SSH 105 Lecture Notes - Lecture 6: Modus Tollens, Tweety, Modus Ponens
28 Jun 2018
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Lecture 6 6
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More technical way of saying this
When reconstructing an argument, ty to formulate a reconstruction that is well-formed,
has premises that are r/j/r for the author/speaker, and (in the case of inductive arguments)
that is undefeated
How to recognize arguments
- Look for a conclusion (statement that is being supported) and look for premises
(statements offering support)
- Ask yourself: is the author trying to get me to believe something by giving me reasons in
support of it
- If yes- then you’ve got an argument
- If no- then it is probably not an argument
What’s not an argument
1. Descriptive writing
2. Rhetorical writing- this merely asserts one or more conclusions without reasons
Compare
- Work is underway to build a bridge over the river. It is hoped that this bridge will solve
our traffic problems- descriptive writing of facts
- We ought to build a bridge over the river. And we should limit the cars that go on it. And
let’s fix the park while we are at it- rhetorical writing
- We ought to build a bridge over the river, because doing that is the best way to solve the
traffic problems- argument- has premise and claim
Some techniques for identifying conclusions
1. Try to ignore non-argumentative material (such as descriptive writing and rhetorical
writing)
2. Remember that any proposition, on any topic, expressed by any person at any time can be
a conclusion
3. Ask yourself what’s the overall point of the (argumentative portion of the) text/speech?
4. Remember that one text/speech may well contain
a. Several independent arguments
b. Sub-arguments
5. Look for conclusion indicators such as: thus, hence, therefore, entails, implies, it follows
that, we may conclude, this proves that, consequently, so, establishes, shows etc.
6. Remember that conclusion-indicators aren’t always present
7. Remember that conclusions don’t always come last in actual text/speeches, even though
we put them last in standard form
8. Sometimes conclusions aren’t explicitly stated at all
9. Sometimes the conclusion that is explicitly stated isn’t the one the speaker/author is
really arguing for
find more resources at oneclass.com
find more resources at oneclass.com
10. Conclusions can be stated in unclear or obscure ways. When reconstructing the argument
in standard form, try to state the conclusions as clearly and simply as possible
Some techniques for identifying premises
1. Try to ignore non-argumentative material (such as descriptive writing and rhetorical
writing)
2. Remember that any proposition on any topic, expressed by any person, at any time, can
be a premise
3. Ask yourself: what are reasons or evidence being offered by the speaker/author. These
are likely the premises
4. Remember that one text/speech may well contain
a. Several independent arguments
b. Sub-arguments
5. Look for premise- indicators, such as: since, because, given that, for the reason that, on
the basis of __ I conclude that, my reasons are as follows, my evidence is
6. Remember that premise-indicators aren’t always present
7. Remember that premises don’t always come first in actual texts/speeches, even though
we put them first in standard form
8. Sometimes premises aren’t explicitly stated at all
9. Sometimes a premise that is explicitly stated isn’t the one the author really intends to use
in her argument
10. Premises can be stated in very unclear/obscure ways when reconstructing argument in
standard for, try to state the premises as clearly and simply as possible
In cases like these, it is extremely important to go slowly and to follow the principle of charity
Adding implicit remises when reconstructing an argument
- Recall: sometimes authors/speakers don’t explicitly state all their premises. When
reconstructing an argument, we have to determine what implicit premises are
- We must always follow the principle of charity here
Principle of faithfulness: when adding implicit premises, make sure they are consistent with the
intentions of the author/speaker
Principle of charity for implicit premises: when adding implicit premises, add ones that are r/j/r
to believe rather than ones that are obviously false
Implicit premises that are not generalization
- “If god exists then pointless evil does not exist. So, clearly, god does not exist”
- Note the logical form
1. If A then B
2. – B (implicit)
3. A (from 1,2 by modus tollens)
Generalizations
find more resources at oneclass.com
find more resources at oneclass.com
Document Summary
When reconstructing an argument, ty to formulate a reconstruction that is well-formed, has premises that are r/j/r for the author/speaker, and (in the case of inductive arguments) that is undefeated. Look for a conclusion (statement that is being supported) and look for premises (statements offering support) Ask yourself: is the author trying to get me to believe something by giving me reasons in support of it. If no- then it is probably not an argument. What"s not an argument: descriptive writing, rhetorical writing- this merely asserts one or more conclusions without reasons. Work is underway to build a bridge over the river. It is hoped that this bridge will solve our traffic problems- descriptive writing of facts. We ought to build a bridge over the river. And we should limit the cars that go on it. And let"s fix the park while we are at it- rhetorical writing.
