---
pubDate: 2021-04-25
title: An Analogy is Like a Bad Argument
tags:
  - writing
abstract: |
  Analogies are easily misused, with great effectiveness, as if they are
  arguments or explanations. Still, analogies can be used well to make a claim
  intuitive after it has been justified.
table_of_contents: false
---

An _analogy_ is a claim that two things, \\(X\\) and \\(Y\\) are 'the same' with
respect to some aspect \\(P\\). As popularly deployed, analogies come in a
variety of styles:

- _metaphor_ – "\\(X\\) is \\(Y\\) (_implicitly:_ with respect to \\(P\\))";
  commonly idiomatic

  - e.g. "the news is music to my ears"
  - e.g. "time is money"
  - e.g. "my memory is foggy"
  - e.g. "the building is a maze"

- _simile_ – "\\(X\\) is like \\(Y\\) (_implicitly:_ with respect to \\(P\\))"
  or "\\(X\\) is as \\(P\\) as \\(Y\\)"

  - e.g. "the desert was like an ocean of sand"
  - e.g. "the empty suitcase is as light as a feather"
  - e.g. "the paper is as white as snow"

- _allegory_ – a story about the \\(P\\) of \\(X\\) that parallels the \\(P\\)
  of \\(Y\\)

  - e.g. the story "Animal Farm" by George Orwell is about the corruption of a
    animal-managed farm that parallels the corruption of communism in the
    Russian Revolution of 1917
  - e.g. [Aesop's fables](https://aesopfables.com), such as the fable of "the
    fox and the grapes" which parallels the propensity to publically deride that
    which one desires but cannot achieve
  - e.g. the Star Trek episode "A Private Little War" which parallels the US
    involvement in the Vietnam War

- _anecdote_ – claim about the \\(P\\) of \\(X\\) as an example of the \\(P\\)
  of \\(Y\\)
  - "Here is an example of a young mother who is worrying about how to secure
    her children's next meal. Poor people in this neighborhood have it hard."
  - "Here is my experience in the field of underwater basket-weaving. You can
    expect to have a similar experience to mine."

Analogy can be a useful way to communicate an intuition about the \\(P\\) of
\\(Y\\) be appealing to an intuition about the \\(P\\) of \\(X\\). As an example
of both analogy's usefulness and of anecdote:

> For teaching about electric current in introductory physics courses, an often
> useful analogy is that between
> [electric current in a circuit and water current in a pipe](http://hyperphysics.phy-astr.gsu.edu/hbase/electric/watcir.html).
> A circuit is like a pipe system, voltage is like pressure, and resistance is
> like pipe diameter. Since the flowing of water in a pipe is immediately
> intuitive, using this analogy allows some of that intuition for electric
> circuits. The difficult, complicated, and unfamiliar behavior of electricity
> in circuits can be roughly reorganized to follow different abstract but
> intuitive rules.

The analogy between electric circuits and water pipes is appealing, especially
before a detailed understanding of the underlying electrodynamics. But an
analogy can only go so far if the analogized things are not identical (in which
case we would have the identity analogy). Electric circuits are like water pipes
in a few high-level respects, but not in the vast majority of other respects.
Why doesn't electricity 'spill out' of a circuit with loose ends?

Overall, the water pipes analogy gives you an intuition about electric current,
but that intuition _didn't actually teach you anything about electric current_
(no matter how much it may _feel_ like you've learned something). Even the
analogical claim that electric circuits are like water pipes in a few particular
respects is not really something about electric circuits themselves, but
extrinsically about the relationship between water pipes and electric circuits.

I think that this observation is very often covertly sidestepped or just
ignored. Analogies so commonly are given as if they were arguments and even
explanations – all the time! Generally, there are two main tactics:

- "The \\(P\\) of \\(X\\) is that because \\(X\\) is like \\(Y\\) (_implicitly:_
  with respect to \\(P\\)) and the \\(P\\) of \\(Y\\) is that"
  - The analogy "\\(X\\) is like \\(Y\\) with respect to \\(P\\)" is used as if
    it were an explanation, but it explains nothing about \\(X\\) itself and
    relies purely on the extrinsic comparison between \\(X\\) and \\(Y\\)
  - e.g. "The Vietnam War is bad because the conflict in Star Trek's 'A Private
    Little War', which critiques the Vietnam War, is bad"
- "\\(X\\) is like \\(Y\\) with respect to \\(Q\\) because \\(X\\) is like
  \\(Y\\) (_implicitly:_ with respect to \\(P\\))."
  - The conclusion sneaks in a new aspect \\(Q\\) that may look superficially
    similar or related to \\(P\\), but is not implied by \\(P\\).
    - e.g. "A country's citizenry is like a big family, so a country should not
      let in anyone who is not like family."
    - e.g. "Computers are just big fancy calculators, so we shouldn't expect a
      computer to every be as intelligent as a human."

TODO: more examples of bad analogical arguments

I've argued that these argument tactics are misuses of analogy, but to be clear
they are only misuses when they are used in place of good arguments. It is so
easy to use analogy in place of arguments because analogies are very persuasive,
satisfying, and by nature intuitive. But analogical arguments have these
attractive qualities regardless of whether they are being used to support a good
or a bad argument.

My warnings given, analogy does have many good uses, including in arguments. I
began with the claim that "Analogy can be a useful way to communicate an
intuition about the \\(P\\) of \\(Y\\) be appealing to an intuition about the
\\(P\\) of \\(X\\)," which is still true even if the analogy doesn't at all
_justify that_ or _explain why_ the \\(P\\) of \\(X\\) and the \\(P\\) of
\\(Y\\) are the same. My ideal use of analogy is to first demonstrate and
explain how the \\(P\\) of \\(X\\) is the same as the \\(P\\) of \\(Y\\), and
then explain how this gives rise to an intuitive analogy between \\(X\\) and
\\(Y\\) with respect to \\(P\\).

Many analogies reflect a deeper truth about a shared nature of \\(X\\) and
\\(Y\\) that accounts for why the \\(P\\) of \\(X\\) is the same as the \\(P\\)
of \\(Y\\). From the observation that electric circuits behave similarly to
water pipes in the mentioned respects, to learn what laws of nature are acting
similarly on these two very different kinds of systems is really to learn
something new about circuits and pipes, as well as learning something more
general about all systems that are acted upon by natural laws in the same way.

This process of _generalization_ is very powerful and the center of what most
people consider the pursuit of interesting knowledge. What makes information
interesting is it's ability to explain many different aspects of a domain in a
concise way. The most interesting mathematical theorems lend insight into a
large range of interesting questions. The most interesting algorithms
demonstrate strategies that abstract over large classes of tasks. The most
interesting literature/film/etc. reflect situations that many people experience
in many different ways.

But what is the difference between analogy and generalization? Well, analogy is
a rhetorical style of generalization – one that seems particularly intuitive to
most people. However, as it is used, analogy is only the _claim_ of
generalization, rather than the process of developing and accounting for the
generalization.

Consider Aesop's fable of "the fox and the grapes". The story is entertaining
and makes sense because, as a human audience, we already have an intuitive
understanding of the sense of spite the fox ends up feeling because it cannot
get the grapes. The story did not instill nor explain that understanding; the
story embodies the claim that the phenomenon is common and natural, and little
else. Perhaps the story highlights an observation that the claim seems to be
true, but even that relies on the fact that the audience can instinctually
derive the claim from the story.

Consider George Orwell's "Animal Farm". The story is not just the analogical
claim that the Russian Revolution's communist ideals (and, perhaps, optimistic
communist ideals in general) were corrupted. The story gives a step-by-step
account for how, gradually, the populace of well-meaning and optimistic
revolutionaries are taken advantage of leaders who know how to say just what
they want to hear in the right style of language in order to get away with
injustice. The story itself is an abstract explanation for how the analogy
between the animal farm and the revolutionary communists holds – importantly,
the story is not just an assertion that the analogy holds. Reading the story can
provide some understanding of how optimistic revolutionary movements can be
corrupted, which is made intuitive and non-specific by the allegory to a
managable set of characters who's cartoonish actions are abstractions of the
complex situations that occur in real-world revolutions.