2. 03
o Truth
o Relevance
o Number
o Diversity
o Disanalogy
TABLE OF CONTENTS
o Casual Reasoning
o Mill’s Method
▪ Method of agreement
▪ Method of difference
▪ Joint method
▪ Concomitant variation
method
▪ Method of residues
INTRODUCTION
APPRAISING ANALOGICAL
ARGUMENT METHODS OF INDUCTION
01
o What is analogy?
o Analogical Reasoning
o Argument by Analogy
3. ❖ Analogy is derived from the Greek word
“Analogia”, which means proportionality
❖ An analogy is a comparison between two
objects, or systems of objects,
❖ claims their similarities.
❖ Analogical reasoning is a type of thinking
that relies upon an analogy,
❖ fundamental to human thought and arguably
some non-human animal.
ANALOGICAL
REASONING
WHAT IS
ANALOGY?
INTRODUCTION
4. Argument By Analogy
❖To argue by analogy is to argue that because two things are
similar, what is true of one is also true of the other.
❖For example:
▪A sparrow is very different from a car but they are still similar in
that they can both move.
▪There might be life on Europe because it has an atmosphere that
contains oxygen just like the earth.
An inductive argument is
an argument that is
intended by the arguer
to be strong enough that,
if the premises were to
be true, then it would be
unlikely that the
conclusion is false.
5. APPRAISING ANALOGICAL ARGUMENT
To know whether the analogy is strong or not, there are certain criteria to check
it:
Truth :
❖First of all we need to check that the two objects being compared are indeed
similar in the way assumed.
❖But just drawing the similarities isn’t enough , it should also be true.
❖For example:
▪This novel is supposed to have a similar plot like the other one we have read, so probably it
is also very boring. If the two novels actually have completely different plots, one being an
office romance and the other is a horror story, then the argument is obviously unacceptable.
6. Relevance :
❖Even if two objects are similar , the analogy is only relevant if the premises
support the conclusion.
❖For example:
▪ Suppose two novels are alike in that their covers are both green. Just because
one of them is boring does not mean that the other one is also boring, since the
color of a book's cover is completely irrelevant to its contents.
Number:
❖ If we discover a lot of shared properties between two objects, and they
are all relevant to the conclusion, then the analogical argument is stronger
than when we can only identify one or a few shared properties.
❖ For example:
▪ Suppose we find out that novel X is not just similar to another boring novel Y
with a similar plot. We discover that the two novels are written by the same
author, and that very few of both novels have been sold. Then we can
justifiably be more confident in concluding that X is likely to be boring novel.
7. Diversity
❖ Here the issue is whether the shared properties are of the same kind or of
different.
❖ We show the similarities in different aspects these different aspects of
similarities are going to increase our confidence in the conclusion a lot more.
❖ For example :
▪ Suppose we have two Italian restaurants A and B, and A is very good. We
then find out that restaurant B uses the same olive oil in cooking as A, and buys
meat and vegetables of the same quality from the same supplier. Such
information of course increases the probability that B also serves good food.
But the information we have so far are all of the same kind having to do with
the quality of the raw cooking ingredients. If we are further told that A and B
use the same brand of pasta, this will increase our confidence in B further.
8. Disanalogy
❖ Even if two objects X and Y are similar in lots of relevant respects, we
should also consider whether there are dissimilarities between X and Y
which might cast doubt on the conclusion.
❖ For example:
▪ Returning to the restaurant example, if we find out that restaurant B now
has a new owner who has just hired a team of very bad cooks, we would
think that the food is probably not going to be good anymore despite
being the same as A in many other ways.
9. Casual reasoning
❖ Casual reasoning is the process of identifying causality: the relationship between
a cause and its effect.
❖ On the surface, casual reasoning seems extremely simple. It is the logical practice
of determining the cause of an event.
❖ To do so, one must establish a relationship between two or more events. The most
straightforward cause and effect relationships are the one-to-one relationships
where one event is the direct and sole cause of the other.
❖ More complicated relationships involve the combination of several events leading
to the outcome event.
❖ For example:
▪ Drinking and driving causes traffic accident.
▪ A woman with blue eyes will have daughters with blue eyes.
▪ Violence on TV and in movies causes people to like violence.
10. Mill's Method
❖ John Stuart Mill (1806-1873) was an English philosopher who wrote on a
wide range of topics ranging from language and science to political
philosophy.
❖ The so-called "Mill's methods" are five rules for investigating causes that
he has proposed.
❖ It has been suggested that some of these rules were actually discussed by
the famous Islamic scientist and philosopher Avicenna (980-1037).
11. The Method of Agreement
Where an effect occurs, there is a single prior factor C that is common to all
those cases, then C is the cause of the effect.
Member /
Food taken
Oyster Beef Salad Noodles Fallen ill?
Mum Yes Yes Yes Yes Yes
Dad Yes No No Yes Yes
Sister Yes Yes No No Yes
You Yes No Yes No Yes
12. Method of Difference
Where one situation leads to an effect, and another which does not, and the only
difference is the presence of a single factor in the first situation , you can infer this
factor as the cause of the effect
Example:
Members Sea Food Salad Chicken Noodles Sick
Mr. A Yes Yes Yes Yes Yes
Mr. B Yes Yes Yes Yes Yes
Mr. C Yes Yes Yes Yes Yes
Mr. D Yes Yes Yes No No
13. Joint Method
The joint method is a matter of applying both the method of agreement and the method
of difference, as represented by the diagram above.
Members Sea Food Salad Chicken Noodles Sick
Mr. A Yes Yes Yes Yes Yes
Mr. B Yes Yes No Yes Yes
Mr. C Yes Yes Yes No Yes
Mr. D Yes No No No No
14. Method of Concomitant Variation
❖ It is an empirical relationship in which the magnitude of one
variable varies with the magnitude of a second variable.
❖ It says that if across a range of situations that lead to a certain effect,
we find a certain property of the effect varying with the variation in a
factor common to those situations, then we can infer that factor as the
cause.
15. Method of Residues
❖ According to this method, if we have a range of factors believed to be
the causes of the range of effects, and we have reason to believe that
all the factors, except one factor C are the causes for all the effects
except one, then we should infer that c is the cause of the remaining
effect.
❖ If a variety of causes have been established to produce a variety of
effects, and we have matched up all the effects, except one then the
remaining effect can be attributed to the remaining cause.
