Critical thinking

This is a passage from the management bestseller In Search of Excellence by Peters and Waterman:

@If you place in a bottle half a dozen bees and the same number of flies, and lay the bottle horizontally, with its base (the closed end) to the window, you will find that the bees will persist, till they die of exhaustion or hunger, in their endeavour to discover an opening through the glass; while the flies, in less than two minutes, will all have sallied forth through the neck on the opposite side. … It is the bees’ love of flight, it is their very intelligence, that is their undoing in this experiment. They evidently imagine that the issue from every prison must be where the light shines clearest; and they act in accordance, and persist in too-logical action. To bees glass is a supernatural mystery. … And, the greater their intelligence, the more inadmissable, more incomprehensible, will the strange obstacle appear. Whereas the featherbrained flies, careless of logic … flutter wildly hither and thither, and meeting here the good fortune that often waits on the simple … Necessarily end up by discovering the friendly opening that restores their liberty to them (Peters and Waterman, 1988, p. 108).@

Some people think that the example in the passage shows that logical thinking is a bad thing. Do you think the example succeeds in establishing such a conclusion? Why or why not?

In Alec Fisher's book Critical Thinking, he quotes Robert Ennis's definition of critical thinking:

@Critical thinking is reasonable, reflective thinking that is focused on deciding what to believe or do.@

In our course, we define critical thinking as "clear and rational thinking". Note that "reflective thinking" is not mentioned. Do you think this is an important defect with our definition?

Clarify, summarize, and organize

Literal meaning

For each set of statements below, determine whether they have the same truth-conditions. In other words, determine whether there is any situation where one of them is true and the others are false.

  • Everybody is innocent until proven guilty.
    Nobody is guilty until proven to be not innocent.
  • You must not sign the document.
    It is not the case that you must sign the document.
  • There are many restaurants in Paris, and Maxim is the best.
    No restaurant in Paris is better than Maxim.
  • Do not say anything in case the ICAC is present.
    Do not say anything if the ICAC is present.
  • We do not add preservatives to our food.
    Our food contains no preservatives.
  • If any of the o-rings is broken, the space shuttle will explode.
    If every o-ring is broken, the space shuttle will explode.
  • I shall incorporate your suggestions.
    I shall try to incorporate your suggestions.
    I shall try to incorporate your suggestions where possible.
  • We are going to invite interesting parties to apply to the scholarship.
    We are going to invite interested parties to apply to the scholarship.

Consider the first statement below, and discuss whether the other statements have the same meaning or not.

  • The County sent an inspector who made observations as to the condition of the sidewalk and concluded that it was uneven.
  • The County inspector observed the sidewalk and concluded that it was uneven.
  • The inspector sent by the County to observe the sidewalk concluded that it was uneven.
  • The County sent someone to inspect the sidewalk, and that person concluded that it was uneven.

In the Dec 2005 Legal System exam of the HKU Law Department, there was an essay question where students are supposed to point out that it is not correct for the judge to tell the jury to ignore X. But many students wrote down the following statements instead:

  • Judge should tell jury to ignore X;
  • Jury should not ignore X;
  • Judge should not tell jury whether to consider X;
  • It is not the judge's right to direct the jury on the effect of X;
  • Judge should not control the jury.

See if you can explain why all these students have marks deducted from their paper.


List all the possible interpretations for these sentences.

  • Put the book on the table by the window in the bedroom.
  • The policemen were told to stop drinking at midnight.

  • The American philosopher William James told the story of a group of hunters in the forest. One of the men sees a squirrel on a tree, and the squirrel sees him. The squirrel scrambles to the opposite side of the tree from the man. The man circles the tree, and the squirrel cautiously stays on the opposite side of the tree from him. The man runs around the tree in circles trying to look at the squirrel, but the squirrel always remain on the opposite side. Now the quesiton is, did the man go around the squirrel or not? Some of the hunters said yes, and some said no. What do you think? How would you resolve this dispute?

Determine whether these statements are ambiguous. If ambiguity is present, which type is it?

  • New chief vows to avoid drastic changes while reviewing much-criticised reforms. [SCMP caption 28 June 2002]
  • I include with this email my legal advice to the company which has been praised by many people.
  • The analysis of the nimo computer virus that has been circulating on the internet has now arrived.
  • I wrote a poem once about a great encounter I had with a dear early in the morning that was very moving. [US Presidential candidate John Kerry New York Times March 7th 2004.]
  • For sale - ten puppies from an Australian terrier and a Boston terrier.
  • This regulation governs disaster assistance for services to prevent hardship caused by fire, flood, or acts of nature that are not provided by the Red Cross.


  • Write a few paragraphs on different topics using the "general/particular/implication" format.


Apply the method of genus and differentia to give definitions for these terms the best you can. For each definition, identify the part that corresponds to "genus" and the part that corresponds to "differentia".

  • air-conditioner
  • piano concerto
  • gambling
  • coward

Evaluate these definitions and see if they have any problems.

  • X leads a meaningful life = X leads a life pursuing aims that are recognizied to be important by the members of X's community.
  • Marriage is the grave of romantic love.
  • A diamond is a transparent precious stone of pure carbon in crystallized form, the hardest substance on earth.
  • A brave man is one who does not run away from danger.
  • A cloud is a large semi-transparent mass with fleecy texture suspended in the atmosphere whose shape is subject to continual and kaleidoscopic change.
  • Poetry is the most beautiful, impressive, and widely effective mode of saying things.
  • Truth = what you can defend against all criticisms.
  • Hatred = the wish to harm others or to ruin something that belongs to or is dear to others.

The MBA program of University X has a web site that provides general information, course web sites, and analysis reports that require payment to download. The web designer wants to use a script (program) on the web site, but she is not sure whether she is allowed to use to program under its license. Read the following license and give her some advice.


(A) You may use the script on non-commercial websites subject to this license. For the purpose of this license "non-commercial websites" are defined as:

  1. personal or hobby sites which generate no revenue;
  2. websites owned and maintained by a charitable or not-for-profit organisation; this includes websites of registered charities where the principal activity is fundraising;
  3. school, college or other educational websites;

(B) You may not use the script on commercial websites. For the purpose of this license "commercial websites" are defined as:

  1. any site which is built, owned or maintained by a profit-making person or organisation;
  2. any site which generates revenue, even if it's otherwise non-commercial;
  3. government, government-agency or political-party websites;

A definition game

Divide the students into two groups. One group identifies an object in the room (e.g. chair, mobile phone) and asks the other group to provide a definition. The first group is responsible for criticizing the definition and the second group will continue to modify the definition to deal with objections from the first group.

Necessary and sufficient conditions

Are these statements true or false? Explain why.

  • If A is an example of B, then being A is sufficient for being B.
  • If A is a necessary condition for C, and B is a sufficient condition for C, then "satisfying both conditions A and B" would be a condition that is both necessary and sufficient for C.
  • If touching a person X is not necessary for assaulting X, then assualting X is not sufficient for touching X.