PHIL 1200 Lecture Notes - Lecture 2: Modus Ponens
19 Jun 2018
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Arguments “on the hoof” or in the wild, in their natural settings
VS
Arguments that are dressed
Simple arguments: one conclusion
Extended arguments: a main conclusion, and premises offered, and one or more premise is also argued
for
Then we have a main conclusion and one or more sub conclusions
Principal argument: main conclusion plus the premises supporting it
Sub argument: sub conclusion, and premises offered in support of it
-process can be repeated several times
Indicator words
Take care not to overlook arguments, and to correctly identify premises and conclusions in arguments
you’ve come across
Argument schemes: modus ponens
Very general; very common
Premise: if P then Q
Premise: P
Conclusion: Q
Deductively valid scheme. Any argument that fits this scheme will necessarily have a true conclusion, it it
has true premises
Conclusion is usually clear from the context.
Often, it will be obvious when a reason supports a conclusion or sub conclusion
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So, be aware of contexts in which arguments are to be expected, and what sorts of conclusions you can
expect in such contexts
Borderline cases
Cases where it’s not clear whether someone intends to make an argument for a conclusion, or to do
something else, like just expressing an opinion and elaborating on it, or telling a joke
3 points:
Be open about the fact that you’re not certain whether there’s an argument present
When it’s not clear whether an argument has been offered, do dress it as an argument, and determine
whether it would be a good argument if that's what the speaker or writer was meaning to do
Be charitable. When it is not clear whether or not there was an argument offered, and you’ve gone
ahead and dressed the passage as an argument, and it turns out that the argument as you’ve
reconstructed it is a terrible one, avoid attributing that argument to the person who was speaking or
who wrote the passage
In an argument as well as in an explanation, someone is offering reasons for something else
Key difference: almost always, in explanations, the conclusion is already agreed upon
Argument: the central purpose is to try to provide supporting reasons for believing that the conclusion is
true. So normally, arguments show up when the conclusion isn’t already agreed upon.
Complication: sometimes there are arguments within explanations.
Arguments can show up in explanations too
When an explanation refers to an argument a person/group of people accepted, and their
accepting that argument explains their behaviour
Fact or principle used in an explanation isn’t agreed on, and needs support
Someone might accept the facts or the principles we use in our explanation, but they might object that
those facts don’t explain the event in question at all
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