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I have two propositions p and q. So is it legal to write the clause as: q ∧ p ∧ ¬ p I am assuming that, in this case p ∧ ¬ p = F will always be False, hence the clause will become q ∧ F = F resulting the whole clause as False.

triandicAnt
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  • Yes, you are correct – shree.pat18 Nov 13 '15 at 02:17
  • So, what's your question? – Aadit M Shah Nov 13 '15 at 02:19
  • I had confusion whether that clause `q ∧ p ∧ ¬ p' is valid or not !! – triandicAnt Nov 13 '15 at 02:21
  • The clause is [well formed](https://en.wikipedia.org/wiki/Well-formed_formula), that's different from [valid](https://en.wikipedia.org/wiki/Validity), which isn't really what you're thinking of since there is no inference, or since you haven't considered models or semantics. Best. – Tom Nov 16 '15 at 17:18
  • @Tom...so, you are saying, the clause is valid but not sound!! – triandicAnt Nov 17 '15 at 08:10
  • Er, no. I'm saying the clause is well formed, in the language. I don't understand the way you are using the term validity here- what definition did you have in mind? – Tom Nov 20 '15 at 09:03

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