Here is the Synopsis:
Proof of "Axioms" of Propositional Logic:
Synopsis.
Willem F. Esterhuyse.
Abstract
We introduce more basic axioms with which we are able to prove some
"axioms" of Propositional Logic. We use the symbols from my other article:
"Introduction to Logical Structures". Logical Structures are graphs with doubly labelled
vertices with edges carrying symbols. The proofs are very mechanical and does not
require ingenuity to construct.
We use new operators called "Attractors" and "Stoppers". An Attractor ( symbol:
"-(" OR ")-") is an edge with a half circle symbol, that can carry any relation symbol.
Axioms for Attractors include A:AA where we have as premise two structures named B
with Attractors carrying the "therefore" symbol facing each other and attached to two
neighbouring structures: B. Because the structures are the same and the Attractors face
each other, and the therefore symbols point in the same direction they annihilate the
structures B and we are left with a conclusion of the empty structure. Like in:
((B)->-( )->-(B)) -> (Empty Structure).
We also have the axiom: A:AtI (Attractor Introduction) in which we have a row of
structures as premise and conclusion of the same row of structures each with an
Attractor attached to them and pointing to the right or left. Like in:
A B C D -> (A)-( (B)-( (C)-( (D)-(.
A:AD distributes the Attractors and cut relations and places a Stopper on the cutted relation (see line 3 below). Stopper = "|-".
Further axioms are: A:SD says that we may drop a Stopper at either end of a line. And
A:ASS says we can exchange Stoppers for Attractors in a line of structures as long as
we replace every instance of the operators.
We can prove: P OR P = P. We prove Modus Ponens as follows:
Line nr. Statement Reason
1 B B -> C Premise
2 B ->-( (B -> C)->-( 1, A:AtI
3 B ->-( )->-(B) |->-(C)->-( 2, A:AD
4 |->-(C)->-( 3, A:AA
5 (C)->-( 4, A:SD
6 (C)->-| 5, A:ASS
7 C 6, A:SD
We can prove AND-elimination, AND-introduction and transposition. We prove
AND introduction (T:ANDI):
1 A B Premise
2 (A)-(x)-( (B) -(x)-( 1, A:AtI
3 (A)-(x)-| (B)-(x)-| 2, A:ASS
4 (A)-(x)-| B 3, A:SD
5 (A)-(x)-( B 4, A:ASS
6 (A)-(x)-(B) 5, T:AL
where "-(x)-" = "AND", and T:AL is a theorem to be proved by reasoning backwards through:
1 A -(x)- B Premise
2 A -(x)- B -(x)-( 1, A:AtI
3 )-(x)-(A) |-(x)-(B)-(x)-( 2, A:AD
4 |-(x)-(A) )-(x)-(B)-(x)-| 3, A:ASS
5 A )-(x)-(B) 4, A:SD.
where the mirror image of this is proved similarly.
Modus Tollens and Syllogism can also be proven with these axioms.
We prove: Theorem (T:O): (A OR A) -> A:
1 A -(+)- A Premise
2 A -(+)- A -(+)-( 1, A:AtI
3 )-(+)-(A) |-(+)-(A)-(+)-( 2, A:AD
4 |-(+)-(A) )-(+)-(A)-(+)-| 3, A:ASS
5 A )-(+)-(A) 4, A:SD
6 A |-(+)-(A) 5, A:ASS
and from this (on introduction of a model taking only structures with truth tables as real)
we can conclude that A holds as required.