Arguments From Analogy

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Arguments From Analogy
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• The argument from analogy draws a conclusion
  about one thing by comparing it with another. In
  virtue of the similarities, something that is
  true of the one is likely to be true of the
  other.

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• All arguments from analogy involve an analogy.

An analogy is a comparison between 2 or more
things.
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Example from The Tick
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What do they prove?

• Even when analogies are employed in arguments,
  they do not prove anything. No argument from
  analogy can support a proposition with absolute
  certainty. All they can do is show that the
  conclusion is probably true or likely to be true.

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• Arguments from analogy are therefore evaluated as
  weak or strong. Not as true or false, valid or
  invalid, sound or unsound.

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• A weak analogy does not give us much reason to
  think that the conclusion is true.

A strong analogy gives us good reason to think
that the conclusion is probably true.
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Example

• Driving a car is basically just like riding a
  bicycle its all a matter of physical
  coordination and keeping an eye on the road. I
  taught myself how to ride a bicycle, so I should
  be able to teach myself how to drive a car.

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• This does not look like a very good argument, and
  this is because the analogy is not very strong.
  There are some similarities between riding a bike
  and driving a car, but there are also many
  important differences.

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Evaluating Arguments from Analogy

• Strong and Weak Arguments

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• We evaluate the relative strength of arguments
  from analogy in terms of similarities and
  dissimilarities (differences).

These must be relevant ones.
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• The fact that I learned to ride a bike in May and
  am planning to teach myself to drive in January
  is a difference, but an irrelevant one.

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• The fact that you have to steer a bike and a car
  is a relevant similarity, but the fact that cars
  travel much faster than bikes, are bigger, and
  can more easily kill pedestrians are all relevant
  dissimilarities.

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A strong analogy

• Has a large number of relevant similarities and a
  small number of relevant dissimilarities.

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A weak analogy

• Has a small number of relevant similarities and a
  large number of relevant dissimilarities.

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• Because the number of similarities and
  differences is always relative, arguments from
  analogy can only be probably true. They can never
  give us absolutely certain grounds on which to
  accept a conclusion.

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The components of analogical arguments
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1. A Primary Subject

• The thing the conclusion of the argument tells us
  about.

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2. The Analogue

• What the Primary Subject is being compared to.

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3. The Similarities

• The respects in which the Primary Subject and the
  Analogue are being compared, or the features they
  have in common.

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4. The Target Property

• What is said about the Primary Subject in the
  conclusion.

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William Paleys Argument from design for the
existence of God
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• Certain features of a watch lead us to the
  conclusion that it was designed. Its clockwork
  perfection. Its organizational structure. These
  lead you to think it did not come to be by
  accident, but that some intelligent mind must
  have designed it.

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• Since we would conclude from the complexity and
  organization of a watch that the watch was
  designed, we must conclude that the universe was
  also designed.

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The parts of this argument

• The primary subject

The universe

• The analogue

The watch
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• The similarities

The complexities and organization of watches and
features of the universe (seasons, survival
features, homeostasis, ecosystems).

• The Target Property

Being designed
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Evaluating arguments from analogy

• Are there really similarities between the Primary
  Subject and the Analogue?

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Example

• Fishing is like meditating. Hence, fishing is
  very relaxing.

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Paleys argument

• In the case of Paleys argument from design,
  there are identified similarities between the
  Primary Subject (the universe) and the Analogue
  (a watch). They are both complex, highly
  organized, and behave in a regular manner.

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• Are the similarities relevant?

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• This question must always be answered by
  considering what is at issue. The identified
  similarities used to motivate the analogy must be
  ones that reinforce the main point.

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• Are the identified similarities treated
  univocally?

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• In providing an analogy, the identified
  similarities must be understood in the same way,
  within an acceptable range. The arguer should not
  equivocate, or treat features that are really
  quite different as though they were the same.

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Example

• Batman is like abortion. Batman and abortion are
  both complicated. Since abortion is immoral, so
  is Batman.
•  

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Paleys argument

• The use of the words organized, complex,
  regular succession, etc., seem to be used
  univocally, or at least the same within
  acceptable limits. Often this will be a matter of
  judgement and will not be straight-forward.

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• Do the identified similarities outweigh any
  relevant dissimilarities?

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• This is usually the most reliable place to
  examine an analogical argument. Try to identify
  differences between the Analogue and the Primary
  Subject that tend to detract from the idea that
  we can treat them in similar ways.

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Paleys argument

• The sort of complexities and regularities
  identified in the natural world can be adequately
  explained in other ways than by appeal to an
  intelligent designer, whereas the features of a
  watch cannot.

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• The kind of complexity of a watch and of an
  ecosystem is different in a number of ways. The
  watch involves a mechanical complexity of the
  orientation of its parts, whereas an ecosystem
  involves a balance between resources needed for
  species to survive.

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Paleys Argument
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Analogies in Subarguments

• You shouldnt feed squirrels. Squirrels are like
  rats and rats carry disease. Like rats, squirrels
  are rodents that gnaw into your house. They also
  look like rats with puffy tails. Squirrels
  probably carry disease too.

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Fallacies of Analogy

• These are bad arguments that make use of
  comparisons or analogies.

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Fallacy of Two Wrongs

• To argue that because one bad case is permitted,
  similar bad cases should be permitted too.

This is like the suggestion that two wrongs make
a right.
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Example

• People who have tenure dont write half as much
  as sessional instructors and dont put any work
  into teaching. When I get tenure Im going to
  slack off too, stop doing research, and stop
  caring about my classes.

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Example

• The last time I saw Tom he was incredibly rude to
  me. Why should I have to be polite when he isnt?
  If hes at the party this weekend Im going to
  give him a taste of his own medicine.

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Slippery Precedent

• Also called the slippery slope argument.

To argue that although an action may be
acceptable on its own, it will set a precedent
that will lead to other, unacceptable actions.
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The logical version

• If we allow the initial action A (which seems
  permissible), we are logically committed to
  allowing another action B (which is
  impermissible).

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• It is thought that allowing A entails allowing B
  because, although there are differences between A
  and B, there is no relevant conceptual difference
  between A and B.

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Example

• If we allow passive euthanasia, then we will have
  to allow active euthanasia too. There is no
  important conceptual difference between allowing
  someone to die through the cessation of
  treatment, and killing them through active means.
  In either case the intention of the physician is
  the death of the patient, and in either case the
  effect, the death of the patient, is the same.

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The empirical version

• Due to the social forces and beliefs at work in
  the relevant group, allowing A (which is
  permissible) will lead to allowing B (which is
  impermissible).

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Example

• Allowing active euthanasia of the terminally ill
  might be permissible, but it will have disastrous
  effects. The pressures to cut health costs and
  make more resources available could lead
  physicians to administer active euthanasia more
  liberally. Also, the elderly and handicapped
  might feel undue pressure to ask that their lives
  be ended through active intervention.

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• The important thing about an argument like this
  is that it claims B is only likely to follow from
  allowing A, not that it necessarily will. Whether
  or not B will follow A depends on a variety of
  factors, the effects of which are difficult to
  predict accurately. Provided the argument
  acknowledges that it is only probable that the
  bad effects will follow, the argument does not
  commit a fallacy.

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• The logical version of the fallacy occurs if the
  actions in question (A and B) are not logically
  equivalent, but are treated as if they are. If
  letting die and killing are presented as
  logically equivalent, when in fact they are not,
  then the argument would commit the slippery slope
  fallacy.

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• To evaluate logical versions of slippery slope
  arguments, ask if the items under discussion
  really are equivalent. The more relevant
  dissimilarities you can identify between A and B,
  the more likely the argument commits the fallacy.

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• The empirical version occurs if the argument
  simply assumes that the negative consequences
  will result, without offering any justification,
  or if the social factors it appeals to are
  irrelevant to whether or not the unwanted
  consequences are likely to follow.

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Example

• Sure, raising taxes next year will pay for some
  important social programs. But if we let the
  government raise taxes next year, theyll raise
  them again and again in the years to come and
  soon well be paying outrageous taxes.

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Slippery Assimilation

• This occurs when one ignores the fact that many
  small differences that are insignificant on their
  own can, taken together, constitute a significant
  difference.

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Example

• Killing a fetus is just as much an act of murder
  as killing an infant. Theres no real difference
  between a three-month-and-one-day-old fetus, or a
  three-month-and-two-day-old fetus, and so on. So
  where do you draw the line between a three-month
  old fetus and an infant?

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• What the argument neglects is that, while there
  are no individual differences that, from one day
  to the next, mark a significant difference
  between a fetus and an infant, many small changes
  can, taken together over a long period of time,
  constitute a real difference.

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• To evaluate arguments like these, that appeal to
  gray areas, or claim that it is difficult to
  draw the line, ask whether, despite these
  difficulties, clear distinctions can be made.

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Example

• One might not notice the change in hair colour of
  the guy who uses Just For Men hair colouring from
  one day to the next, but that doesnt mean there
  isnt a difference between his having gray hair
  and his having black hair.

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Negative analogy arguments

• These arguments rely on a disanalogy between two
  things. In light of a set of differences between
  the primary subject and the analogue, it is
  argued that there is likely to be a further
  difference.

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The elements of negative analogies

• Primary subject

What the argument is telling us about in the
conclusion.
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• The analogue

What the primary subject is compared to in the
argument.
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• The differences

The ways in which the primary subject and the
analogue are different from each other.
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• The target property

What it is we are saying about the primary
subject in the conclusion (i.e., what further
characteristic it does not possess).
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Example

• Fish are unlike us since they have small brains
  and are not mammals. We feel pain, but it is
  likely that fish do not.

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• In the case of a negative analogy argument, the
  identified differences should be negatively
  relevant to the possession of the target property.

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Example

• My boyfriend is nothing like yours. Yours has
  lied to you throughout your relationship, whereas
  mine has always been honest with me. Furthermore,
  since your boyfriend was a real ladies man and
  mine has always been shy, it is unlikely he has
  cheated on me.

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• Primary subject

The speakers boyfriend.

• Analogue

Your boyfriend.
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• Differences

The speakers has been honest, whereas the
others has not. The speakers is shy whereas
the others is a ladies man.

• Target Property

Not cheating on his partner.
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Some examples

• You shouldnt drink during the day. Once you
  start doing that you will end up being a skid-row
  bum.

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• Revenue Canadas decision that job perks are
  taxable income is a dangerous precedent. Food and
  lodging provided by employers is one thing, but
  now they are going after parking spaces. Soon
  they will be keeping track of how many peanuts we
  have consumed at the office Christmas party.

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• The long-term effects of free trade with the US
  are our concern. Our government will gradually
  lose the ability to interfere in the market place
  for the benefit of Canadians unless the US
  approves. Each time Canada capitulates to US
  pressure it will diminish our independence,
  eventually leading to a complete loss of Canadian
  sovereignty.

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• I can drive after having a couple of beers. Its
  not like I had a couple of scotches. Scotch is a
  hard liquor and beer is not, and the percentage
  of alcohol in beer is much lower than it is in
  scotch.

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• We all agree that discrimination is unacceptable,
  yet people claim that affirmative action is a
  morally defensible policy. This is ridiculous.
  What is affirmative action but a form of
  discrimination?