Part I: Mill’s Methods redux Part II: Analogical Reasoning

Homework

• Informal Fallacies• pp. 103-105, §4.1 “Fallacies in General” • pp. 121-131, §4.3 “Fallacies of Weak Induction”

• Review:– Induction

» Analogical Reasoning, e.g., ex. 8.4» Causal Argumentation, e.g., 8.3b» Inductive Generalization, e.g., 8.2b

Mill’s Methods

1. Agreement

2. Difference– (Agreement & Difference)

3. Concomitant Variation

4. Residue

Typically establishes sufficient conditions

Establishes variable relations

Establishes partial causation

A causal conclusion is strong to the degree that it is supported by premises with evidence of one or more

of Mill’s methods (p. 79)

Mill's Method: Concomitant Variation

• Concomitant Variation– A first discovery: the volume knob

– If variations in phenomenon E coincide with variations in phenomenon P, then it is probable that E and P are causally related. (p. 75)

Mill’s Methods: Residue

Characteristic features1. Deals with complex phenomena

2. Established knowledge of some causal factorsa) in measured quantities

Subtract from any phenomenon such part as is known by previous inductions to be the effect of certain antecedents, and the residue (i.e., remaining parts) of the phenomenon is the effect of the remaining antecedents

Mill’s Method: Residue

After realizing a loss of $100,000 a department store’s chief accountant could suggest only three causes: an excessive number of clerks, increases in utility rates, and damage to merchandise caused by a flood. These expenses were estimated at $25,000, $30,000 and $10,000 respectively. Since no other ordinary sources could be found, the accountant attributed the remaining $35,000 to shoplifting.

Mill's Method: Residue

After realizing a loss of $100,000 a department store’s chief accountant could suggest only three causes: an excessive number of clerks, increases in utility rates, and damage to merchandise caused by a flood. These expenses were estimated at $25,000, $30,000 and $10,000 respectively. Since no other ordinary sources could be found, the accountant attributed the remaining $35,000 to shoplifting.

Is there sufficient evidence for this attribution?

Fallacious: weak induction

ANALOGICAL REASONINGInduction – Final Unit

Analogical Reasoning

• Reasoning that depends on a comparison– Typically two things, i.e., events, states of affairs,

practices, etc.

Common Properties

Inferred Property

Point of Comparison

Analogical Reasoning

Analogical Reasoning

1. Common features relevantly similar to inferred featurea) Number (extent) of these similarities

i. Diversity among common features

2. No relevant dissimilarities (disanalogy)

Factors Affecting Strength

Analogical Reasoning

1. Relevance of similarities to inferred feature– Causal connection:• I’m allergic to hornet stings. Their venom causes me to

swell up and sometimes I come close to losing consciousness. Yellow jackets aren’t as aggressive as hornets, but they’re both stinging bees and have a similar venom. I’ve not been stung by a yellow jacket. Nevertheless, I’ll keep away from it. I’m probably allergic to its sting as well.– Subject: Yellow Jacket stings– Analogue: Hornet stings– Common features: stinging bee, wasp family, venom– Inferred feature: allergic reaction to venom

Factors Affecting Strength

Analogical Reasoning

1. Relevance of similarities to inferred feature– Statistical connection:

• Large classrooms like Memorial Hall traditionally have attendance rates at less than 50% of total. This is, in fact, especially true of the freshman/sophomore classes, and classes that meet early in the morning. Logic 120, a class typically taken by lower classmen, is also held in a large classroom in the student center early in the morning. I suspect that this class also has a low average attendance as well, likely below 50%.– Subject: classroom in Student Center (attendance)– Analogue: Memorial Hall (attendance)– Common features: frosh/soph class, meeting time– Inferred feature: low attendance

Factors Affecting Strength

Analogical Reasoning

1. Relevance of similarities to inferred feature– Aesthetic similarity:• I enjoy Stephen King’s novels. They are quick, easy

reads but really gripping horror stories. He’s coming out with a new book, and I think it will be good too. – Subject: Stephen King’s new book– Analogue: his previous novels (horror stories)– Common features: authorship, genre

» “quick and easy,” “gripping”– Inferred feature: quality of the work (enjoyment)

Factors Affecting Strength

Analogical Reasoning

2. Disanalogies– A dissimilarity between subject and analogue is

relevant to the inference• Differences of kind

• Feature possessed by analogue but not subject

Though Jones tends to struggle with his class work, he is a good student in art class. His random-abstract learning style seems suited the subject. You know, I just noticed that he has logic right after art class. So I think he’ll do well in logic also.

Factors Affecting Strength

Comparable Entities?

My dog

Dog?

Argument

Both my dog and my neighbor's dog are well-loved members of the family. Each one is well fed, house broken, walked on a regular basis. My dog has a very calm temperament. So I infer that my neighbor's dog also has a calm temperament.

Homework

• Informal Fallacies• pp. 103-105, §4.1 “Fallacies in General” • pp. 121-131, §4.3 “Fallacies of Weak Induction”

• Review:– Induction

» Analogical Reasoning, e.g., ex. 8.4» Causal Argumentation, e.g., 8.3b» Inductive Generalization, e.g., 8.2b