- Quiz #6 posted this afternoon (Weds. 12/7), due by midnight!
- Final project due by midnight Sunday, 12/11
- Group component
- Names!
- Individual component
- Peer evaluation component - for those working in groups
- Email me or come see me with questions
- Final exam (replace your lowest quiz grade) Friday, 12/16
Plan for today
- Focus on arguments from analogy
- Basic structure
- Evaluating premises and argument strength
- Work on examples in groups
- End of class: Course evaluation for recitation component of class
- Volunteer to return completed evaluations and pencils to Shatzel Hall 305?
- If the office is closed for lunch, slide the envelope under the door and leave pencils outside
Takeaway points for today:
- Familiarize yourself with the structure of arguments from analogy and be able to a) critically evaluate the premises and b) assess the arguments' overall strength
- For the quiz tonight, be prepared to answer questions on arguments from analogy, and:
- Various types of scientific trials
- The "drug development pipeline," esp. the relationship between phase of testing and strength of evidence, generalizability, and so on
- The importance of blinding (blind/double-blind studies)
- The difference between subjective and objective measures
Arguments from Analogy
Argument from analogy = def. A type of inductive argument in which one infers on the basis of known/observed similarities between two things (or classes of things) that those two things (or classes of things) share another, unknown similarity.
Basic structure
P1) A and B are alike with respect to w (and x and y...)*
P2) A is (or has) trait z
P3) Being (or having) trait(s) w (and x and y...) is relevant to being or having trait z
C) B also is (or has) trait z
* The person making the argument from analogy won't always make this list of similarities explicit. So, as discussed in lecture, you may have to infer the contents of P1 yourself.
Example:
Kevin is a philosopher and he watches Black Mirror. It follows that Liz probably also watches Black Mirror because she's a philosopher too.
Formalized:
P1) Kevin and Liz are alike insofar as they are both philosophers
P2) Kevin watches Black Mirror
P3) Being a philosopher is relevant to (aka, predictive of, associated with, etc.) watching Black Mirror
C) Liz probably watches Black Mirror, too
Critically evaluating arguments from analogy
- Like other inductive arguments, arguments from analogy can be weak, medium, or strong (logical force).
- To determine the strength of an argument from analogy, we evaluate each premise in turn for acceptability.
- In addition, to evaluating the premises we must consider the extent and relevance of the differences between the two things being compared.
- You can formulate counter-arguments to and reductios of arguments from analogy. We'll discuss these concepts in class on Friday.
Evaluating the premises of an argument from analogy
P1
1. Number of instances compared in P1
In general, more instances compared = stronger analogy
2. Variety of things compared in P1
In general, more variety = stronger analogy
3. Number of shared characteristics in P1
In general, more shared attributes = stronger analogy
P2
Not much to do here besides assess the statement for truth or falsity.
P3
4. Relevance of shared characteristics in predicting the z property.
In general, more relevance = a stronger analogy.
5. Revisit P1 and P3: Consider the number of dissimilar characteristics (vs. number of similar, P1) and the relevance of those different characteristics (vs. relevance of similar, P3) in predicting the z property.
In general, fewer relevant differences between A and B = a stronger analogy.
Step 5 is especially important. Your brain latches on to similarities between things (partly due to confirmation bias). But in order to critically evaluate arguments from analogy, you must also consider the relevant differences between the things being compared. So, force yourself to list the differences! Then, consider whether those differences are relevant to predicting whether something has property z.
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Applying the tests to arguments: a systematic method
- Formalize the argument from analogy
- Remember, the contents of P1 are usually not explicit
- Evaluate P1 and P3 with respect to #1-4
- #5: Make a list of noteworthy differences between the two things being compared
- Compare the list of similarities in P1 to the list of differences you've created with respect to two criteria:
- Number of noteworthy similarities vs. number of differences <-- Less important
- Relevance of those similar vs. different traits to predicting property z (P3 vs. your list of differences) <-- More important
- Finally, based on your assessment of the premises, determine whether the overall argument is weak, medium, or strong
Practice (groups)
a) Put the example in standard form for an argument from analogy
b) After formalizing the argument, make a list of differences (non-shared traits) between the two things being compared
c) Evaluate the premises of the argument using the method described above
d) Determine whether the argument from analogy (overall) is weak, medium, or strong w/r.t. logical force
Do questions from the "More Practice" section of Monday's lecture
Course evaluations:
- Last 10-15 min. of class
- Recitation component of the course only (you will evaluate the lecture on Friday)
Thanks for all your hard work this semester, and good luck with finals!
