Informal reasoning and fallacies Post hoc ergo propter hoc – after this therefore on account of this If A happens, then B happens then A must cause B Example – GDP increases and globalisation increases – the causal link?? Causal links may be there or somewhere else entirely http://www.experientia.com/blog/uploads/globalisation.jpg

Ad hominem fallacy – against the man Attacking or supporting the person not the argument End poverty – cancel third world debt You are too young and idealistic to understand Einstein was in favour of free milk – so it must be good, focusing on the speaker not the argument

Circular reasoning and begging the question This assuming the truth of what you are meant to be proving. Jesus is the son of God How do you know Because he said he was and the son of God would not lie.

Special pleading – using double standards Making an exception for yourself that you would not find acceptable form another I have to have take time off work because I can’t get a flight back until the day after work starts.

Eqivocation – the same word is used in two different senses in the same argument A hamburger is better than nothing Nothing is better than good health Therefore a hamburger is better than good health http://www.nutrition.natural-remedies-clinic.co.uk/images/food_pyramid.jpg

Argument ad ignorantiam – claiming something is true because it can not be proved to be false http://www.thetoque.com/images/stories/monster_under_bed.jpg

False analogy False analogy when you assume something is similar in one respect it is similar in other too. As time wears away a stone so your broken heart will mend

WHICH IS THE FALSE DILEMMA False dilemma – assuming only two obvious alternatives exist If I can’t have this dress I’ll have nothing to wear for the graduation If you don’t hand this work in you’ll get an E WHICH IS THE FALSE DILEMMA

Now check your understanding of these ideas Loaded question / statements contains a built-in assumption that has not been justified and may be false Do you always cheat in exams? Yes = admitting guilt No = admitting guilt EXPLAIN Well at least he was sober today What does this imply Now check your understanding of these ideas

Causes of bad reasoning Ignorance – may not recognise that a particular form of reasoning is faulty Laziness – we develop fixed habits of thinking and are too lazy to check the argument for supporting evidence Pride – get involved in an argument and we become wrapped up in winning ad not establishing truth Prejudice – we begin with these and manufacture reasons to justify them http://www.thecolumnists.com/johnson/johnson70art1.jpg http://www.epa.state.il.us/environmental-progress/v29/n1/images/littering.jpg

Reason and certainty Fallacies arise in all types of reasoning – can not be relied in to give us knowledge Conclusions of deductive arguments are no more certain than the premises on which they are based However – as a way of thinking, logical reason can not be doubted, this is based on The law of identity – bird is a bird is a bird The law of non contradiction - A is plane so it cannot be not-a-plane The law of the excluded middle everything is either superman or not superman http://www.advancedgrafx.com/images/misc/superman-large.jpg

Doubting reasoning? The doubts that surround deductive reasoning are well…….. Doubting inductive reasoning January Turkeys December Turkey

Here we go – Lateral thinking A problem with reasoning is that we become trapped in the prison of consistency – difficult to admit your wrong To escape the trap we must Lateral thinking is a way of reasoning to do just that De Bono says Traditional thinking digs the same hole deeper Lateral thinking digs a hole somewhere else http://www.tesspowers.com/tesspowers/think_outside_the_box_brain_cp.jpg

You are driving down the road in your car on a wild, stormy night, when you pass by a bus stop and you see three people waiting for the bus An old lady who looks as if she is about to die. An old friend who once saved your life. The perfect partner you have been dreaming about. Knowing that there can only be one passenger in your car, whom would you choose? Go on the internet Find some lateral thinking puzzles and post the best three on your wiki page

linking questions reason

This is what your brain looks like on drugs Language How can vague language lead to bad reasoning? This is what your brain looks like on drugs http://www.sgeier.net/fractals/thumbs/And_this_is_your_Brain_on_Drugs_s.jpg http://www.e-mote.com/images/message/drugs2.jpg

Perception Should we trust reason rather than perception? http://www.aka-paddy.com/projects/happiness.php

Emotion Can emotion be rational?

Can mathematics be reduced to logic? IS IS therefore =

Natural Sciences Is there a logic of scientific discovery? http://www3.shastacollege.edu/dscollon/images/scientific_method.JPG Is there a logic of scientific discovery?

Human Sciences Are human being rational animals? http://www.cartoonstock.com/lowres/mwi0151l.jpg

What kinds of bad reasoning can typically be found in history ? http://newsimg.bbc.co.uk/media/images/39987000/jpg/_39987923_genocide_afpbody.jpg http://www.edinburgh-royalmile.com/history/images/burning-witches.jpg

The Arts What is the relation between creativity and rationality? http://www.bbc.co.uk/history/ancient/egyptians/images/pyramid_gallery_great.jpg What is the relation between creativity and rationality?

Ethics How important is consistency in moral reasoning? http://www1.istockphoto.com/file_thumbview_approve/352492/2/istockphoto_352492_genetic_engineering.jpg http://flatrock.org.nz/topics/intellect_and_entertain/assets/genetic_engineering_run_amok.jpg

Religion Is faith rational or irrational? http://www.cartoonstock.com/newscartoons/cartoonists/rni/lowres/rnin52l.jpg

Truth How important are coherence and consistency for the truth? http://www.mts.net/~hooch/images/flying_pig.jpg