LPL 6.4-6.6 lecture

# LPL 6.4-6.6 lecture - Sub-proofs, strategy, logical truth...

This preview shows pages 1–2. Sign up to view the full content.

Sub-proofs, strategy, logical truth Subproofs : Many of the proofs we will consider will require the use of sub-proofs. The reason that subproofs are helpful, and sometimes necessary, is that the consideration of hypothetical cases can lead you to steps in the proof that would be difficult to get otherwise. When should sub-proofs be used? At this point in the course, with only formal rules for the Boolean connectives and the identity symbol, there are only a few specific cases in which sub-proofs will be needed. Elim (proof by cases) Applying the Elim rule will always require the use of sub-proofs. If you see that one of your premises is a disjunction, it is likely that you will need to build sub-proofs so that you can eventually apply Elim to the disjunction. ¬ Intro (indirect proof) Like Elim , applying the ¬ Intro rule will always require the use of subproofs. If you see that your desired conclusion is a negated statement, or it contains material not found in your premises, then it is likely that a sub-proof

This preview has intentionally blurred sections. Sign up to view the full version.

View Full Document
This is the end of the preview. Sign up to access the rest of the document.

## This note was uploaded on 02/10/2011 for the course PHIL 110 taught by Professor ? during the Spring '06 term at South Carolina.

### Page1 / 2

LPL 6.4-6.6 lecture - Sub-proofs, strategy, logical truth...

This preview shows document pages 1 - 2. Sign up to view the full document.

View Full Document
Ask a homework question - tutors are online