1. Introduction to Philosophy Lecture 1a What is philosophy?
By David Kelsey

2. What is philosophy? The word Philosophy:
Philosophy is the systematic investigation into the foundational concepts and principles of any subject matter.

3. Explaining a subject matter
So philosophy consists of the investigation of any subject matter.
Understanding and Explaining a subject matter
Examples…

4. The disciplines of philosophy
The disciplines of philosophy include:
Philosophy of religion:
Philosophy of mind:
Ethics:
Metaphysics:
Others…

5. The tasks of philosophy
A philosopher investigates the concepts and principles of any subject matter by use of:
Conceptual analysis & Argumentation
Conceptual analysis is the analysis of concepts.
Concepts:
2 definitions: words vs. ideas about a bit of the universe
Examples..

6. The extensions of concepts
Concepts have extensions:
For something to be in the extension of a concept:
the thing must be an instance of the concept.
The thing must fall under the concept
The extension of any concept is defined as all the instances…

7. A view on Concepts
A view on concepts: You might also think that concepts are abstract objects which are instantiated in our world.
The picture:
LOVE KNOWLEDGE STUDENT
PHILOSOPHY SCHOOL
WORD TRUTH GRADE
L W P K T Sc G St
W L P K T Sc St G
L P W K T Sc G St
Above the line: abstract objects
Below the line: our world.

8. Conceptual analysis
If you will remember, one of the main tasks of philosophy is the analysis of concepts.
To analyze a concept is
An explanation
A definition
To define a concept:
Examples in the dictionary
The philosopher’s task:
To provide more detailed, full and clear explanations of concepts you can find in your what?

9. Analytical Definitions: their form
An Analytical definition is composed of a definiendum and a definiens.
The definiendum:
The definiens:
Form: the form of a definition is this:
X =df _____
Which is the definiendum and which is the definiens?
For example,
Bachelor =df unmarried adult male

10. Necessary and Sufficient conditions
We can think of a definition as a set of necessary and sufficient conditions.
X is a necessary condition of Y if and only if (or iff) we cannot have Y without also having X.
Oxygen and Combustion
X is a sufficient condition of Y iff X is all that is needed to get Y.
Being born in the US and citizenship

11. Necessary and Sufficient Conditions
X is both a necessary and sufficient condition of Y iff both
1) we cannot have Y without also having X &
2) X is all that is needed to get Y.
Bachelorhood and being an unmarried adult male

12. Finding correct definitions
For a definition to be adequate the definiendum and definiens must be co-extensive.
For the defiendum and definiens of any definition to be co-extensive it must be the case that:
Everything in the extension of the definiendum is in the extension of the definiens and vice versa…

13. Co-extensiveness: An example
So if your definition of BACHELOR as UNMARRIED ADULT MALE is correct then:
Everything in the extension of BACHELOR is in the extension of UNMARRIED ADULT MALE and vice versa.

14. Testing definitions To determine if a definition is adequate:
determine if its definiendum and definiens are co-extensive.
Is there any item in the extension of one that isn’t in the extension of the other?
Example: Car =df 4 wheeled vehicle one can drive
All Cars are 4 wheeled vehicles one can drive.
All 4 wheeled vehicles one can drive are Cars.
Universal generalizations and counterexamples
A counterexample: a case that violates a universal generalization.

15. Counterexamples Defining Car as 4 wheeled vehicle one can drive:
We need to find either a Car that isn’t a 4 wheeled vehicle one can drive
Or a 4 wheeled vehicle one can drive that isn’t a Car
Thoughts?
Defining Knowledge as true belief:
Finding a counterexample…

16. Counterexamples #2
Say I define Love as a deep seated feeling composed of compassion & care which one can have for another human being.
Can anyone find a counterexample to this definition?
Now let’s try formatting some definitions that aren’t susceptible to counterexamples…