Use mathematical logic to prove this proposition

AI Thread Summary
The discussion focuses on proving the proposition A implies C given the premises A implies B and B implies C, using axioms from a Hilbert System without employing the deduction theorem or Modus Ponens. The axioms provided include implications that form the basis for the proof structure. The proof is constructed by relabeling the variables and applying the axioms systematically to derive the desired conclusion. Key steps involve utilizing the axioms to establish the relationships between the propositions. The conclusion confirms that A implies C follows logically from the initial premises.
solakis1
Messages
407
Reaction score
0
Given the following axioms:
1) ##P\implies(Q\implies P)##
2) ##((P\implies(Q\implies R))\implies((P\implies Q)\implies(P\implies R))## Where ##P,Q,R## are any formulas
3)##(\neg P\implies\neg Q)\implies (Q\implies P)## then prove:

##\{A\implies B,B\implies C\}|- A\implies C##
Without using the deduction theorem and as a rule of inference M.ponens
 
Last edited by a moderator:
Mathematics news on Phys.org
Your OP outlines the axioms of a Hilbert System. Go to the wiki page on Hilbert Systems and search "(HS2)" to see a proof of the following proposition from those axioms using Modus Ponens as rule of inference.
$$(p \to q) \to ((q \to r) \to (p \to r))$$
Relabel ##p,q,r## as ##A,B,C## to get
$$(A \to B) \to ((B \to C) \to (A \to C))$$
Then we have:
\begin{align}
&\vdash(A \to B) \to ((B \to C) \to (A \to C))\\
(A \to B), (B \to C)&\vdash(A \to B) \to ((B \to C) \to (A \to C))\\
(A \to B), (B \to C)&\vdash A\to B\quad\quad\textrm{[1st axiom]}\\
(A \to B), (B \to C)&\vdash(B \to C) \to (A \to C)
\quad\quad\textrm{[Modus Ponens on 3, 2]}\\
(A \to B), (B \to C)&\vdash B\to C \quad\quad\textrm{[2nd axiom]}\\
(A \to B), (B \to C)&\vdash A \to C
\quad\quad\textrm{[Modus Ponens on 5, 4]}
\end{align}
 
Thread 'Video on imaginary numbers and some queries'
Hi, I was watching the following video. I found some points confusing. Could you please help me to understand the gaps? Thanks, in advance! Question 1: Around 4:22, the video says the following. So for those mathematicians, negative numbers didn't exist. You could subtract, that is find the difference between two positive quantities, but you couldn't have a negative answer or negative coefficients. Mathematicians were so averse to negative numbers that there was no single quadratic...
Insights auto threads is broken atm, so I'm manually creating these for new Insight articles. In Dirac’s Principles of Quantum Mechanics published in 1930 he introduced a “convenient notation” he referred to as a “delta function” which he treated as a continuum analog to the discrete Kronecker delta. The Kronecker delta is simply the indexed components of the identity operator in matrix algebra Source: https://www.physicsforums.com/insights/what-exactly-is-diracs-delta-function/ by...
Thread 'Unit Circle Double Angle Derivations'
Here I made a terrible mistake of assuming this to be an equilateral triangle and set 2sinx=1 => x=pi/6. Although this did derive the double angle formulas it also led into a terrible mess trying to find all the combinations of sides. I must have been tired and just assumed 6x=180 and 2sinx=1. By that time, I was so mindset that I nearly scolded a person for even saying 90-x. I wonder if this is a case of biased observation that seeks to dis credit me like Jesus of Nazareth since in reality...
Back
Top