Number. 2 © CDTL 2000
Critical Thinking
Professor K.P. Mohanan
Deputy Director, CDTL

Critical Thinking

A collection of mental processes leading up to a decision on the merit of a proposal or product, where ‘merit’ could be in terms of truth, usefulness, effectiveness, significance, desirability, and so on.

Components of Critical Thinking

  • Prior knowledge,
  • Access to meanings of words and sentences,
  • A set of mental dispositions,
  • A set of mental abilities, and
  • A set of criteria of evaluation.

Prior Knowledge

For instance, we reject the claim that humans have 15 fingers on each hand on the basis of our prior knowledge of human beings. Many of us may not have sufficient prior knowledge of horses to evaluate the truth of the claim that horses have 24 teeth.


For instance, the claim that the majority of human beings have four fingers on each hand is false if the intended meaning of the word ‘finger’ is ‘any digit on the hand’, but true if it is ‘any digit on the hand excluding the thumb’. The same remark applies to the astronomer’s rejection of the traditional claim that there are nine planets in the Solar system: eliminating Pluto from the set of planets depends on the meaning we ascribe to the word ‘planet’.

Mental Dispositions

  • Intellectual skepticism, i.e. not believing or rejecting anything without carefully considering the evidence for and against it;
  • Willingness to question and demand evidence;
  • A sense of the uncertainty and fallibility of human knowledge; and
  • Openness of mind, i.e. readiness to reject elements of prior ‘knowledge’ on the basis of new evidence and thinking.

Mental Abilities

  • Ability to identify (a) refuting information, (b) supporting information, (c) internal logical contradictions, and (d) flaws in reasoning.
  • Ability to reason, i.e. to make legitimate inferences.
  • Ability to think of alternative interpretations.

Criteria of Evaluation

For instance, the criteria of evaluating theories in the physical sciences include logical consistency, correctness of predictions, simplicity, and generality. Engineering and technology may replace simplicity with cost. Correctness of predictions is irrelevant for literature.


Further Reading

Mohanan, K.P. (1997). ‘How Does Education Paralyze Independent Thinking?: Critical Understanding and Critical Thinking in Science Education’.

Mohanan, K.P. ‘Modes of Justifying Knowledge Claims’.

Pan, D. (1999). ‘Critical Thinking’. The Effective Student: A Guide to Higher Education at NUS (6th ed.). Singapore: Centre for Development Of Teaching & Learning, National University of Singapore, 77–79.


Back to Top