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Lecture

philosophy lecture 3


Department
Philosophy
Course Code
PHIL 1F94
Professor
Brian Lightbody

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We now come to the 4th component of philosophical methodology which ahs to do with the evaluation
of arguments
As we already know, philosophers first clarify their concepts and definitions. They then set up an
hypothesis to test the concept, finally they construct an argument to support their concept
Philosophical texts puts forward arguments to support their conceptual theories
First we may notice that there are two different meanings for the word "argument" in English. The first
definition would be what Rauhut calls a "verbal disagreement" ( car accident - argument )
A philosophical argument is somewhat different. Every philosophical argument is comprised of a
premise or set of premises and a conclusion. We will define an argument as follows: "An argument is a
series of sentences one of which the conclusions is claimed to be supported by the other premises"
An Example of an Argument
If it rains then the streets will be wet (premises 1)
Therefore: the streets are wet ( conclusion)
The first part of this argument (the if clause) is called the Antecedent. The second part (the then clause)
is called the consequent
The above argument has been put in to standard form - the premises are numbered and the conclusion
is clearly stated
As Rauhut mentions, sometimes it is difficult to put an argument into standard form. But doing so is
absolutely essential in order to clarify the examples
From the Vivekananda: "there is no past or future even in thought because to think it you have to
make it present"
From St. Augustine's De Libero Arbitrio: "see how foolish it is to say: I should prefer non existence to
miserable existence. He who says, I prefer this to that, chooses something. Non existence is not
something, It is nothing. There can be no real choice when what you choose is nothing
Deductive vs. Inductive Argument
The world is structured, ordered and beautiful
Anything that is structured, ordered and beautiful must have been designed by someone to be
Therefore: the world was designed
Example of a deductive argument
The above deductive argument is a valid argument because it has the following
EVALUATING DEDUCTIVE ARGUMENT
VALIDITY AND SOUNDNESS (PG 31-33)
Deductive argument is valid if it satisfies the following condition: "if all premises of the argument are
presumed to be true then the conclusion must be true as well"
All students have rich parents
Peter is a student
Peter has rich parents
Example:
Switch all with some parents - then it would become an invalid argument
It would be invalid because it is possible for the premises to be true and the conclusion false. This is the
very definition of invalidity
VALID VS INVALID ARGUMENT CON'T
Valid argument guarantees that the conclusion must follow it. We assume that the premises are true.
With invalid arguments there is no guarantee that the conclusion is true even if we assume that the
Lecture 3: JUDGING & EVALUATING ARGUMENTS
Tuesday, October 04, 2011
5:20 PM
Philosophy Page 1
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