Lecture 3

By Jerome Cooper,2014-07-03 09:56
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Lecture 3

    Lecture 3-4. Moral Reasoning



    1.1 argumentation

     It is a process of philosophical reasoning in which you support your statement of

    conclusion on a certain problem by using other statements.

1.2 Definition of Argument

     An argument is a group of statements in which it is claimed that one (or sometimes more) statement(s) follow from the other statement(s).



The example again

    (1) Spending so much time online and little on his studies will reduce his GPA. (2) A lower GPA reduces the chance for his admission to graduate programs at a good



    (3) He should spend less time online and more on his studies.

(1)All men are mortal.

     (2) Socrates is a man.

     (3) Socrates is mortal.

     An important note: conclusion and premise are relative terms; may function as alternatives

(1)All men are mortal.

     (2) Socrates is a man.

     (3) Socrates is mortal.

(1) Socrates is mortal.

    (2) All mortals will die.

    (3) Socrates will die.

1.3 Evaluating arguments

     how to distinguish between “good” and “bad” arguments?

    Deductive argument:

     Deductive Validity

     deductive: based on reason and logical analysis

     deductive validity-an argument of which inference structure is logically correct.

    If the premises to the argument were true, the conclusion would have to be true.

Some examples

A. (1) The U.S. president is an American.

     (2) Gorge W. Bush is an American.

     (3) Gorge W. Bush is the U.S. president.


     (1) The U.S. president is an American.

     (2) Gorge W. Bush is the U.S. president.

     (3) Gorge W. Bush is an American.

C. (1) 2 is greater than 3.

     (2) 3 is greater than 1.

     (3) 2 is greater than 1.

D. (1) NUPT is in Jiangsu.

     (2) Jiangsu is in Nanjing.

     (3) NUPT is in Nanjing.

    E. (1) Harvard Univ. is in New York.

     (2) New York is world-famous.

     (3) Harvard Univ. is world-famous.

F. (1) All flowers are plants.

     (2) All roses are flowers.

     (3) All roses are plants.

    A summary of deductive validity An argument is valid only when the conclusion follows from the premises. Its validity has

    nothing to do with the truth of the premises or conclusion.

Some Generalized Forms of Validity

(1) If P, then Q.

    (2) P.

    (3) Therefore, Q.

(1) If it is raining, the streets will be getting wet.

     (2) Now it is raining.

     (3) The streets will be getting wet.

(1) If O, then P.

    (2) If P, then Q.

    (3) O.

    (4) Therefore, Q.

    (1) If it is cloudy, then it will be raining. (2) If it will be raining, the streets will get wet.

     (3) Now it is cloudy.

(4) The streets will get wet.

(1)If P, then Q.

    (2)Not Q.

    (3)Therefore, not P.

(1) Birds can fly.

    (2) Humans cannot fly.

    (3) Humans are not birds.

    Deductive soundness

    An argument is (deductively) sound if and only if it is valid and all of its premises are true.

    Only sound argument can guarantee the truth of the conclusion. Two steps for judging deductive soundness of an argument

     first, deductive validity

     Second, the truth of all the premises.

    Inductive Argument

    Deductive vs. inductive argument illustration


    (1) Every mammal has a heart.

    (2) All horses are mammals.

    (3) Therefore, every horse has a heart.


     (1) Every horse that has ever been observed has had a heart.

     (2) Therefore, every horse has a heart

Deductive argument:

     an argument whose premises are claimed to provide conclusive evidence for the truth of its conclusion. Here "claim" is used because some deductive arguments do not meet this

    claim and are called "invalid."

     aims to establish the truth of conclusion with certainty.

inductive argument:

    If all of the premises are true, the conclusion is probably true, but not necessarily true.

     (1) Thomas is a young man.

     (2) Most young men like watching sports game.

     (3) Thomas likes sports game.

The premises cannot establish the truth of the conclusion with certainty.

    Inductive arguments are empirical because they depend on the evidence of observation.

    3 Types of inductive argument

     Enumerative induction (inductive generalizations)

     the standard method of doing empirical work in science; inference about population based

    on sample

     opinion polls in papers

B. Analogical induction (arguments from analogy)

    C. Hypothetical induction (Abduction)the inference to the best explanation

     (1) If it rains, the streets will get wet.

     (2) The streets are wet.

     (3) It was probably raining.

If H, then O.


     Therefore, H is probably true.

How to evaluate inductive arguments

Inductive strength

    When its premises are true, the probability of its conclusion being true is reasonably high, it is


Inductive cogency

     When an inductive argument is based on the best evidence available so that we accept it

    as reasonably true, it is called inductive cogent argument.

    2. Moral Arguments

    2.1 moral vs. non-moral argument

     a moral argument consists of non-moral (factual) claims and at least one moral principle

    (moral statement or judgment) as its premise.

    2.2 Evaluating moral arguments

    Two steps

    A. Deductive validity-logical structure

    B. Soundness-check all of its premises

     (a) non-moral claims

     (b) moral claims

    How to evaluate moral claims or principles

     From the moral point of view= impartial point of view

     impartial means moral claims or principles (value judgments) count everyone’s interests


B. Qualified universal moral principles

     A moral principle must be universal in the sense that it applies to everyone.

    A moral principle is absolute if it does not allow any exceptions of the application. If the principle is not absolute, we have to identify circumstances in which the principle applies.

    This is called qualify a principle.

C. Basic or ultimate moral principles

     Some moral principles are more basic than others.

Ultimate moral principles are principles we cannot justify by appeal to further principles. the

    Golden Rule

    Justifying basic moral principles

     The divine command theory

    (2) The doctrine of self-evident moral duties

     William D. Ross (1877-1971)

    (3) Moral intuition

     (4) Appeal to the Function of Morality

    (5) Appeal to agreement (Social contract theories) Thomas Hobbes (1588-1679)

     Pre-morality: live in a state of nature; in a war of everyone against everyone John Rawls’s (1921-2002) theory of hypothetical social contracts

     rational, self-interested, individual agents would accept behind of the veil of ignorance if

    given the choice.

    3. Thought Experiment

    Reject the conclusion of an argument, also present a counter-example by giving a so-called

    thought experiment

An example

     Chinese room experiment by John Seale

    4. Doing philosophy

    Analyzing arguments of others or giving your own version

     deductive validity; soundness

     Inductive strength; cogent

    Thought experiments

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