Recap on last week. Causal generalisations. Arguments from analogy

Recap on last week…

…evaluating inductive arguments….

….inductive generalisations and  causal generalisations…

…. arguments from analogy and authority

Inductive generalisations:

–  Is the premise true?

–  How large is the sample?

–  How representative is the sample?

–  Beware ‘informal’ heuristics – Is there a counterexample?

Causal generalisations:

–  Is the premise true?

–  How strong is the correlation?

–  Does the causal relation make sense or could it be accidental?

–  What causes what?

Arguments from analogy:

–  are the two things similar?

–  are they similar in respect of something relevant?

–  can we find a disanalogy?

Arguments from authority:

–  who exactly is the source of information?

–  is this source qualified in the appropriate area?

–  is the source impartial in respect of this claim?

–  do other experts make other claims?

This week we shall be looking at…

… the distinction between validity and truth…

…at why validity is important…

….and at evaluating deductive arguments

A good deductive argument is SOUND if and only if it:

(a)  is valid  

AND

(b)  has true premises  

Is the argument sound?

9

Is the argument sound?

10

The truth of the premises is not a matter for logicians or those interested in critical reasoning….

….there are many ways in which we determine the truth or falsehood of premises…

…and these ways do not fall into the scope of a class on critical reasoning