• Remember this argument?

• • • • • • 1. She who has learned medicine practices an art and acts in accordance with that art.

2. Similarly, she who has learned justice practices an art.

∵ 3. She who has learned justice acts in accordance with her art, i.e., is just.

4. The orator has learned justice.

∴ 5. The orator is just.

∴ 6. The orator will “never want to do what’s unjust” (19).

• • • 1. She who has learned medicine practices an art and acts in accordance with that art.

2. Similarly, she who has learned justice practices an art.

∵ 3. She who has learned justice acts in accordance with her art, i.e., is just.

• This part of the argument is an analogical argument.

• To draw an analogy between two things x and y is to indicate at least one respect in which x is similar to y.

Examples: • • • Swordplay is a dance of sorts, an understanding of the logical, most sophisticated next step. (Lisa Tawn Bergren) As smoking is to the lungs, so is resentment to the soul; even one puff is bad for you. (Elizabeth Gilbert) Sports is to war as pornography is to sex. (Jonathan Haidt)

Analogies can be useful for: • • • Literary flourishes Explanation Arguments

Literary flourishes: • You ain’t nothin but a hound dog.

Explanation: • The atom is like a little solar system: in an atom, electrons orbit a nucleus of protons and neutrons; similarly, in a solar system, planets orbit a star.

Argument • Three of my friends bought their computers on the internet and they were all unhappy with them. I was thinking about ordering my new computer online but now it looks like if I do, I’ll be unhappy with it.

An analogical argument is an argument with the following traits: • Some of its premises draw an analogy between (indicate properties shared by) multiple things x 1 ,

x

2 ,…,x n and y; • Other premises ascribe some further property P to

x

1 , x 2 ,…,x n ; and • The conclusion ascribes P to y.

• Three of my friends bought their computers on the internet and they were all unhappy with them. I was thinking about ordering my new computer online but now it looks like if I do, I’ll be unhappy with it.

•

Some of its premises draw an analogy between (indicate properties possessed by) multiple things x 1 , x 2 ,…,x n and y.

• • • • x 1 : computer bought by friend 1 x 2 : computer bought by friend 2 x 3 : computer bought by friend 3 y: computer I was thinking of buying • Property possessed by x 1 , x 2 ,…,x n the internet.

and y: being bought on

• Three of my friends bought their computers on the internet and they were all unhappy with them. I was thinking about ordering my new computer online but now it looks like if I do, I’ll be unhappy with it.

•

Other premises ascribe some further property P to x 1 , x 2 ,…,x n .

• Further property P: displeasing owner.

• Three of my friends bought their computers on the internet and they were all unhappy with them. I was thinking about ordering my new computer online but now it looks like if I do, I’ll be unhappy with it.

•

The conclusion ascribes P to y.

• y: the computer I’m thinking of buying.

• P: displeasing owner.

• Ascription of P to y: I’ll be unhappy with the computer I was thinking about ordering.

Identify the three traits of an analogical argument in each of the following arguments.

• There might be life on Europa because it has an atmosphere that contains oxygen just like the Earth.

• I am scared to let Susan see me in this sweater. A couple of my other friends told me it makes me look like a child, and she’s at least as critical as they are.

• A watch could not assemble itself, because it itself either.

’ s too complex. The universe is at least as complex as a watch. So the universe could not have assembled

• There might be life on Europa because it has an atmosphere that contains oxygen just like the Earth.

• • • • • x: Earth y: Europa Property possessed by x and y: having an atmosphere that contains oxygen P: supporting life Ascription of further property to y: there might be life on Europa.

• I am scared to let Susan see me in this sweater. A couple of my other friends told me it makes me look like a child, and she’s at least as critical as they are.

• • • • • •

x

1 : friend 1

x

2 : friend 2 y: Susan Property possessed by x 1 , x 2 , y: being critical to a particular degree.

P: thinking the sweater makes me look like a child Ascription of P to y: Susan will think the sweater will make me look like a child.

• A watch could not assemble itself, because it itself either.

’ s too complex. The universe is at least as complex as a watch. So the universe could not have assembled • • • • x: a watch y: the universe Property possessed by both x and y: complexity P: non-self-assemblingness

Exercise • Come up with your own inductive argument for the conclusion that Austin is hot in the summer.

• The strength of an analogical argument is determined by six factors.

• Factor 1: Number of entities All things being equal, when inferring by analogy that object y has attribute P, the more entities to which we draw an analogy with y, the stronger our analogical argument.

• From the earlier example, if our computer buyer had 10 friends who were unhappy with the computers they purchased on the internet, the argument would be stronger.

• Factor 2: Variety of entities All things being equal, the more varied are x 1 , x 2 ,…,x n (the objects analogized to y in the premises) the stronger our analogical argument. • Consider processor speed. If we don ’ t know the speed of the processor in the target, we want a large diversity of processors in our sample.

• Factor 3: Number of similar respects All things being equal, the more attributes are shared by x 1 , x 2 ,…,x n , on the one hand and y on the other, the stronger the analogical argument.

• If all of our friends ’ computers were the same brand as the one we are buying, the analogy gets stronger. If they all ordered from the same company that we are going to use, the analogy gets stronger.

• Factor 4: Relevance The respects in which the premise objects x 1 , x 2 ,…,x n are similar to the conclusion object y should be relevant to whether the conclusion object is P. That is, there should be causal relations of some kind between, on the one hand, P 1 , P 2 ,…,P m and P.

• If we found out that only inept manufacturers chose to sell on the internet, then the argument would be stronger.

• Factor 5: Absence of relevant disanalogies If we can point to other attributes such that: x 1 , x 2 ,…,x n possess them; y does not possess them; and they are plausibly relevant to x 1 , x 2 ,…,x n ’s being P, then our analogical argument is significantly weakened.

• If all the friends bought one type of computer and you are considering a different type, the analogy gets weaker. If theirs were refurbished and yours will be new, the analogy gets weaker.

• Factor 6: Modesty The more modest the conclusion relative to the premises, the stronger the analogical argument.

• Consider these two conclusions: (1) I will be terribly unhappy with my computer, (2) I will be less than perfectly pleased with my computer.

Exercise • Keeping in mind the six traits of a good analogical argument, can strengthen this argument: Brad Pitt is an actor and is rich.

Oprah Winfrey is an actor and is rich.

Sophia Vergara is an actor.

∵ Sophia Vergara is rich too.

Exercise • How might you strengthen this argument?

• • • 1. She who has learned medicine practices an art and acts in accordance with that art.

2. Similarly, she who has learned justice practices an art.

∵ 3. She who has learned justice acts in accordance with her art, i.e., is just.