Critical thinking is the systematic evaluation or formulation of beliefs, or statements, by rational standards. It is systematic because it involves distinct procedures and methods. It entails evaluation and formulation because it is used to both assess existing beliefs (yours or someone else's) and devise new ones. It operates according to reasonable standards in that beliefs are judged according to the reasons and reasoning that support them.
Critical thinking matters because our lives are defined by our actions and choices, and our actions and choices are guided by our thinking. It helps guide us toward beliefs that are worthy of acceptance, that can help us be successful in life, however we define success.
Critical thinking empowers learning and exploring; defense against error, manipulation, and prejudice; and self-discovery.
A consequence of not thinking critically is a loss of personal freedom. If you passively accept beliefs that have been handed to you by your family and your culture, then those beliefs are not really yours. If they are not really yours, and you let them guide your choices and actions, then they—not you—are in charge of your life. Your beliefs are yours only if you critically examine them for yourself to see if they are supported by good reasons.
Some people believe that critical thinking will make them cynical, emotionally cold, and creatively constrained. But there is no good reason to believe that this is the case. Critical thinking does not necessarily lead to cynicism. It can complement our feelings by helping us sort them out. And it doesn't limit creativity—it helps perfect it.
Critical thinking is a rational, systematic process that we apply to beliefs of all kinds. As we use the term here, belief is just another word for statement, or claim. A statement is an assertion that something is or is not the case. When you're engaged in critical thinking, you are mostly either evaluating a statement or trying to formulate one. In both cases your primary task is to figure out how strongly to believe the statement (based on how likely it is to be true). The strength of your belief will depend on the strength of the reasons in favor of the statement.
In critical thinking, an argument is not a feud but a set of statements—statements supposedly providing reasons for accepting another statement. The statements given in support of another statement are called the premises. The statement that the premises are used to support is called the conclusion. An argument then is a group of statements in which some of them (the premises) are intended to support another of them (the conclusion).
Being able to identify arguments is an important skill on which many other critical thinking skills are based. The task is made easier by indicator words that frequently accompany arguments and signal that a premise or conclusion is present. Premise indicators include for, since, and because. Conclusion indicators include so, therefore, and thus.