S2 Validity and Soundness (2)

What is a statement?

• A sentence that is true

• A sentence that is false

• A sentence than can be true or false

• An expression of emotion

What is a philosophical argument?

• A series of statements that we know to be true

• A series of statements that tries to demonstrate the truth of a conclusion

• A series of sentences that tries to demonstrate the truth of a conclusion

• Whenever two people disagree about something

What is a valid argument?

• An argument with true premises and a true conclusion

• An argument where we don't know whether the premises are true or false

• An argument where the conclusion could be false even if the premises are true

• An argument where, if the premises are true, the conclusion must true as well

P1: Coffee contains caffeine

P2: Caffeine makes it harder to sleep

C: If you drink coffee it will make it harder for you to sleep

• Invalid

• Valid but unsound

• Valid and sound

P1: If you jump into a lake you will get wet

P2: There are lakes in Scotland

C: If you are wet, you are in Scotland

• Invalid

• Valid but unsound

• Valid and sound

P1: Cristiano Ronaldo is born in Portugal

P2: Portugal is in Europe

C: Cristiano Ronaldo is born in Europe

• Invalid

• Valid but unsound

• Valid and sound

P1: Penguins cannot fly

P2: Penguins are birds

C: Some birds cannot fly

• Invalid

• Valid but unsound

• Valid and sound

P1: All birds can fly

P2: Penguins are birds

C: Penguins can fly

• Invalid

• Valid but unsound

• Valid and sound

P1: Football is a sport

P2: Cristiano Ronaldo plays a sport

C: Cristiano Ronaldo plays football

• Invalid

• Valid but unsound

• Valid and sound

P1: Broccoli is made of chocolate

P2: Chocolate is poisonous

C: Broccoli is made of something poisonous

• Invalid

• Valid but unsound

• Valid and sound