1. Business Thinking
Some Principles of Logic

2. Business Thinking APEL: Some principles of Logic
Terms a word or combination of words that can stand by itself as the subject or predicate of a proposition
Silence is Golden (Both are terms)

3. Business Thinking APEL: Some principles of Logic
Proposition that which can be affirmed or denied e.g. Silence is Golden
Silence is the subject
Golden is the predicate

4. Business Thinking APEL: Some principles of Logic
Argument is a series of logically related propositions
All men are mortal (Major premise)
Socrates was a man (Minor premise)
 Socrates was mortal (Conclusion)

5. Business Thinking APEL: Some principles of Logic
DEDUCTION (from the general to the particular)
If the premises are true and the argument is valid then the argument must be true
All of the information is contained (at least implicitly) in the premises

6. Business Thinking APEL: Some principles of Logic
INDUCTION (inference of a general condition from a set of observed instances)
If the premises are true then the conclusion is probably but not necessarily true
The conclusion contains information not present, even implicitly, in the premises

7. Business Thinking APEL: Some principles of Logic
TRUTH concerns the factual correctness or otherwise of the premises
VALIDITY
refers to whether the conclusion is correctly drawn (according to the rules of logic) from the premises
Propositions are true or false; arguments are valid or invalid (these terms are not inter-changeable)

8. Business Thinking APEL: Some principles of Logic
Deductive logic is concerned with the construction of rules for the production of valid arguments (and the exposure of invalid ones)
NB an invalid argument might have a true conclusion (making it harder to spot) and a valid argument might have a false conclusion

9. Business Thinking APEL: Some principles of Logic
Valid and true All cats have four legs My pet is a cat
 my pet has four legs
Invalid and true The industrious are prudent Ants are prudent  Ants are industrious

10. Business Thinking APEL: Some principles of Logic
Valid and false All fish are cold-blooded Whales are fish  Whales are cold-blooded
Invalid and false All cats have tails My hamster has a tail  My hamster is a cat

11. Business Thinking APEL: Some principles of Logic
Construct two arguments….
One which is valid but has a false conclusion
One which is invalid but in which all of the prepositions are true

12. Business Thinking APEL: Some principles of Logic
IF-THEN
Affirming the antecedent (VALID) If (and only if) p, then q p  q
Denying the Consequent (VALID) If (and only if) p, then q Not q  not p

13. Business Thinking APEL: Some principles of Logic
IF-THEN
Affirming the consequent (INVALID) If p, then q q  p
Denying the Antecedent (INVALID) If p, then q Not p  not q

14. Business Thinking APEL: Some principles of Logic
IF and IFF
IF is an ambiguous word….
(a) If I pass my exams, I will be a graduate
(b) If I win the pools, I will become rich
In (a) IF means if and only if (sometimes Iogicians call this IFF)
In (b), there are are other ways of becoming rich (e.g. by inheritance)

15. Business Thinking APEL: Some principles of Logic
SOME and ALL
English is imprecise .. When we say All cats are mammals we are really saying…
All cats are (some of the entire category) of mammals

16. Business Thinking APEL: Some principles of Logic
Contradictions…
To deny that All cats are mammals we do not go to the opposite extreme and say No cats are mammals
The existence of one, egg-laying cat is sufficient for us to argue that Not all cats are mammals without going to the opposite extreme of saying No cats are mammals

17. Business Thinking APEL: Some principles of Logic
SYLLOGISMS
Are a triad of connected propositions that have to follow the rules of logic.
When these rules are broken, we have examples of fallacies

18. Business Thinking APEL: Some principles of Logic
Fallacy of the undistributed middle
All followers of Tony Blair love opera
I am a lover of opera
Therefore I am a follower of Tony Blair

19. Business Thinking APEL: Some principles of Logic
Fallacy of the illicit process
Some clever men are eccentric
Smith is not eccentric
Therefore Smith is not a clever man

20. Business Thinking APEL: Some principles of Logic
Fallacy of the Two Middle Terms
Chalk is different from cheese
Cheese is different from butter
Therefore butter is different from chalk

21. Business Thinking APEL: Some principles of Logic
Valid argument form: Reductio ad absurdum
To prove: p
Assume not-p
Deduce a false statement
Conclude that if not-p is false, then
p must be true
Used extensively in mathematics where it is known as indirect proof

22. Business Thinking APEL: Some principles of Logic
Valid argument form: The dilemma
Either p or q
If p, then r
If q, then s
Either r or s

23. Business Thinking APEL: Some principles of Logic
Theological example
There is evil in the world
Either God cannot prevent evil or he does not wish to
If God can’t prevent evil, he is not all-powerful
If God does not want to prevent evil, he is not benevolent
Therefore God is not all powerful or he is not benevolent

24. Business Thinking APEL: Some principles of Logic
Fallacies of Deduction
Affirming the Consequent
If p then q; q;  p
If we play good football, we will win
We have won
Therefore we played good football

25. Business Thinking APEL: Some principles of Logic
Fallacies of Deduction
Denying the antecedent
If p then q; not p;  not q
If Jeffrey Archer testifies, he is innocent
Jeffrey Archer is not willing to testify
 Jeffrey Archer is not innocent

26. Business Thinking APEL: Some principles of Logic
Fallacies of Induction
Insufficient statistics
Every cat I have seen has a tail
 all cats have tails

27. Business Thinking APEL: Some principles of Logic
Fallacies of Induction
Biased statistics
Every time, I wait for a bus there are always buses going in the opposite direction
Therefore there are always more buses going in the opposite direction

28. Business Thinking APEL: Some principles of Logic
Causal fallacies
Post hoc, ergo propter hoc
B was caused by A because B followed A

29. Business Thinking APEL: Some principles of Logic
Causal fallacies
Confusion of cause and effect
Sober students have money
Drunk students have no money
 give drunk students money to make them sober

30. Business Thinking APEL: Some principles of Logic
Causal fallacies
Common cause
When it’s cold, I put on warm clothes
When it’s cold, I catch a cold
 Warm clothes give me a cold

31. Business Thinking APEL: Some principles of Logic
Equivocation
Only man has a sense of humour
No man is a woman
No women have a sense of humour

32. Business Thinking APEL: Some principles of Logic
Petitio Principii (lit. Asking for the Principle
Or ‘Begging the Question’)
Assuming what we should be trying to prove but is this true in this case ?
All true pleasures lead to happiness
All unselfish acts are true pleasures
 all unselfish acts lead to happiness

33. Business Thinking APEL: Some principles of Logic
Exercises (1 of 6)
If the Tories win the next by-election, they will win the general Election
If they lose the by-election, it follows they will not win the General Election

34. Business Thinking APEL: Some principles of Logic
Exercises (2 of 6)
Since no monetarists were Keynesians and Margaret Thatcher was not a Keynesian, then Margaret Thatcher was a monetarist

35. Business Thinking APEL: Some principles of Logic
Exercises (3 of 6)
An increase in the money supply leads to inflation
So the way to cure inflation is to curb the money supply

36. Business Thinking APEL: Some principles of Logic
Exercises (4 of 6)
All BAMBA students work hard
All students who work hard pass their examinations
 All BAMBA students will pass their examinations

37. Business Thinking APEL: Some principles of Logic
Exercises (5 of 6)
BAMBA students who hate logic are intelligent
BAMBA students who hate logic will not fail their exams
As those who are not intelligent fail their exams

38. Business Thinking APEL: Some principles of Logic
Exercises (6 of 6)
Marx’s theories cannot be taken seriously since his prediction that there would be an increasing degree of polarisation and concentration into opposing classes is ridiculous