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#1 2010-07-20 08:59:22
- samuel12
- Member
- Registered: 2010-07-17
- Posts: 19
logic
I'm having a few troubles with 'validly deduce'
Here is the question:
Q: For any set S of sentences, if T is a tautology, then you can validly deduce T from S.
Can anyone explain to me what it is to 'validly deduce' something, pretty confused here, cheers 
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#2 2010-07-20 15:17:05
- mathsyperson
- Moderator
- Registered: 2005-06-22
- Posts: 4,900
Re: logic
T is a tautology, so it's always true. Therefore, you can always deduce it no matter what facts you start with.
For example, this is a valid deduction:
"If it rains tomorrow, then 3 is less than 7."
Why did the vector cross the road?
It wanted to be normal.
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