PHI1090 exam questions Flashcards
deductive argument
A deductive argument is a form of reasoning where the conclusion follows necessarily from the premises. If the argument is valid, it means that if the premises are true, the conclusion must also be true. For the argument to be sound, it must be valid and the premises must actually be true in reality.
Example:
1. All humans are mortal.
2. Socrates is a human.
3. Therefore, Socrates is mortal.
inductive argument
An inductive argument is a type of reasoning where specific observations or examples are used to form a general conclusion. The conclusion is not guaranteed but is probable based on the evidence provided.
Example:
1. Every swan I’ve seen so far is white.
2. Therefore, all swans are probably white.
abductive argument
An abductive argument is a type of reasoning where the best possible reason is deduced from the available evidence. It does not guarantee the conclusion but aims to find the most likely or plausible answer.
Example:
1. My car won’t start.
2. The best explanation is that the battery is dead.
Tautology
Tautology is a statement that is always true no matter what. When a statement is structured in such a way that it cannot be false, making it logically valid in all possible situations.
Example: “It will either rain today or it won’t rain today.”
Contradiction
Contradiction is a sentence that is always false. When one statement denies the other, making it impossible for both to be true at the same time.
Example: “It is raining and it is not raining at the same time.”
Contingent
Contingent is a statement that is sometimes true and sometimes false depending on real-world events or circumstances. It relies on observation or evidence to determine the truth.
Example: “It is raining in London.” (This can be true or false depending on the weather.)
Paradox
Paradox is a group of sentences that we individually consider to be true, but when taken together, they appear inconsistent or contradictory, making it seem they cannot all be true at the same time.
Example: The Liar Paradox: “This sentence is false.”
A paradox vs a set of propositions that are consistent
A paradox is a group of sentences that seem individually true but are inconsistent when considered together, while a consistent set of propositions consists of statements that can all be true at the same time without contradiction.
Paradox
Example:
The next statement is true.
The previous statement is false.
Consistent Set of Propositions
Example:
The sky is blue.
Water is wet.
These statements do not conflict and can coexist logically.
Modus Ponens (MP)
Form:
1. If P, then Q.
2. P.
3. Therefore, Q.
Example:
If it is raining, then the ground will be wet.
It is raining.
Therefore, the ground will be wet.
Modus Tollens (MT)
Form:
1. If P, then Q.
2. Not Q.
3. Therefore, not P.
Example:
1. If the alarm is set, it will beep when it goes off.
2. The alarm did not beep.
3. Therefore, the alarm is not set.
—-
1. If it is raining, the streets will be wet.
2. The streets are not wet.
3. Therefore, it is not raining.
Disjunctive Syllogism (DS)
Form:
1. Either P or Q.
2. Not P
3. Therefore, Q
Example:
1. Either you left your keys at home or in the car.
2. You did not leave your keys at home.
3. Therefore, you left your keys in the car.
Affirming the Consequent (Formal Fallacy)
Form:
1. If P, then Q.
2. Q is true.
3. Therefore, P is true.
(Invalid reasoning)
Example:
1. If it is raining, the streets will be wet.
2. The streets are wet.
3. Therefore, it is raining.
(Fallacy: The streets might be wet for other reasons, such as a water leak.)
Appeal to Authority (Informal Fallacy)
Definition: Arguing that a claim is true simply because an authority figure or sometimes unqualified supports it.
Example:
“This skincare product must be the best because a world-famous chef approves it.”
(Fallacy: A chef’s expertise in cooking does not qualify them as an authority on skincare products.)
Ad Hominem (Informal Fallacy)
Definition: Attacking the person making an argument rather than addressing the argument itself.
Example:
“Your argument about climate change is invalid because you failed science class in high school.”
(Fallacy: The personal attack is irrelevant to the merit of the argument being made.)
