- there is ambiguity in a line of reasoning
- certain statements contradict each other
- a conclusion necessarily follows
- a statement is specific enough
- a statement is actually the application of a certain principle
- an observation statement is reliable
- an inductive conclusion is warranted
- the problem has been identified
- something is an assumption
- a definition is adequate
- a statement made by an alleged authority is acceptable
Ennis defines critical thinking as “determining the authenticity, accuracy, and worth of information or knowledge claims.”
Smith basically thinks that critical thinking is not a skill, but a disposition and requires knowledge of the subject and the authority to think critically, even if that is granted by the person doing the thinking.
“Critical and creative thinking may be viewed academically as unique mental activities, in which individuals can be deficient, but the elements of thinking critically and creatively are in everyone's behavioral and cognitive repertoire. People may often not appear to be thinking critically or creatively because they are often not in situations that permit or call for criticism or creativity, or because they are not disposed to behave critically or creatively in such situations. This does not mean that some individuals are totally incapable of thinking critically or creatively, or that they lack training. It is just that they are not thinking in those ways, for one reason or another.”
He explains further:
“If critical thinking is not a unique set of skills, if it is essentially something that everyone is capable of, that everyone does in some measure all the time, why does critical thinking-or its apparent absence attract such attention? I have a few more remarks to make about specific knowledge, which is at the heart of the ability to be a critical thinker. But there are two other factors to take into account in explaining why some people might not appear to be as critical in their thought as they might be. One of them I have briefly alluded to already, the matter of disposition. The other is more contentious-the extent to which anyone is allowed to be a critical thinker. In other words-how serious all this talk about critical thinking is in the first place.”
The author expands his comments on knowledge:
“Critical thinking does not demand a complex array of learned skills, but competence in whatever you are thinking about. If you understand cooking, you can be critical of the way a meal is prepared. If you are an experienced football fan, you can criticize a football game. If you are a particular kind of engineer, you can criticize the way a bridge or a ship has been built. If you are unable to do any of these things, it will not be because you lack essential critical thinking skills, but because you lack the essential experience. You do not know enough.”
He concludes that critical thinking is a disposition – “a tendency to behave in particular ways on particular occasions.” “Critical thinking is an attitude, a frame of mind.” “…reflective skepticism – the judicious suspension of assent, a readiness to consider alternative explanations, not taking anything for granted when it might be reasonable to doubt.”
“Critical thinking reflects the way we perceive the world; its concern is not with the solution of "problems" but with the recognition of prejudices and biases-including our own. The beginning must be the old Greek adage ‘Know yourself.’"
“Critical thinkers are often not popular. The right to engage in critical thought is not distributed equally, especially in hierarchical, authoritarian, and bureaucratic societies. You could lose your job or your promotion, or your colleagues might find you less agreeable to work with.”
“Critical thinkers are critical; they are argumentative and unsettling; they rock the boat. They can have difficulty treading the line between constructive inquiry and nitpicking trouble-making. They may not always be comfortable to know.”
He closes the chapter with this admonition:
“Critical thinkers must not only reason, they must give reasons; they must not only evaluate arguments, they must argue. They must recognize, and engage in, techniques of persuasion. Effective critical thought is largely a rhetorical exercise. Uncritical passivity in thought and expression go hand in hand.
There is no doubt that the world could do with much more critical thinking. If critical thinking leads to better judgments, fewer problems, and happier consequences, then it is not just children and youth that are in need. It is unlikely that they will become better thinkers by uncritically emulating adults. The development of critical thinking requires a major shift across the generations, and the basis of that shift-if it is not to be catastrophic-must be through language.”
To Think, Frank Smith, Teachers College Press, 1990, 181 pp
Read my summary of To Think at: http://www.scribd.com/doc/163221519/To-Think
 Ennis, Robert H. (1962). A Concept of Critical Thinking, Harvard Educational Review, 32 (1), 82 -83
 Inductive reasoning (as opposed to deductive reasoning) is reasoning in which the premises seek to supply strong evidence for (not absolute proof of) the truth of the conclusion. While the conclusion of a deductive argument is supposed to be certain, the truth of an inductive argument is supposed to be probable, based upon the evidence given. Wikipedia
 The author never mentions the ability to perceive when someone is lying. I think that this needs to be covered specifically and will do so in a separate article.
 Knowledge is a familiarity with someone or something, which can include information, facts, descriptions, or skills acquired through experience or education. It can refer to the theoretical or practical understanding of a subject. It can be implicit (as with practical skill or expertise) or explicit (as with the theoretical understanding of a subject); it can be more or less formal or systematic. In philosophy, the study of knowledge is called epistemology; the philosopher Plato famously defined knowledge as "justified true belief." However, no single agreed upon definition of knowledge exists, though there are numerous theories to explain it. Knowledge acquisition involves complex cognitive processes: perception, communication, association and reasoning; while knowledge is also said to be related to the capacity of acknowledgment in human beings. Wikipedia
 A disposition is a habit, a preparation, a state of readiness, or a tendency to act in a specified way. Wikipedia
 Rhetoric is the art of discourse, an art that aims to improve the capability of writers or speakers that attempt to inform, persuade, or motivate particular audiences in specific situations. As a subject of formal study and a productive civic practice, rhetoric has played a central role in the Western tradition. Its best known definition comes from Aristotle, who considers it a counterpart of both logic and politics, and calls it "the faculty of observing in any given case the available means of persuasion." Rhetorics typically provide heuristics for understanding, discovering, and developing arguments for particular situations, such as Aristotle's three persuasive audience appeals, logos, pathos, and ethos. The five canons of rhetoric, which trace the traditional tasks in designing a persuasive speech, were first codified in classical Rome: invention, arrangement, style, memory, and delivery. Along with grammar and logic (or dialectic), rhetoric is one of the three ancient arts of discourse. From Ancient Greece to the late 19th century, it was a central part of Western education, filling the need to train public speakers and writers to move audiences to action with arguments.