Philosophy of Science

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

2. Explanation • An explanation is an answer to the question, “Why did/does that happen?” • An explanation is also called a “theory.” • It consists of statements from which one can deduce the phenomena to be explained. • It must satisfy several criteria.

3. Criteria for Explanation • Deductive • Meaningful • Predictive • Causal • General

4. Before we can understand the Criteria of Explanation, we need to understand types of statements.

5. Types of Statements • Definitions= statements of equivalence in language. • Logical Statements= a priori true or false, based on logical analysis. • Empirical= statements whose truth is tested a posteriori—i.e., by observations of the “real world.”

6. Definition A Definition is a statement of equivalence. For example, “A Bachelor is defined as a human male who has never been married.” A definition is neither true nor false. However, it would be confusing to use terms differently from those accepted by convention (e.g., as in dictionary).

7. Operational Definition • An Operational Definition is a definition that specifies the operations of measurement. • For example, operational definitions of “male” might be based on external genitalia, chromosomes, hormones, internal organs, birth certificate, gender identity, sexual orientation, clothes, etc.

8. Logical Statements A logical statement is one whose truth is tested by logical analysis. A logical statement is a priori true or a priori false. For example, “Some bachelors are married” is a priori false. We do not need to conduct a survey of bachelors to know that this statement is false. All we need do is realize that if a bachelor is never married then he cannot now be married. It contradicts the definition.

9. Logical Statements • The statement, “All bachelors are human” is a priori true, because the definition of bachelor is that a person is human and male and never married. • The term for “and” is conjunction. The symbol used in set theory is . We can write, bachelor  {human  male  never married}

10. Logical Statements • “Some Bachelors are Married” • This is a priori false. We do not need to do a survey; It contradicts the definition. • “Some Bachelors are female.” • This is a priori false, given the definition. • “Some Bachelors are human.” • A priori true, since all bachelors are human.

11. Empirical Statements • Empirical statements are statements whose truth is tested a posteriori. • They are statements about the “real world,” about observations we have made or can make. • For example, “Some bachelors are taller than 6 feet.” • This statement is a posteriori true, because we have measured the heights of human males who were never married and found some who were this tall.

12. Deduction and Logic • If the conclusion is true, does it follow that the premises are true? NO! • Example: • P1: All things made of cyanide are good to eat. • P2: Bread is made of cyanide. • C: Therefore, Bread is good to eat. • Conclusion is true, but the premises are false. So, a true conclusion does not validate the premises.

13. Logic and Set Theory • Logic and set theory are closely related. • “If A then B” can be rewritten as • All As are B (i.e., A is a subset of B). • A is a subset of B • A implies B • A  B These ideas are really the same.

14. Transitivity of Set Inclusion • If A is a subset of B (A  B) • And if B is a subset of C (B  C) • Then A is a subset of C (i.e., A  C). • That is, if all As are B and all Bs are C, then all As are C. • Draw the Venn diagram with A inside B, which is inside C.

15. Transitivity of Implication • A  B • B  C • Then A  C • In other words, if A then B • And if B then C • Then if A then C. • These are all the same underlying idea.

16. Meaning of Implication • All As are B is true if and only if • All not Bs are not A. • Put differently, A  B  not B  not A. Or: A implies B if and only if Not B implies not A. Put another way: If A then B  if not B then not A.

17. Example logic problem • Conjecture: “All child abusers were abused themselves as children.” • A Psychologist wants to test this conjecture. • There are four lists of people, who are known as abusers, victims, non-abusers, and non-victims.

18. Types of Arguments • Induction is an argument from past occurrences to future events. It is based on the “principle of induction” which holds that past and future events are connected by the same laws of nature. • Deduction is an argument based on application of logic. A mathematical proof is an example of deduction.

19. Generalizations • A generalization is an empirical statement that applies not only to instances at hand but to future cases that have not yet come to pass. • Generalizations include correlational and causal statements. • Generalizations are made credible by induction.

20. Induction • Example of Induction: • If I drop a pencil, it will fall. (this statement applies not only to one event, but to an infinite number of possible future events. There is an understood domain of generality, such as we are near the earth and there are no winds or magnetic fields, etc.) We gather evidence by dropping pencils.

21. Evidence for Induction • The evidence consists of many repetitions of the same observation. • A1B1 • A2B2 • A3B3 • AnBn At some point, n, we predict: • An+1Bn+1

22. Principle of Induction • The principle of induction is not obvious to many people. People who do not believe in induction are called “existentialists.” • Some people argued that the principle is made true by a God, who sees to it that natural laws do not change. • Thus, the writers and philosophers who decided that the Gods no longer exist, concluded that induction no longer holds. • But they don’t jump off the 8th floor.

23. Improper Induction • An old man decided that he would live forever, based on the observation that every night he went to bed alive, he woke up alive. • After 1000 nights, his belief that he would live forever increased. • After 10,000 nights, his belief was even greater. • What is wrong with the argument that he will live forever?

24. 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.

25. Deduction • Deduction is a logical enterprise, and not susceptible to the vagueness of induction. • If the premises are true, and the deduction logical, then the conclusion is true. • Example: Socrates is an Athenians. All Athenians are Greek. Therefore, Socrates is a Greek.