Scientific Methods of Inquiry (2 of 5)

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

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Scientific Methods of Inquiry (2 of 5)

  1. 1. St. Thomas on Critical Thinking Dr. Florentino T. Timbreza Presentor: Sr. Jennifer R. Cuerdo, OP MA Guidance & Counselling
  2. 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. 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. 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. 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. 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. 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. 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. 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. 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. 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. 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. 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. 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.

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