Transcript Higher / Int. 2 Philosophy

Higher / Int.2 Philosophy 6
Our Learning
Check understanding of Deductive
Validity
Learn about Modus Tollens
Learn about Logical Fallacies
Think about Truth & Soundness
Begin to think about Inductive Force
Higher / Int.2 Philosophy 6
Higher / Int.2 Philosophy 6
Higher / Int.2 Philosophy 6
So what did we learn last lesson?
• a deductive argument is where it is thought that the
premises provide a guarantee of the truth of the conclusion.
• a deductively valid argument is one where the structure
works – where the conclusion logically follows from the
premises.
• one of the two classic forms of deductively valid argument
is Modus Ponens (affirming the antecedent).
Higher / Int.2 Philosophy 6
If it is too hot, then I will sweat
It is too hot
Therefore, I will sweat
The Second Line is agreeing with the first part of the first line
This is AFFIRMING the ANTECEDENT (thing that comes first)
AFFIRMING the ANTECEDENT = MODUS PONENS
Higher / Int.2 Philosophy 6
To the Notes: Modus Tollens
If there is a fire, then there must be smoke
There is no smoke
Therefore, there is no fire
The Second Line is denying the second part of the first line
This is DENYING the CONSEQUENT (the thing that comes after)
DENYING THE CONSEQUENT = MODUS TOLLENS
To the Notes: Logical Fallacies
Higher / Int.2 Philosophy 6
Philosophy
Decide whether the following are MODUS PONENS (affirming) or
MODUS TOLLENS (denying) or whether they are invalid. Also be
ready to say what the conditional premises is.
1. If the sun comes out, it will be a nice day. The sun is out. Therefore it
PONENS
is a niceMODUS
day.
2. If it is wet, then the ground becomes slippery. The ground is not
TOLLENS
slippery.MODUS
So it can’t
be wet.
3. If Mikey continues to misbehave, he will be sent to the Yellow Base.
MODUS TOLLENS
Mikey has
not been sent to the Yellow Base. Therefore Mikey has not
continued to misbehave.
4. If the battery on my Ipod runs out, I will not be able to listen to music.
MODUS
PONENS
The battery
on my
Ipod has run out. So I will not be able to listen to
music.
5. If I am in Cardiff, then I am in Wales. I am not in Cardiff. Therefore I
INVALID
am not in Wales.
Higher / Int.2 Philosophy 6
Summary
MODUS PONENS
Affirming the
Antecedent
(Saying yes to the thing
which comes first)
Valid Deductive
Argument
Affirming the
Consequent
(Saying yes to the thing
which comes after)
Logical Fallacy
Denying the
Antecedent
(Saying no to the thing
which comes first)
Logical Fallacy
MODUS TOLLENS
Denying the
Consequent
(Saying no to the thing
which comes after)
Valid Deductive
Argument
Higher / Int.2 Philosophy 6
… So we know what a valid argument is (one
which works)… but Philosophers are also
interested in TRUTH & SOUNDNESS.
Notes Page 19/20/21
Higher / Int.2 Philosophy 6
Valid = ‘works’ logically follows
Truth = true or false
Sound
SOUND
=
VALID
+
TRUE
Higher / Int.2 Philosophy 6
INDUCTIVE FORCE
PROBABILITY
CERTAINTY
For the last 5 visits to my Granny, I have been offered rich
tea biscuits. I am about to visit my Granny. I will be
offered rich tea biscuits
We had a white Christmas last year – and the year before.
We will have a white Christmas this year.
Higher / Int.2 Philosophy 6
Deductively
Valid
Arguments
Philosophy
INDUCTIVE FORCE
Inductively
Forceful
Arguments
Arguments that are
neither valid nor
Inductively forceful
Higher / Int.2 Philosophy 6
Our Learning
Check understanding of Deductive
Validity
Learn about Modus Tollens
Learn about Logical Fallacies
Think about Truth & Soundness
Begin to think about Inductive Force