Critical thinking is a rich concept that has been developing throughout the past 2500 years.  The term “critical thinking” has its roots in the mid-late 20th century.  We offer here overlapping definitions, together which form a substantive, transdisciplinary conception of critical thinking.

Critical Thinking as Defined by the National Council for Excellence in Critical Thinking, 1987
A statement by Michael Scriven & Richard Paul for the 

Critical thinking is the intellectually disciplined process of actively and skillfully conceptualizing, applying, analyzing, synthesizing, and/or evaluating information gathered from, or generated by, observation, experience, reflection, reasoning, or communication, as a guide to belief and action. In its exemplary form, it is based on universal intellectual values that transcend subject matter divisions: clarity, accuracy, precision, consistency, relevance, sound evidence, good reasons, depth, breadth, and fairness.

Critical thinking can be seen as having two components: 1) a set of information and belief generating and processing skills, and 2) the habit, based on intellectual commitment, of using those skills to guide behavior. It is thus to be contrasted with: 1) the mere acquisition and retention of information alone, because it involves a particular way in which information is sought and treated; 2) the mere possession of a set of skills, because it involves the continual use of them; and 3) the mere use of those skills (“as an exercise”) without acceptance of their results.