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Owen

['Member']Joined: November 15, 2016 at 11:35Last active: June 03, 2019 at 03:23None discussions24 comments

Comments

In: Can a tautology break the law of non-contradiction?  — view comment
#2, It's false to claim that (A V A) is a tautology unless A is a tautology (A v A)<=> A, is tautologous.
April 06, 2019 at 13:32
In: Burned out by logic Intro book  — view comment
(p->q & q) <-> q <-> (q -> p)
December 29, 2018 at 10:30
In: Burned out by logic Intro book  — view comment
(p->q & q) -> p, is invalid. It is false when p=F and q=T. T T T T T F T T F F T F F T T F F F T F
December 27, 2018 at 11:42
In: Logical consequence  — view comment
Tautologies are logical truths. In virtue of truth tables (p & q) -> q is a tautology. and ((p -> q) & p) <-> (p & q), is a tautology. therefore ((p -...
October 19, 2018 at 12:31
In: Law of Identity  — view comment
1, x=y defined: E!x & E!y & (All F)(Fx <-> Fy). and 2. E!x defined: (Some F)(Fx). 3. (All x)(x=x <-> E!x), is a theorem. If either or both do not exis...
October 13, 2018 at 23:13
In: Is this argument form valid ? (contradiction through disjunctive syllogism)  — view comment
((P V Q) & (P -> ~R) & (Q -> ~R)) -> ~R, is tautologous. T T T F T F F F T F F T F F T F T F F F F F F F F F F F Because ((P V Q) & (P -> ~R) & (Q -> ...
August 24, 2018 at 11:59
In: Is this argument form valid ? (contradiction through disjunctive syllogism)  — view comment
(P v Q) & ~P & ~Q, is a contradiction. ((T v T) & F & F) = F ((F v T) & T & F) = F ((T v F) & F & T) = F ((F v F) & T & T) = F.
August 23, 2018 at 11:33
In: The modalities of truth  — view comment
1."A" is necessarily true iff "not-A -> (B and not-B)", is invalid. It fails when "A" is necessarily true if "not-A -> (B and not-B)". (not-A -> (B an...
May 30, 2018 at 19:12
In: The modalities of truth  — view comment
It is false to say 'possible A' claims 'A or not A'. It is false to say 'A or not A' is contingent. 'A or not A' is tautologous, necessarily true.
May 30, 2018 at 13:39
In: Defining logic  — view comment
Not (The apple is red) <-> The apple is not red, is not valid. It fails in the case of no apples...as you have noted. (Not (The apple is red) <-> The ...
April 17, 2018 at 09:54
In: "All statements are false" is NOT false!?!  — view comment
Ep(p). (All statements are false) is false, and it is equivalent to (Some statements are true). 1. (All p)(~p) -> ~q. 2. (All p)(~p) -> ~(~q). 3. (All...
September 18, 2017 at 19:20
In: Impossible being  — view comment
~E!(the x: Fx & ~Fx).
August 20, 2017 at 13:27
In: Existence is not a predicate  — view comment
"For "Ga" to be a wff, doesn't a have to be an object in your domain of discourse?" Vulcan rotates. Pegasus flies. Santa wears a red suit. Etc. are fa...
July 24, 2017 at 20:21
In: Existence is not a predicate  — view comment
Of course 'exists' is a predicate. 'a exists', has 'a' as its subject and 'exists' as its predicate. But, exists is not a primary predicate. (Ga & (a ...
July 24, 2017 at 19:22
In: Ontology of a universe  — view comment
"Existence in the most general sense means being identical to oneself and different from others." I agree that: x exists <-> x=x x exists <-> Ey(x=y) ...
May 29, 2017 at 18:10
In: Ontology of a universe  — view comment
Srap Tasmaner... Suppose I claim there is a smallest positive real number, call it k. It's easily proven that k < 1, right? Does that prove that there...
May 29, 2017 at 12:01
In: Ontology of a universe  — view comment
Vulcan does not exist. Pegasus does not exist. Santa does not exist. etc. Sometimes naming does not bring things into existence.
May 28, 2017 at 16:37
In: Ontology of a universe  — view comment
HI Srap Tasmaner. 1. Ga -> ?x(Gx), is valid. 2. Ga -> ?F(Fa), is valid. 3. Ga -> ?x?F(Fx) is valid. 1 is 1st order and 2 and 3 are 2nd order theorems....
May 28, 2017 at 10:42
In: Ontology of a universe  — view comment
If it is true that unicorns have four legs then unicorns exist. Truth is that which can be shown to be the case. To show that 'Unicorns have four legs...
May 27, 2017 at 23:29
In: Ontology of a universe  — view comment
noAxioms.. F is a variable predicate of individuals x (some F)(Fx) means there is at least one instance of F such that Fx is true. ie. Ax v Bx v Cx .....
May 27, 2017 at 17:47
In: Ontology of a universe  — view comment
noAxioms... x exists =def (some F)(Fx). Descartes exists <-> (some F)(F(Descartes)). If Descartes has a particular predicate such as 'thinks' (Descart...
May 27, 2017 at 15:13
In: Is unrestricted omnipotence immune to all contradictions?  — view comment
Even with 'logical consistency' there is no omnipotent being. We prove what does not exist by showing a logical contradiction, expressed as "P and not...
May 23, 2017 at 14:59
In: Ontology of a universe  — view comment
'I think, therefore I'm possible' is a tautology. 1. I think, therefore I am. Gx -> (some F)(Fx). 2. I am therefore It's possible that I am. (some F)(...
May 22, 2017 at 14:26
In: Is 'I think therefore I am' a tautology?  — view comment
Yes 'I think therefore I am' is an instance of the tautology: Gx -> EF(Fx), for all x. 'I think' has the form Gx. I am has the form EF(Fx). If x has t...
May 06, 2017 at 13:49
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