1. Philosophy of Science
Science is the study of alternative explanations. What is an explanation?

2. Explanation
An explanation is an answer to the question, “Why 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 that given by convention (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 see that if a bachelor is never married then they 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. Do we 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.