A (a has the property A)So a is B

All As are BAll Bs are CSo all As are C

All dogs are mortalFido is a dogSo Fido is mortal

All dogs are mammalsAll mammals are mortalSo all dogs are mortal

All As are Ba is A (a has the property A)So a is B

All As are BAll Bs are CSo all As are C

ABC

DMK

Page 8: All dogs are mortal Fido is a dog So Fido is mortal

All dogs are mortalFido is a dogSo Fido is mortal

All dogs are mammalsAll mammals are mortalSo all dogs are mortal

No zebra is a donkeyAll zebras are not donkeyEvery zebra is not a donkeyEvery zebra is a zebra

All As are Ba is A (a has the property A)So a is B

All As are BAll Bs are CSo all As are C

All dogs are mortalFido is a dogSo Fido is mortal

All dogs are mammalsAll mammals are mortalSo all dogs are mortal

All As are Ba is A (a has the property A)So a is B

All As are BAll Bs are CSo all As are C

ABC

DMK

Page 9: All dogs are mortal Fido is a dog So Fido is mortal

All dogs are mortalFido is a dogSo Fido is mortal

All dogs are mammalsAll mammals are mortalSo all dogs are mortal

No zebra is a donkey A

All zebras are not donkey A

Every zebra is not a donkey A

Every zebra is a zebra B

All As are Ba is A (a has the property A)So a is B

All As are BAll Bs are CSo all As are C

All dogs are mortalFido is a dogSo Fido is mortal

All dogs are mammalsAll mammals are mortalSo all dogs are mortal

All As are Ba is A (a has the property A)So a is B

All As are BAll Bs are CSo all As are C

ABC

DMK

Page 10: All dogs are mortal Fido is a dog So Fido is mortal

Singular termsAristotle is the father of logicU of A is largeFrank’s father is in townThe men drinking martini in the corner is dangerousThat is badI don’t like bananas

Page 11: All dogs are mortal Fido is a dog So Fido is mortal

Singular termsAristotle is the father of logicU of A is largeFrank’s father is in townThe men drinking martini in the corner is dangerousThat is badI don’t like bananas

General termsIvy universities are very largeFrank’s parents are in townPeople drinking martini in the corner are drunk

Page 12: All dogs are mortal Fido is a dog So Fido is mortal

Singular termsAristotle is the father of logicU of A is largeFrank’s father is in townThe men drinking martini in the corner is dangerousThat is badI don’t like bananas

General termsIvy universities are very largeFrank’s parents are in townPeople drinking martini in the corner are drunk

Mass termsSnow is whiteMight is right

Page 13: All dogs are mortal Fido is a dog So Fido is mortal

Grammatical predicatesAristotle is the father of logicU of A is largeFrank’s father is in townThe men drinking martini in the corner is dangerousThat is badI don’t like bananas

Page 14: All dogs are mortal Fido is a dog So Fido is mortal

Grammatical predicatesAristotle is the father of logicU of A is largeFrank’s father is in townThe men drinking martini in the corner is dangerousThat is badI don’t like bananas

Predicates in PLAristotle is the father of logic (Aristotle has the property of being the father of logic)U of A is large (U of A has the property of being large)Frank’s father is in townThe men drinking martini in the corner is dangerousThat is badI don’t like bananas (I have the property of not liking bananas)

Page 15: All dogs are mortal Fido is a dog So Fido is mortal

Aristotle is the father of logic FaU of A is large LuFrank’s father is in town TfThe men drinking martini in the corner is dangerous DmThat is bad BtI don’t like bananas ~Lv

Predicates in PLAristotle is the father of logic (Aristotle has the property of being the father of logic)U of A is large (U of A has the property of being large)Frank’s father is in townThe men drinking martini in the corner is dangerousThat is badI don’t like bananas (I have the property of not liking bananas)

Page 16: All dogs are mortal Fido is a dog So Fido is mortal

Predicates in PL

One-place (unary) predicates

being odd

being even

being in town

not liking bananas

Page 17: All dogs are mortal Fido is a dog So Fido is mortal

Predicates in PL

One-place (unary) predicates

being odd

being even

being in town

not liking bananas

Two-place (binary) predicates (relations)

being grater than

being equal

Page 18: All dogs are mortal Fido is a dog So Fido is mortal

Predicates in PL

One-place (unary) predicates

being odd

being even

being in town

not liking bananas

Two-place (binary) predicates (relations)

being grater than

being equal

Three-place (ternary) predicates (relations)

being between

Page 19: All dogs are mortal Fido is a dog So Fido is mortal

Predicates in PL

One-place (unary) predicates

being odd

being even

being in town

not liking bananas

Two-place (binary) predicates (relations)

being grater than

being equal

Three-place (ternary) predicates (relations)

being between

Predicates in PL

One-place (unary) predicates (properties)

being odd

being even

being in town

not liking bananas

Two-place (binary) predicates (relations)

being grater than

being equal

Three-place (ternary) predicates (relations)

being between

n –place (n-ary) predicates (relations)

Page 20: All dogs are mortal Fido is a dog So Fido is mortal

7.3E3

a. (Ia & Ba) & Ra∼

Page 21: All dogs are mortal Fido is a dog So Fido is mortal

7.3E3

a. (Ia & Ba) & Ra∼b. (Rc & Bc) & Ic∼

Page 22: All dogs are mortal Fido is a dog So Fido is mortal

7.3E3

a. (Ia & Ba) & Ra∼b. (Rc & Bc) & Ic∼c. (Bd & Rd) & Id

Page 23: All dogs are mortal Fido is a dog So Fido is mortal

7.3E3

a. (Ia & Ba) & Ra∼b. (Rc & Bc) & Ic∼c. (Bd & Rd) & Idd. [(Rb Bb) Ib]∼ ∨ ∨

Page 24: All dogs are mortal Fido is a dog So Fido is mortal

7.3E3

a. (Ia & Ba) & Ra∼b. (Rc & Bc) & Ic∼c. (Bd & Rd) & Idd. [(Rb Bb) Ib]∼ ∨ ∨e. Ib (Id & Ia)⊃

Page 25: All dogs are mortal Fido is a dog So Fido is mortal

7.3E3

a. (Ia & Ba) & Ra∼b. (Rc & Bc) & Ic∼c. (Bd & Rd) & Idd. [(Rb Bb) Ib]∼ ∨ ∨e. Ib (Id & Ia)⊃f. [(Ba & Ia) & (Ib & Bb)] & (Ra Rb)∼ ∼ ∨

Page 26: All dogs are mortal Fido is a dog So Fido is mortal

7.3E3

a. (Ia & Ba) & Ra∼b. (Rc & Bc) & Ic∼c. (Bd & Rd) & Idd. [(Rb Bb) Ib]∼ ∨ ∨e. Ib (Id & Ia)⊃f. [(Ba & Ia) & (Ib & Bb)] & (Ra Rb)∼ ∼ ∨g. Lab & Dac

Page 27: All dogs are mortal Fido is a dog So Fido is mortal

7.3E3

a. (Ia & Ba) & Ra∼b. (Rc & Bc) & Ic∼c. (Bd & Rd) & Idd. [(Rb Bb) Ib]∼ ∨ ∨e. Ib (Id & Ia)⊃f. [(Ba & Ia) & (Ib & Bb)] & (Ra Rb)∼ ∼ ∨g. Lab & Dach. (Laa & Lac) & (Dab & Dad)

Page 28: All dogs are mortal Fido is a dog So Fido is mortal

7.3E3

a. (Ia & Ba) & Ra∼b. (Rc & Bc) & Ic∼c. (Bd & Rd) & Idd. [(Rb Bb) Ib]∼ ∨ ∨e. Ib (Id & Ia)⊃f. [(Ba & Ia) & (Ib & Bb)] & (Ra Rb)∼ ∼ ∨g. Lab & Dach. (Laa & Lac) & (Dab & Dad)i. (Lca Dca) & (Lcd & Dcd)∼ ∨

Page 29: All dogs are mortal Fido is a dog So Fido is mortal

7.3E3

a. (Ia & Ba) & Ra∼b. (Rc & Bc) & Ic∼c. (Bd & Rd) & Idd. [(Rb Bb) Ib]∼ ∨ ∨e. Ib (Id & Ia)⊃f. [(Ba & Ia) & (Ib & Bb)] & (Ra Rb)∼ ∼ ∨g. Lab & Dach. (Laa & Lac) & (Dab & Dad)i. (Lca Dca) & (Lcd & Dcd)∼ ∨j. (Adc Abc) & (Acd & Acb)∼ ∨

Page 30: All dogs are mortal Fido is a dog So Fido is mortal

7.3E3

a. (Ia & Ba) & Ra∼b. (Rc & Bc) & Ic∼c. (Bd & Rd) & Idd. [(Rb Bb) Ib]∼ ∨ ∨e. Ib (Id & Ia)⊃f. [(Ba & Ia) & (Ib & Bb)] & (Ra Rb)∼ ∼ ∨g. Lab & Dach. (Laa & Lac) & (Dab & Dad)i. (Lca Dca) & (Lcd & Dcd)∼ ∨j. (Adc Abc) & (Acd & Acb)∼ ∨k. Acb (Sbc & Rb)

Page 31: All dogs are mortal Fido is a dog So Fido is mortal

7.3E3

a. (Ia & Ba) & Ra∼b. (Rc & Bc) & Ic∼c. (Bd & Rd) & Idd. [(Rb Bb) Ib]∼ ∨ ∨e. Ib (Id & Ia)⊃f. [(Ba & Ia) & (Ib & Bb)] & (Ra Rb)∼ ∼ ∨g. Lab & Dach. (Laa & Lac) & (Dab & Dad)i. (Lca Dca) & (Lcd & Dcd)∼ ∨j. (Adc Abc) & (Acd & Acb)∼ ∨k. Acb (Sbc & Rb)l. (Aab & Aad) & (Lab Lad)∼ ∨

Page 32: All dogs are mortal Fido is a dog So Fido is mortal

7.3E3

a. (Ia & Ba) & Ra∼b. (Rc & Bc) & Ic∼c. (Bd & Rd) & Idd. [(Rb Bb) Ib]∼ ∨ ∨e. Ib (Id & Ia)⊃f. [(Ba & Ia) & (Ib & Bb)] & (Ra Rb)∼ ∼ ∨g. Lab & Dach. (Laa & Lac) & (Dab & Dad)i. (Lca Dca) & (Lcd & Dcd)∼ ∨j. (Adc Abc) & (Acd & Acb)∼ ∨k. Acb (Sbc & Rb)l. (Aab & Aad) & (Lab Lad)∼ ∨m. (Sdc & Sca) Sda⊃

Page 33: All dogs are mortal Fido is a dog So Fido is mortal

7.3E3

a. (Ia & Ba) & Ra∼b. (Rc & Bc) & Ic∼c. (Bd & Rd) & Idd. [(Rb Bb) Ib]∼ ∨ ∨e. Ib (Id & Ia)⊃f. [(Ba & Ia) & (Ib & Bb)] & (Ra Rb)∼ ∼ ∨g. Lab & Dach. (Laa & Lac) & (Dab & Dad)i. (Lca Dca) & (Lcd & Dcd)∼ ∨j. (Adc Abc) & (Acd & Acb)∼ ∨k. Acb (Sbc & Rb)l. (Aab & Aad) & (Lab Lad)∼ ∨m. (Sdc & Sca) Sda⊃n. (Abd & Adb) (Lbd & Ldb)⊃

Page 34: All dogs are mortal Fido is a dog So Fido is mortal

7.3E3

a. (Ia & Ba) & Ra∼b. (Rc & Bc) & Ic∼c. (Bd & Rd) & Idd. [(Rb Bb) Ib]∼ ∨ ∨e. Ib (Id & Ia)⊃f. [(Ba & Ia) & (Ib & Bb)] & (Ra Rb)∼ ∼ ∨g. Lab & Dach. (Laa & Lac) & (Dab & Dad)i. (Lca Dca) & (Lcd & Dcd)∼ ∨j. (Adc Abc) & (Acd & Acb)∼ ∨k. Acb (Sbc & Rb)l. (Aab & Aad) & (Lab Lad)∼ ∨m. (Sdc & Sca) Sda⊃n. (Abd & Adb) (Lbd & Ldb)⊃o. (Lcb & Lba) (Dca & Sca)⊃

Page 35: All dogs are mortal Fido is a dog So Fido is mortal

7.3E3

a. (Ia & Ba) & Ra∼b. (Rc & Bc) & Ic∼c. (Bd & Rd) & Idd. [(Rb Bb) Ib]∼ ∨ ∨e. Ib (Id & Ia)⊃f. [(Ba & Ia) & (Ib & Bb)] & (Ra Rb)∼ ∼ ∨g. Lab & Dach. (Laa & Lac) & (Dab & Dad)i. (Lca Dca) & (Lcd & Dcd)∼ ∨j. (Adc Abc) & (Acd & Acb)∼ ∨k. Acb (Sbc & Rb)l. (Aab & Aad) & (Lab Lad)∼ ∨m. (Sdc & Sca) Sda⊃n. (Abd & Adb) (Lbd & Ldb)⊃o. (Lcb & Lba) (Dca & Sca)⊃p. [(Rc Bc) Ic] [(Lac Lbc) (Lcc Ldc)]∼ ∨ ∨ ⊃ ∼ ∨ ∨ ∨

Page 36: All dogs are mortal Fido is a dog So Fido is mortal

7.3E3

a. (Ia & Ba) & Ra∼b. (Rc & Bc) & Ic∼c. (Bd & Rd) & Idd. [(Rb Bb) Ib]∼ ∨ ∨e. Ib (Id & Ia)⊃f. [(Ba & Ia) & (Ib & Bb)] & (Ra Rb)∼ ∼ ∨g. Lab & Dach. (Laa & Lac) & (Dab & Dad)i. (Lca Dca) & (Lcd & Dcd)∼ ∨j. (Adc Abc) & (Acd & Acb)∼ ∨k. Acb (Sbc & Rb)l. (Aab & Aad) & (Lab Lad)∼ ∨m. (Sdc & Sca) Sda⊃n. (Abd & Adb) (Lbd & Ldb)⊃o. (Lcb & Lba) (Dca & Sca)⊃p. [(Rc Bc) Ic] [(Lac Lbc) (Lcc Ldc)]∼ ∨ ∨ ⊃ ∼ ∨ ∨ ∨q. Rd & [Ra (Rb Rc)]∼ ∨ ∨

Page 37: All dogs are mortal Fido is a dog So Fido is mortal

7.3E3

a. (Ia & Ba) & Ra∼b. (Rc & Bc) & Ic∼c. (Bd & Rd) & Idd. [(Rb Bb) Ib]∼ ∨ ∨e. Ib (Id & Ia)⊃f. [(Ba & Ia) & (Ib & Bb)] & (Ra Rb)∼ ∼ ∨g. Lab & Dach. (Laa & Lac) & (Dab & Dad)i. (Lca Dca) & (Lcd & Dcd)∼ ∨j. (Adc Abc) & (Acd & Acb)∼ ∨k. Acb (Sbc & Rb)l. (Aab & Aad) & (Lab Lad)∼ ∨m. (Sdc & Sca) Sda⊃n. (Abd & Adb) (Lbd & Ldb)⊃o. (Lcb & Lba) (Dca & Sca)⊃p. [(Rc Bc) Ic] [(Lac Lbc) (Lcc Ldc)]∼ ∨ ∨ ⊃ ∼ ∨ ∨ ∨q. Rd & [Ra (Rb Rc)]∼ ∨ ∨r. (Rd & Id) & [((Ra & Ia) (Rb & Ib)) (Rc & Ic)]∼ ∨ ∨

Page 38: All dogs are mortal Fido is a dog So Fido is mortal

Quantifiers

many

a few

few

most

some

at least one

little

much

at most three

all

every

any

each

none

a(n)

not one

whatever

whichever

Page 39: All dogs are mortal Fido is a dog So Fido is mortal

Existential quantifier

There are dogs

At least one thing is a dog

There is at least one thing which is a dog

There is at least one thing which has the property of being a dog

Page 40: All dogs are mortal Fido is a dog So Fido is mortal

Existential quantifier

There are dogs

At least one thing is a dog

There is at least one thing which is a dog

There is at least one thing which has the property of being a dog

xDx

Page 41: All dogs are mortal Fido is a dog So Fido is mortal

Existential quantifier

There are dogs

At least one thing is a dog

There is at least one thing which is a dog

There is at least one thing which has the property of being a dog

xDx

Universal quantifier

Everything is a dog

Each thing is a dog

Each and every thing is a dog

All things are dogs

Anything is a dog

Page 42: All dogs are mortal Fido is a dog So Fido is mortal

Existential quantifier

There are dogs

At least one thing is a dog

There is at least one thing which is a dog

There is at least one thing which has the property of being a dog

xDx

Universal quantifier

Everything is a dog

Each thing is a dog

Each and every thing is a dog

All things are dogs

Anything is a dog xDx

Page 43: All dogs are mortal Fido is a dog So Fido is mortal

Negations of simple quantified sentences

It is not the case that there are dogs

There are no dogs

Nothing is a dog

There is no thing that is a dog

Page 44: All dogs are mortal Fido is a dog So Fido is mortal

Negations of simple quantified sentences

It is not the case that there are dogs

There are no dogs

Nothing is a dog

There is no thing that is a dog

~xDx

Page 45: All dogs are mortal Fido is a dog So Fido is mortal

Negations of simple quantified sentences

It is not the case that there are dogs

There are no dogs

Nothing is a dog

There is no thing that is a dog

~xDx

It is not the case that everything is a dog

Not everything is a dog

Not all things are dogs

Page 46: All dogs are mortal Fido is a dog So Fido is mortal

Negations of simple quantified sentences

It is not the case that there are dogs

There are no dogs

Nothing is a dog

There is no thing that is a dog

~xDx

It is not the case that everything is a dog

Not everything is a dog

Not all things are dogs

~xDx

Page 47: All dogs are mortal Fido is a dog So Fido is mortal

7.4E3

a. Pj ( x)Px⊃ ∀

Page 48: All dogs are mortal Fido is a dog So Fido is mortal

7.4E3

a. Pj ( x)Px⊃ ∀b. ( x)Px Pj∼ ∃ ∨

Page 49: All dogs are mortal Fido is a dog So Fido is mortal

7.4E3

a. Pj ( x)Px⊃ ∀b. ( x)Px Pj∼ ∃ ∨c. ( y)Py (Pj & Pr)∃ ⊃

Page 50: All dogs are mortal Fido is a dog So Fido is mortal

7.4E3

a. Pj ( x)Px⊃ ∀b. ( x)Px Pj∼ ∃ ∨c. ( y)Py (Pj & Pr)∃ ⊃d. ( z)Pz & Pr∼ ∀

Page 51: All dogs are mortal Fido is a dog So Fido is mortal

7.4E3

a. Pj ( x)Px⊃ ∀b. ( x)Px Pj∼ ∃ ∨c. ( y)Py (Pj & Pr)∃ ⊃d. ( z)Pz & Pr∼ ∀e. Pr ( x)Px∼ ⊃ ∼ ∃

Page 52: All dogs are mortal Fido is a dog So Fido is mortal

7.4E3

a. Pj ( x)Px⊃ ∀b. ( x)Px Pj∼ ∃ ∨c. ( y)Py (Pj & Pr)∃ ⊃d. ( z)Pz & Pr∼ ∀e. Pr ( x)Px∼ ⊃ ∼ ∃f. ( y)Py & ( z)Pz∃ ∼ ∀

Page 53: All dogs are mortal Fido is a dog So Fido is mortal

7.4E3

a. Pj ( x)Px⊃ ∀b. ( x)Px Pj∼ ∃ ∨c. ( y)Py (Pj & Pr)∃ ⊃d. ( z)Pz & Pr∼ ∀e. Pr ( x)Px∼ ⊃ ∼ ∃f. ( y)Py & ( z)Pz∃ ∼ ∀g. (Pj Pr) & (Pr ( x)Px)⊃ ⊃ ∀

Page 54: All dogs are mortal Fido is a dog So Fido is mortal

7.4E3

a. Pj ( x)Px⊃ ∀b. ( x)Px Pj∼ ∃ ∨c. ( y)Py (Pj & Pr)∃ ⊃d. ( z)Pz & Pr∼ ∀e. Pr ( x)Px∼ ⊃ ∼ ∃f. ( y)Py & ( z)Pz∃ ∼ ∀g. (Pj Pr) & (Pr ( x)Px)⊃ ⊃ ∀h. ( Pj ( x)Px) & (Pj ( x)Px)∼ ⊃ ∼ ∃ ⊃ ∀

Page 55: All dogs are mortal Fido is a dog So Fido is mortal

7.4E3

a. Pj ( x)Px⊃ ∀b. ( x)Px Pj∼ ∃ ∨c. ( y)Py (Pj & Pr)∃ ⊃d. ( z)Pz & Pr∼ ∀e. Pr ( x)Px∼ ⊃ ∼ ∃f. ( y)Py & ( z)Pz∃ ∼ ∀g. (Pj Pr) & (Pr ( x)Px)⊃ ⊃ ∀h. ( Pj ( x)Px) & (Pj ( x)Px)∼ ⊃ ∼ ∃ ⊃ ∀i. ( y)Sy & ( y)Py∀ ∼ ∀

Page 56: All dogs are mortal Fido is a dog So Fido is mortal

7.4E3

a. Pj ( x)Px⊃ ∀b. ( x)Px Pj∼ ∃ ∨c. ( y)Py (Pj & Pr)∃ ⊃d. ( z)Pz & Pr∼ ∀e. Pr ( x)Px∼ ⊃ ∼ ∃f. ( y)Py & ( z)Pz∃ ∼ ∀g. (Pj Pr) & (Pr ( x)Px)⊃ ⊃ ∀h. ( Pj ( x)Px) & (Pj ( x)Px)∼ ⊃ ∼ ∃ ⊃ ∀i. ( y)Sy & ( y)Py∀ ∼ ∀j. ( x)Sx ( x)Px∀ ⊃ ∀

Page 57: All dogs are mortal Fido is a dog So Fido is mortal

7.4E3

a. Pj ( x)Px⊃ ∀b. ( x)Px Pj∼ ∃ ∨c. ( y)Py (Pj & Pr)∃ ⊃d. ( z)Pz & Pr∼ ∀e. Pr ( x)Px∼ ⊃ ∼ ∃f. ( y)Py & ( z)Pz∃ ∼ ∀g. (Pj Pr) & (Pr ( x)Px)⊃ ⊃ ∀h. ( Pj ( x)Px) & (Pj ( x)Px)∼ ⊃ ∼ ∃ ⊃ ∀i. ( y)Sy & ( y)Py∀ ∼ ∀j. ( x)Sx ( x)Px∀ ⊃ ∀k. ( x)Sx ( y)Py∀ ⊃ ∃

Page 58: All dogs are mortal Fido is a dog So Fido is mortal

“And I haven’t seen the two Messengers either. They’ve both gone to the town. Just look along the road and tell me if you can see either of them.”

“I can see nobody on the road”, said Alice.

“I only wish I had such eyes”, the King remarked in a fretful tone. “To be able to see Nobody! And at that distance too!. Why it’s as much as I can do to see real people by this light!”

“Who did you pass on the road?” the King went on, holding out his hand to the Messenger for some hay.

“Nobody”, said the Messenger.

“Quite right”, said the King, “this young lady saw him too. So of course nobody walks slower than you.”

“I do my best”, the Messenger said in a sullen tone, “I’m sure nobody walks much faster than I do!”

“He can’t do that”, said the King, “or else he’d have been first.”