See UNISA – Summary of 2010 Posts for a list of related UNISA posts. This post is in addition to three summary posts I am building over the next couple of months … in this case we are focusing on formal proofs and re-enforcing some of the concepts we have covered in the summary posts.
The content I am covering and trying to wrap my brain around at the moment is the deductive system F also known as the system of natural deduction or principles of reasoning. Our companion will be the tool “Fitch”, which allows us to construct and evaluate formal proofs.
|Step 2-4 and 5-6 are two sub proofs, one for each of the two disjuncts.
2-4 is a disjunction elimination example.
5-6 is a disjunction introduction example.
Lines 4 & 6 bring us to the goal, hence completing the proof.
|The example shows that by proving a contradiction ^ on the basis if an additional assumption (line 2), we can infer Ø from the original premise.|
Next journey will be to the planet of “Conditionals” …