Analogical Arguments

An analogical argument is an argument that things are alike in a certain respect because they’re alike in other respects

Outline

  1. Analogical Arguments
  2. Examples
    1. Science and Engineering
    2. Law
    3. Business
    4. Probability and Statistics
    5. Ethics
    6. Logic
    7. Metaphysics
  3. Addendum

Analogical Arguments

  • An analogical argument is an argument whose conclusion, that things are alike in a certain respect, is (purportedly) supported by their being alike in other respects.
    • “Support” is used in the sense in which facts and evidence support claims and hypotheses.
    • “Purportedly” allows for bad analogical arguments.

Examples

Science and Engineering

Benjamin Franklin’s Argument that Lightning is Electricity
  • Letter to John Lining from Benjamin Franklin, November 7, 1749
    • “Electrical fluid agrees with lightning in these particulars: 1. Giving light. 2. Color of the light. 3. Crooked direction. 4. Swift motion. 5. Being conducted by metals. 6. Crack or noise in exploding. 7. Subsisting in water or ice. 8. Rending bodies it passes through. 9. Destroying animals. 10. Melting metals. 11. Firing inflammable substances. 12. Sulphureous smell. The electric fluid is attracted by points. We do not know whether this property is in lightning. But since they agree in all the particulars wherein we can already compare them, is it not probable they agree likewise in this? Let the experiment be made.”
  • Argument, Reconstructed
    1. Lightning and sparks are alike in the following respects:
      • 1. Giving light, 2. Color of the light, 3. Crooked direction, 4. Swift motion, 5. Being conducted by metals, 6. Crack or noise in exploding, 7. Subsisting in water or ice, 8. Rending bodies it passes through,  9. Destroying animals, 10. Melting metals, 11. Firing inflammable substances, 12. Sulphureous smell
    2. A spark is electrical in nature
    3. It’s therefore plausible that lightning is electrical in nature.
Physical Model
  1. A small model water turbine has been successfully tested under the same conditions under which full-size turbines are expected to operate. 
  2. Except for size, the model turbine is just like the full-size turbines. 
  3. Therefore, in all probability, the full-size turbines will operate without a problem.

Law

Miranda v. Arizona (Earl Warren)
  1. The Constitution prohibits a person from being compelled to testify against themselves in court.
    • No person “shall be compelled in any criminal case to be a witness against himself.” (Fifth Amendment)
  2. There is no difference, with respect to having a right against self-incrimination, between
    • being compelled to testify against oneself in court
    • being psychologically manipulated to incriminate oneself in a custodial interrogation.
      • A custodial interrogation is the interrogation of a person by law enforcement after they have been taken into custody or otherwise deprived of their freedom in any significant way.
  3. Therefore, the Constitution prohibits a person from being psychologically manipulated to incriminate themselves in a custodial interrogation.

View Miranda v. Arizona

Riggs v. Palmer (1889)
  1. The law prohibits a murderer from receiving the benefit of a life insurance policy whose policyholder they’ve murdered.
    • New York Mutual Life Insurance Co. v. Armstrong (1886)
  2. The following are alike in that they both involve murdering a person in order to obtain a legal claim to a financial benefit provided by the person’s death:
    • murdering a person in order to receive the benefit of a life insurance policy whose policyholder they’ve murdered;
    • murdering a person in order to receive an inheritance from a will whose testator they’ve murdered.
  3. Therefore, the law prohibits a murderer from receiving an inheritance from a will whose testator they’ve murdered.

Business

Comparative Market Analysis
  • A comparative market analysis is used to estimate the sales price of a house based its similarity to nearby, recently sold houses.
  • Argument
    1. Nearby houses comparable to yours recently sold with an average sales price of $250,000.
    2. Therefore, the sales price of your house will be about $250,000.
  • Argument, Reconstructed
    1. The subject house is similar to nearby, recently sold homes in regard to square footage, age, number of bedrooms, number of baths, garage spaces, location, size of lot, general condition, and amenities.
    2. The average sales price of those houses is $250,000.
    3. The sales price of a house depends, more or less, on square footage, age, number of bedrooms, number of baths, garage spaces, location, size of lot, general condition, and amenities.
    4. Therefore the sales price of the subject property will be about $250,000.

Probability and Statistics

Drawing Cards Simultaneously and Consecutively
  1. Randomly drawing five cards simultaneously from a deck of 52 cards, as far as probabilities go, is just like randomly drawing five cards consecutively without replacement.
  2. The probability of getting a flush (i.e. all cards having the same suit) in the latter case is 1/508.
  3. Therefore the probability of getting a flush in the former case is also 1/508.
Statistical Box Model
  1. In the past five years 40 percent of qualified applicants for 100 new entry-level sales positions at the Widget Company have been women but only 20 percent of those hired were women. 
  2. This situation is just like the following box model:
    • A box contains 10 slips of paper, 4 marked W, and 6 marked M. 
    • One hundred slips are selected at random, one at a time, their “gender” recorded, and replaced in the box.
  3. The probability of selecting at most 20 slips marked W is 1/50,000. 
  4. Therefore, the probability that at most 20 women have been hired by chance is likewise 1/50,000.

Ethics

Cheating is Wrong
  1. There’s no morally relevant difference between cheating and surreptitiously changing your grade on the instructor’s spreadsheet.
  2. Changing your grade on the instructor’s spreadsheet is morally wrong.
  3. Therefore, cheating is morally wrong.
Abortion is Wrong
  1. It’s wrong for a person to fire a gun into a closet if they don’t know whether a child is hiding inside. 
  2. Therefore, by analogy, it’s wrong for a person to perform an abortion if they don’t know whether the zygote-embryo-fetus is a human being.
  3. It’s not known at what point a human zygote-embryo-fetus becomes a human being.
  4. Therefore, it’s wrong for a person to perform an abortion.
Abortion is Permissible in the Case of Rape
  • Judith Jarvis Thomson’s Famous Violinist Thought Experiment
    • “You wake up in the morning and find yourself back to back in bed with an unconscious violinist. A famous unconscious violinist. He has been found to have a fatal kidney ailment, and the Society of Music Lovers has canvassed all the available medical records and found that you alone have the right blood type to help. They have therefore kidnapped you, and last night the violinist’s circulatory system was plugged into yours, so that your kidneys can be used to extract poisons from his blood as well as your own. [Unplugging him now would kill him; but in nine months] he will have recovered from his ailment, and can safely be unplugged from you.”
      • “A Defense of Abortion” Philosophy & Public Affairs , 1971
  • Thomson’s Argument
    1. You have no moral obligation to keep the violinist attached, since the situation was forced on you.
    2. Therefore, by analogy, a woman who’s pregnant because of rape has no moral obligation to carry the fetus to term.
  • View Thomson’s Thought Experiment

Logic

Refutation by Logical Analogy
  1. These arguments have the same form:
    • Abortion should be legal because abortions will be performed whether legal or not.
    • Robbery should be legal because robberies will be performed whether legal or not.
  2. The robbery argument is bad.
  3. Therefore the abortion argument is also bad.

Metaphysics

Animal Consciousness (ChatGPT)
  1. Human beings are conscious.
  2. Other mammals have brains, nervous systems, behaviors, and evolutionary histories very similar to the brain, nervous system, behavior, and evolutionary history of homo sapiens.
  3. Therefore other mammals are conscious.
Afterlife (David Hume)
  1. “Where any two objects are so closely connected that all alterations which we have ever seen in the one, are attended with proportionable alterations in the other; we ought to conclude by all rules of analogy, that, when there are still greater alterations produced in the former, and it is totally dissolved, there follows a total dissolution of the latter.”
    • David Hume “On the Immortality of thee Soul”
  2. The mind and body are two such objects.
  3. The body deteriorates, dies, and ceases to function.
  4. Therefore the mind deteriorates, dies, and ceases to function.

Addendum

What’s wrong with this analogical argument?

  1. It’s morally okay to furtively read a newspaper over a stranger’s shoulder (as long as you don’t disturb them).
  2. Piggybacking off a neighbor’s Internet connection is morally analogous to furtively reading over a stranger’s shoulder.
  3. Therefore, it’s morally okay to piggyback off a neighbor’s Internet connection

View Answer