Philosophy of SciencePhilosophy of SciencePsychology is the science of Psychology is the science of

behavior. Science is the study behavior. Science is the study of alternative explanations. of alternative explanations. We need to understand the We need to understand the concept of an explanation.concept of an explanation.

ExplanationExplanation

An explanation is an answer to the An explanation is an answer to the question, “Why did/does that happen?”question, “Why did/does that happen?”

An explanation is also called a “theory.”An explanation is also called a “theory.” It consists of statements from which one It consists of statements from which one

can deduce the phenomena to be can deduce the phenomena to be explained.explained.

It must satisfy several criteria.It must satisfy several criteria.

Criteria for ExplanationCriteria for Explanation

DeductiveDeductive MeaningfulMeaningful PredictivePredictive CausalCausal GeneralGeneral

Before we can understand Before we can understand the Criteria of Explanation, the Criteria of Explanation,

we need to understand we need to understand types of statements.types of statements.

Types of StatementsTypes of Statements

Definitions= statements of Definitions= statements of equivalence in language.equivalence in language.

Logical Statements= Logical Statements= a prioria priori true or true or false, based on logical analysis.false, based on logical analysis.

Empirical= statements whose truth is Empirical= statements whose truth is tested tested a posteriori—a posteriori—i.e., by i.e., by observations of the “real world.”observations of the “real world.”

DefinitionDefinition

A Definition is a statement of A Definition is a statement of equivalence. equivalence.

For example, For example, “ “A Bachelor is defined as a human male A Bachelor is defined as a human male

who has never been married.”who has never been married.” A definition is neither true nor false. A definition is neither true nor false.

However, it would be confusing to use However, it would be confusing to use terms differently from those accepted terms differently from those accepted by convention (e.g., as in dictionary).by convention (e.g., as in dictionary).

Operational DefinitionOperational Definition

An Operational Definition is a definition An Operational Definition is a definition that specifies the operations of that specifies the operations of measurement.measurement.

For example, operational definitions of For example, operational definitions of “male” might be based on external “male” might be based on external genitalia, chromosomes, hormones, genitalia, chromosomes, hormones, internal organs, birth certificate, gender internal organs, birth certificate, gender identity, sexual orientation, clothes, etc.identity, sexual orientation, clothes, etc.

Logical StatementsLogical Statements

A logical statement is one whose truth is tested A logical statement is one whose truth is tested by logical analysis. A logical statement is by logical analysis. A logical statement is a a prioripriori true or true or a prioria priori false. false.

For example, “Some bachelors are married” For example, “Some bachelors are married”

is is a prioria priori false. We do not need to conduct a false. We do not need to conduct a survey of bachelors to know that this survey of bachelors to know that this statement is false. All we need do is realize statement is false. All we need do is realize that if a bachelor is never married then he that if a bachelor is never married then he cannot now be married. It contradicts the cannot now be married. It contradicts the definition.definition.

Logical StatementsLogical Statements

The statement, “All bachelors are The statement, “All bachelors are human” is a priori true, because the human” is a priori true, because the definition of bachelor is that a person is definition of bachelor is that a person is human and male and never married.human and male and never married.

The term for “and” is conjunction. The The term for “and” is conjunction. The symbol used in set theory is symbol used in set theory is . We can . We can write, write,

bachelor bachelor {human {human male male never never married}married}

Logical StatementsLogical Statements

““Some Bachelors are Married”Some Bachelors are Married” This is This is a prioria priori false. We do not need to false. We do not need to

do a survey; It contradicts the definition.do a survey; It contradicts the definition. ““Some Bachelors are female.”Some Bachelors are female.” This is This is a prioria priori false, given the definition. false, given the definition. ““Some Bachelors are human.”Some Bachelors are human.” A A prioripriori true, since all bachelors are true, since all bachelors are

human.human.

Empirical StatementsEmpirical Statements Empirical statements are statements Empirical statements are statements

whose truth is tested a posteriori.whose truth is tested a posteriori. They are statements about the “real They are statements about the “real

world,” about observations we have world,” about observations we have made or can make.made or can make.

For example, “Some bachelors are taller For example, “Some bachelors are taller than 6 feet.”than 6 feet.”

This statement is a posteriori true, This statement is a posteriori true, because we have measured the heights because we have measured the heights of human males who were never married of human males who were never married and found some who were this tall.and found some who were this tall.

Deduction and LogicDeduction and Logic If the conclusion is true, does it follow If the conclusion is true, does it follow

that the premises are true? that the premises are true? NO!NO! Example:Example:

P1: All things made of cyanide are good P1: All things made of cyanide are good to eat.to eat.

P2: Bread is made of cyanide.P2: Bread is made of cyanide. C: Therefore, Bread is good to eat.C: Therefore, Bread is good to eat.

Conclusion is true, but the premises Conclusion is true, but the premises are false. So, a true conclusion does are false. So, a true conclusion does not validate the premises.not validate the premises.

Logic and Set TheoryLogic and Set Theory

Logic and set theory are closely related.Logic and set theory are closely related. ““If A then B” can be rewritten as If A then B” can be rewritten as All As are B (i.e., A is a subset of B).All As are B (i.e., A is a subset of B). A is a subset of BA is a subset of B A implies BA implies B A A B B

These ideas are really the same.These ideas are really the same.

Transitivity of Set InclusionTransitivity of Set Inclusion

If A is a subset of B (A If A is a subset of B (A B) B) And if B is a subset of C (B And if B is a subset of C (B C) C) Then A is a subset of C (i.e., A Then A is a subset of C (i.e., A C). C). That is, if all As are B and all Bs are That is, if all As are B and all Bs are

C, then all As are C.C, then all As are C. Draw the Venn diagram with A Draw the Venn diagram with A

inside B, which is inside C.inside B, which is inside C.

Transitivity of ImplicationTransitivity of Implication

A A B B B B C C Then A Then A C C In other words, if A then B In other words, if A then B And if B then C And if B then C Then if A then C.Then if A then C. These are all the same underlying idea.These are all the same underlying idea.

Meaning of ImplicationMeaning of Implication

All As are B is true if and only ifAll As are B is true if and only if All not Bs are not A.All not Bs are not A.

Put differently, Put differently, A A B B not B not B not A. not A.Or: Or: A implies B if and only ifA implies B if and only if

Not B implies not A.Not B implies not A.Put another way: Put another way:

If A then B If A then B if not B then not A. if not B then not A.

Example logic problemExample logic problem

Conjecture: “All child abusers were Conjecture: “All child abusers were abused themselves as children.”abused themselves as children.”

A Psychologist wants to test this A Psychologist wants to test this conjecture. conjecture.

There are four lists of people, who There are four lists of people, who are known as abusers, victims, non-are known as abusers, victims, non-abusers, and non-victims. abusers, and non-victims.

Types of ArgumentsTypes of Arguments

Induction is an argument from past Induction is an argument from past occurrences to future events. It is based occurrences to future events. It is based on the “principle of induction” which on the “principle of induction” which holds that past and future events are holds that past and future events are connected by the same laws of nature.connected by the same laws of nature.

Deduction is an argument based on Deduction is an argument based on application of logic. A mathematical application of logic. A mathematical proof is an example of deduction.proof is an example of deduction.

GeneralizationsGeneralizations

A generalization is an empirical A generalization is an empirical statement that applies not only to statement that applies not only to instances at hand but to future cases instances at hand but to future cases that have not yet come to pass.that have not yet come to pass.

Generalizations include correlational Generalizations include correlational and causal statements. and causal statements.

Generalizations are made credible by Generalizations are made credible by induction.induction.

InductionInduction

Example of Induction:Example of Induction: If I drop a pencil, it will fall.If I drop a pencil, it will fall.

(this statement applies not only to one (this statement applies not only to one event, but to an infinite number of event, but to an infinite number of possible future events. There is an possible future events. There is an understood domain of generality, such understood domain of generality, such as we are near the earth and there are as we are near the earth and there are no winds or magnetic fields, etc.)no winds or magnetic fields, etc.)

We gather evidence by dropping pencils.We gather evidence by dropping pencils.

Evidence for InductionEvidence for Induction

The evidence consists of many The evidence consists of many repetitions of the same observation.repetitions of the same observation.

AA11BB11

AA22BB22

AA33BB33

AAnnBBnn At some point, At some point, nn, we predict:, we predict: AAnn+1+1BBnn+1+1

Principle of InductionPrinciple of Induction The principle of induction is not obvious to The principle of induction is not obvious to

many people. People who do not believe many people. People who do not believe in induction are called “existentialists.”in induction are called “existentialists.”

Some people argued that the principle is Some people argued that the principle is made true by a God, who sees to it that made true by a God, who sees to it that natural laws do not change.natural laws do not change.

Thus, the writers and philosophers who Thus, the writers and philosophers who decided that the Gods no longer exist, decided that the Gods no longer exist, concluded that induction no longer holds.concluded that induction no longer holds.

But they don’t jump off the 8But they don’t jump off the 8thth floor. floor.

Improper InductionImproper Induction

An old man decided that he would live An old man decided that he would live forever, based on the observation that forever, based on the observation that every night he went to bed alive, he woke every night he went to bed alive, he woke up alive.up alive.

After 1000 nights, his belief that he would After 1000 nights, his belief that he would live forever increased.live forever increased.

After 10,000 nights, his belief was even After 10,000 nights, his belief was even greater.greater.

What is wrong with the argument that he What is wrong with the argument that he will live forever?will live forever?

Based on Induction over nights,The old man thought he would live forever. Day after day, he lived.However, based on people, you think that as he gets older, he is MORE likely to die. Person after person, they all died, so you don’t think he will live forever.So the argument that he will not live forever is also based on induction.This example illustrates that the concept is not a simple one.

DeductionDeduction Deduction is a logical enterprise, and not Deduction is a logical enterprise, and not

susceptible to the vagueness of induction.susceptible to the vagueness of induction. If the premises are true, and the If the premises are true, and the

deduction logical, then the conclusion is deduction logical, then the conclusion is true.true.

Example: Socrates is an Athenians. All Example: Socrates is an Athenians. All Athenians are Greek. Therefore, Socrates Athenians are Greek. Therefore, Socrates

is a Greek.is a Greek.