- A brief presentation on Method of Agreement and Method of Difference (2 out of Mill's 5 Canons) - For USTGS 1st semester 2013-14

1. St. Thomas on Critical Thinking
Dr. Florentino T. Timbreza
Presentor:
Sr. Jennifer R. Cuerdo, OP
MA Guidance & Counselling

2. INTRODUCTION
Two basic rules dominate the whole process
of induction :
1. Positive Principle - Whenever a certain
antecedent (condition) is present, a
particular phenomenon always follows or
occurs; thus, the said antecedent is the
cause of the given phenomenon.

3. 2. Negative Principle - Whenever a
phenomenon occurs in the absence of a
certain antecedent, this antecedent
cannot be the cause of the phenomenon
in question.

4. These basic rules were given their classic
formulations and more explicit expressions
by British philosopher, John Stuart Mill,
called Mill’s Methods of Inductive Inference.
The Five “Canons“ are known as:
1. The Method of Agreement
2. The Method of Difference
3. The Joint Method of Agreement &
Difference
4. The Method of Concomitant Variations
5. The Method of Residues

5. DEFINITION OF TERMS
a. Phenomenon - any event, occurrence, happening
or condition in question
b. Cause - anything that has a positive influence in
the occurrence of something
c. Effect – anything that is produced (caused) by
some other being
d. Antecedent – condition or circumstance which
exists before or at the same time with an event or
phenomenon
e. Consequent – circumstance, event or
phenomenon that follows from the concurrence or
conjunction of some antecedents.

6. THE METHOD OF AGREEMENT
“If two or more instances of the
phenomenon under investigation have
only one circumstance in common, the
circumstance in which alone all the
instances agree is the cause or effect of
the given phenomenon.”
- The application of the general rule that
the only unchanging antecedent of a
given phenomenon is probably the
cause.

7. THE METHOD OF AGREEMENT
Determine the instances:
Instance 1
Instance 2
Find-out the circumstances under each instance.
The circumstance which is common to all
instances in which the phenomenon
under question occurs is probably the cause.

8. THE METHOD OF AGREEMENT
For Example:
Pedro, Jose, Juan and Pablo attended a party
and after the meals, all of them developed
indigestion.
- The indigestion is the phenomenon.
- The instances are Pedro, Jose, Juan and
Pablo.
- The circumstances (food eaten) were rice,
pork, fish, vegetable salad.

9. THE METHOD OF AGREEMENT
Instance Rice Pork Fish Vegetabl Indigestion
s
e
???
Salad
Pedro
Yes
Yes
Yes
Yes
Yes
Jose
Yes
No
Yes
Yes
Yes
Juan
Yes
No
Yes
No
Yes
Pablo
No
No
Yes
Yes
Yes
What is the circumstance common to all
instances? The eating of the FISH –
probable cause of indigestion.

10. THE METHOD OF DIFFERENCE
“If an instance in which the phenomenon
under investigation occurs, and in an instance
in which it does not occur, have many
instances in common save one, that one
occurring only in the former, the circumstance
in which alone the two instances differ, is the
effect, or the cause, or an indispensable part of
the cause of the phenomenon.
- The application of the general rule that a thing
cannot be the cause of a phenomenon which
is present when the phenomenon does not
occur.

11. THE METHOD OF DIFFERENCE
Determine the instances:
Instance 1
Instance 2
Find-out the circumstances under each instance.
If you have one instance that leads to a
phenomenon, and another which does not,
and the only difference is the presence of a
single circumstance in the first situation, it is
the cause of the phenomenon.

12. THE METHOD OF DIFFERENCE
For Example:
Maria and Juana attended a luncheon after
which Maria suffered from food poisoning,
but Juana did not.
- The food poisoning is the phenomenon.
- The instances are Maria and Juana
- The circumstances (food eaten) were rice,
vegetable, oyster, pork adobo.

13. THE METHOD OF DIFFERENCE
Instance Rice Pork Oyste Vegetabl
Food
s
Adobo
r
e
Poisoning
?
Maria
Yes
Yes
Yes
Yes
Yes
Juana
Yes
Yes
No
Yes
No
What is the only circumstance that is
different between Maria and Juana? It is
that Juana did not take OYSTER - which is
probably the cause of Maria’s food
poisoning.

14. LIMITATIONS OF MILL’S METHODS
• First, the rules presuppose that we have a list of
candidate causes to consider. But the rules
themselves do not tell us how to come up with
such a list. In reality this would depend on our
knowledge or informed guesses about likely causes
of the effects.
• The other assumption presupposed by these
methods is that among the list of factors under
consideration, only one factor is the unique cause
of the effect. But there is no guarantee that this
assumption always holds. Also, sometimes the
cause might be some complicated combinations of
various factors.