Philosphy Epistomology

Metaphysics

Study of what exists in some fundamental sense

Epistemology

Study of knowledge and justification

Logic

The study of good reasoning

Value theory

study of values (morals, aesthetic)

Ethics

The study of how one should act, or how we ought to live ones life

Normativity

the concept of standards, rules, or guidelines that determine what is considered good, bad, right, or wrong, focusing on what "ought to be" rather than what "is"

Inference

The psychological process of coming to believe a conclusion on the basis of some reasons

Argument

A set of reasons (premises), together with a conclusion those premises are intended to support → A person typically makes an arguments to get other people to infer the arguments conclusion from its premises 

Proposition

The meaning or content of a declarative sentence, something that can have a truth-value (true or false).

Premise

A proposition that serves as a reason for accepting another proposition (the conclusion).

Conclusion

The proposition that an argument seeks to establish, supported by its premises.

Truth and Falsity 

Truth and falsity are the two possible truth-values (both sentences must be true or false) that a proposition can have.

Logical Circularity

Is when an argument tries to justify its conclusion by relying on that very conclusion (or something equivalent) in its premises.

Deduction

The premises are designed to guarantee the truth of the conclusion without any possibility of error

Validity

• A valid argument is one in which the premises necessarily imply the truth of the conclusion

• Validity Structure: if the premises are true, then the conclusion would have to be true

  • If one says no, then the statement is invalid

• The validity of an argument has nothing to do with whether the premises are true

• Ex. The argument is valid if and only if it is absolutely impossible for its premises to be true and the conclusion is false

Counter examples to validity

Examples that shows the invalidity of the argument

• Where the premises are true but the conclusion is false

  • 1. If I am in San Antonio, I’m in Texas

  • 2. I’m in Texas

  ---

  • 3. I’m in San Antonio

    • Counter Example:

      • 1. If I am in San Antonio, I’m in Texas

      • 2. I’m in Texas

      ---

      • 3. I’m in Austin

Soundness

• The argument is valid and each of its premises are true

• If an argument fails to meet both then the statement is unsound

Conditional Proposition

• Has two parts linked in an if-then structure

• Ex. If you are in London you are in England

• A conditional statement says that if one thing (if a certain “condition) is true then the other is true

Antecedent

The part of the conditional proposition between the words “if” and “then”

• What makes the antecedent is the logical role it plays in the proposition as a whole

  • Ex. You’re in England, if you are in London

Consequent

The part that follows the word “then”

Modus Ponens

A form of argument in which the consequent of a conditional claim is denied by inference from the conditional and the denial of its consequent

1. P → Q

2. P

3. Q

Or

1. P

2. P → Q

3. Q

Always Valid

Modus Tollens

A for of argument in which the antecedent of a conditional claim is denied by inference from the conditional and the denial of its consequent

1. If P, then Q

2. Not Q

3. So not P

Always Valid

Induction

The kind of reasoning where we make and inference from a claim about a sample (the premise) to a claim about a whole domain (the conclusion)

• An inductive argument draws a conclusion about a whole domain on the basis of a sample from that domain.

What makes a strong Inductive Argument

• Stronger with a larger sample size AND

• more representativeness

Abduction

Make an inference from some information (the premises) to an explanation of that information 

What makes strong abductive argument

1. The greater the range of hypotheses considered, the stronger the inference

2. The more false implications a hypothesis has, the weaker the inference

3. The more true implications a hypothesis has that would likely be false if the hypothesis were false, the stronger the inference

4. Given two hypotheses of equal explanatory power, we should prefer the simpler hypothesis

A Posteriori

A claim is a posteriori iff it would be properly justified, at least in some part, through sensory experience

Ex. Is snow white

A Priori

A proposition is a priori iff it would be properly justified (though perhaps not learned)

Ex. 2+2=4

Affirming the Consequent

Even if the premises are true, the conclusion can still be false

• Ex.

  • 1. Whenever you’re in London, you’re in England

  • 2. You’re in London

  • 3. So, you’re in London

• 1. If P then Q

• 2. Q

• 3. P

Never Valid (Always Invalid)

Denying the antecedent

The conditional premise says that if the antecedent is true, then the consequent is true; the other premise says that the antecedent is false. But nothing about the consequent follows from these two premises.

• Ex.

  • 1. Whenever you’re in London, you’re in England

  • 2. You’re not in London

  • 3. So you’re not in England

• 1. If P then Q

• 2. Not P

• 3. Not Q

Never Valid (Always Invalid)

The Paradox of External-World Knowledge

1. I know I have a hand

2. I do not know, I am not a brain-in-a-vat

3. If I know I have a hand, then I know I am not a brain-in-a-vat

While we feel certain about the existence of an external reality, our private experiences provide no way to definitively distinguish between that reality and a deceptive simulation

The epistemic-closure principle