Critical thinking involves determining the meaning and significance of what is observed or expressed, or, concerning a given inference or argument, determining whether there is adequate justification to accept the conclusion as true. Hence, Fisher & Scriven define critical thinking as "skilled, active, interpretation and evaluation of observations, communications, information, and argumentation."Moore & Parker define it more naturally as the careful, deliberate determination of whether one should accept, reject, or suspend judgment about a claim and the degree of confidence with which one accepts or rejects it.
Critical thinking gives due consideration to the evidence, the context of judgment, the relevant criteria for making the judgment well, the applicable methods or techniques for forming the judgment, and the applicable theoretical constructs for understanding the problem and the question at hand. Critical thinking employs not only logic but broad intellectual criteria such as clarity, credibility, accuracy, precision, relevance, depth, breadth, significance and fairness.
In contemporary usage "critical" has the connotation of expressing disapproval, which is not always true of critical thinking. A critical evaluation of an argument, for example, might conclude that it is valid. Thinking is often casual and informal, whereas critical thinking deliberately evaluates the quality of thinking. In a seminal study on critical thinking and education in 1941, Edward Glaser writes that the ability to think critically involves three things:
- An attitude of being disposed (state of mind regarding something) to consider in a thoughtful way the problems and subjects that come within the range of one's experiences,
- Knowledge of the methods of logical inquiry and reasoning,
- Some skill in applying those methods.