Lecture 15A: Arguments from Analogy

Business: 
1.  Tests back at the end of class. (Explanation of)
2.  Go through/questions about take-home final.


Arguments From Analogy
A.  Literary Analogies vs Arguments from Analogies

Examples of Literary Analogies (used to compare two things)
1.  You are as annoying as nails on a chalkboard.
2.  Your smile is like the sun.
3.  He's like a rock.
4.  Life is like a box of chocolates. You never know what you're gonna get.


Examples of Arguments from Analogies (used to argue for a conclusion: because 2 things are similar in several respects, they must be similar in further respects.)
1. Empty your mind, be formless. Shapeless, like water. If you put water into a cup, it becomes the cup. You put water into a bottle and it becomes the bottle. You put it in a teapot, it becomes the teapot. Now, water can flow or it can crash. Be water, my friend.” ― Bruce Lee

2.  Being a good critical thinker is like being a good musician.  The more you practice, the better you get.  (HC) So, if you want to be a good critical thinker, you need to practice a lot.

3.  Cheerleading should be considered a sport.  Cheerleading requires strength, flexibility, hard training, and a high level of fitness.

4.  Teleological Argument: A watch is a mechanism of exquisite complexity with numerous moving parts precisely arranged and accurately adjusted to achieve a purpose--a purpose imposed by the watch's designer.  Likewise, the universe has exquisite complexity with countless parts--from atoms to asteroids--that fit together precisely and accurately to produce certain effects as though arranged by a plan.  Therefore, the universe must also have a designer.

5.  Cosmological Argument (variation):  A house couldn't have always existed and spontaneously appeared out of nothing, therefore the universe couldn't have always existed and spontaneously appeared.  Since the house needs a builder to explain its existence, so does the universe.

Formal Structure:
(P1)  A and B share attributes w, x, y.
(HP2)  Attributes w, x, and y are relevant to/predictive of having attribute z.
(P3)  A has attribute z.
(C)  B has attribute z.

In normal speech, people rarely explicitly list the ways in which two things are alike as in (P1); it's usually implicit.   (P2) is almost always implicit but it is the most important premise in terms of the strength of the argument. (P3) is often explicit.

Evaluating Analogies:
The best way to evaluate an analogy is to rewrite it into its standard form as ask yourself if each premise is true.  The strength of an analogy usually rests upon the truth of (HP3).

Here are the main criteria you can use to evaluate an analogy:
A.  Relevant similarities:  Do the two things being compared share relevant similarities?  The more relevant similarities there are, the more likely the it is that the analogy is strong.

E.g.  Gasoline is almost as transparent as water and it's also a liquid.  Therefore, if I fill this glass with gasoline, I'll be able to see through it.

B.  Relevant dissimilarities: Are there many relevant dissimilarities between the two things being compared? The more relevant dissimilarities there are, the weaker the analogy.

E.g.,  Gasoline is almost as transparent as water and it's also a liquid.  Water is a delicious drink, so gasoline must be too.

C.  Number of Instances Being Compared:  The greater the number of instances being compared to establish the relationship between w, x, y and z, the stronger the analogy.

E.g., In the teleological argument we can apply the reasoning not just to watches to show that 'complexity' is predictive of having a designer, we can come up with many instances that confirm this principle (e.g., computers, cars, houses, etc...).

E.g.,  Object 1 has properties w, x, y, and also z.  Object 2 has properties w, x, y, and also z.  Object 3 has properties w, x, y, and also z. (HP3) having properties w, x, y is strongly predictive of having property z.  Since Object 4 has properties w, x, y (C) it must also have property z.

D.  Diversity Among Cases:  The greater the diversity among cases that exhibit the relevant similarities (i.e., establish that properties w, x, y are relevant to having property z), the stronger the argument.

Common uses:
Arguments from analogy are often used to argue that
(1) a new policy/idea/plan will or won't work because it shares relevant characteristics with a previous policy/idea/plan;
(2) a something is good/bad/beautiful/ugly (i.e., value judgements) because it shares relevant characteristics with something we ascribe those values to.

A counter to an argument from analogy hinges on showing that having one set of properties (p, q, r, z) doesn't mean that every object with properties p, q, and r will also necessarily have property z.
In the case of the argument from design, another major flaw is that there is a disanalogy between inanimate objects which are unable to pass on complexity and living organisms which are able to reproduce and pass on complexity (and possibly become more complex over time). Disanalogies arise when we show that the properties under consideration (complexity and purposefulness) aren't necessarily relevant to having some other property (intelligent designer).

HW 15A
p. 286 Ex 11B  2. (b) 3. (a), (b), (c), (d)