NOTE: To change the image on this slide, select the picture and delete it. Then click the Pictures icon in the placeholder to insert your own image. REASONING & ARGUMENTS Chapter 1 page 27 ff.

What is an argument?   “An argument is a connected series of statements to establish a definite proposition”  When trying to persuade  USE AN ARGUMENT  Giving reasons to support a conclusion  Parts of an argument:  PREMISES: propositions taken as support or proof  CONCLUSION: the proposition being proven or supported

Consider this example Capital punishment should not be used because wrongly convicted people will be executed by mistake and this is totally unacceptable. (What is the conclusion? What are the supports?) P1If capital punishment is used, then wrongly convicted people will be executed by mistake. P2 The execution of wrongly convicted people is totally unacceptable. CCapital punishment should not be used. (P = premise, C = conclusion)

Conclusion-Indicators & Premise-Indicators Conclusion-indicators  Therefore  Hence  Thus  So  Consequently  It follows that  We may infer that  We may conclude that Premise-indicators  Since  Because  Given that  Assuming that  Inasmuch as  For the reason that

Deductive Arguments  A DEDUCTIVE argument is either valid or invalid  VALID deductive argument  The conclusion is logically entailed in, or necessarily follows from the premises  (the form of the argument “works” the conclusion follows the premises.  THERE IS INFERENCE: the conclusion is CONNECTED to the premises)  LOGICAL ENTAILMENT:  Occurs when the conclusion must be true given that the premises are true.  INVALID deductive argument  An argument is offered as valid, but the conclusion is not logically entailed in the premises.  An argument could have true premises, and yet the conclusion is false  (there is NO INFERENCE: the conclusion is NOT CONNECTED to the premises)

Deductive Reasoning  Begins with a UNIVERSAL rule, truth, or generalize statement.  Leads to a particular/specific instance of the universal rule.  In valid deductive reasoning / arguments, therefore, the conclusions are NECESSARILY, DEFINITELY OR CERTAIN as true.  All men are mortal.  Socrates is a man.  Socrates is mortal.

Inductive Arguments  An argument where the conclusion is PROBABLY true.  (Inductive reasoning proceeds from specific / particular instances to develop a generalization or “universal” rule)  It’s likely more helpful to judge inductive arguments as strong or weak (not valid or invalid)

Inductive Arguments  The basic assumption: present and past observations lead to a general statement, and will continue to follow that pattern in the future.  Notice: since we haven’t observed ALL the possibilities, our “rule” is only PROBABLE  (Consider David Hume…p. 32)

Abductive Arguments  Arguments where the conclusion is a “best guess” that is to be judged to the most plausible explanation among competing alternatives, given that the premises are true.  The term, “abductive” comes from Charles Sanders Pierce (19 th C. American philosopher)

Comparing the Three Deductive If premises true  conclusion true Impossible for all premises to be true & conclusion false Contradictory for premises to be true and conclusion false If conclusion false, at least one of the premises must be false Inductive If premises true  conclusions probably true unlikely that if premises are true, conclusion false conclusion can be false while all premises true Abductive If premises true  conclusion judged a good candidate, among other possibilities, for being true Ockham’s razor the basic assumption conclusion can be false while premises true

Reasoning & Bias  Francis Bacon ( )  Focused on the utility of scientific knowledge for enabling us to know better  Novum Organon (New Instrument) departure from Aristotle’s Organon  Bacon: emphasized observation and induction  Aristotle: preferred deduction, knowledge for its own sake (not utility)

Idols of the Mind  We strive to be impartial, objective & open-minded  But, we can be swayed from reasoning clearly & correctly by distortions  Bacon called these distortions IDOLS, i.e., “revered false appearances”  Idols of:  The tribe  The cave  The marketplace  The Theatre

Idols of the Tribe  Biases common to all people that “are inherent in human nature and the very tribe or race of men, for man’s sense is falsely asserted to be the standard of things.”  Human understanding like a false mirror  We should be wary of our sense perception for our senses often deceive us.

Idols of the Cave  “Everyone has a cave or den of his own, which refracts and discolours the light of nature, owing either to his own proper and peculiar nature, or his education…  Individual habits of thought, personal experiences, & our own education, interests  The distortion is peculiar to each individual person

Idols of the Marketplace  Our thoughts are traded by the use of words in a conversational marketplace  The idols of the marketplace: sloppy use of words,  i.e., words that are ill-defined, ambiguous  “the ill and unfit choice of words wonderfully obstructs the understanding.”

Idols of the Theatre  Bacon cautions against blind acceptance of established systems of knowledge,  Like theatrical productions that present mere fiction  We need to critically examine the foundations of our philosophical, scientific, theological systems  Uncritical acceptance of systems of thought: idols of the theatre

Consider these distortions:  Stereotyping other people & cultures  Self-centred thinking, our own interests colour our interpretations  Peer pressure, pressure for social conformity, we have a powerful psychological need to be liked & accepted by others  Confirmation bias, the tendency to accept information that confirms what we already think and disregard information that threatens not to confirm what we already think