Critical Thinking

Critical thinking evaluates the validity of propositions. It is the hallmark and the cornerstone of science because science is a community that aims to generate true statements about reality. The goals of science can be achieved only by engaging in an evaluation of statements purporting to be true, weeding out the false ones, and limiting the true ones to their proper contexts. Its centrality to the scientific enterprise can be observed in the privileges accorded to critical thinking in scientific discourse. It usually trumps all other considerations, including tact, when it appears in a venue that considers itself to be scientific.

A proposition is a statement that claims to be true, a statement that claims to be a good guide to reality. Not all statements that sound as if they may be true or false function as propositions, so the first step in critical thinking is often to consider whether a proposition is really being advanced. For example, “I knew this was going to happen” is often an effort to save face or to feel some control over an unfortunate event rather than an assertion of foreknowledge, even though it sounds like one. Conversely, a statement may not sound as if it has a truth element, but on inspection, one may be discovered. “Read Shakespeare” may sometimes be translated as the proposition, “Private events are hard to observe directly, so one way to learn more about humans is to observe public representations of private thoughts as described in context by celebrated writers.” Critical thinking must evaluate statements properly stated as propositions; many disagreements are settled simply by ascertaining what, if anything, is being proposed. In research, it is useful to state hypotheses explicitly and to define the terms of the hypotheses in a way that allows all parties to the conversation to understand exactly what is being claimed.

Critical thinking contextualizes propositions; it helps the thinker consider when a proposition is true or false, not just whether it is true or false. If a proposition is always true, then it is either a tautology or a natural law. A tautology is a statement that is true by definition: “All ermines are white” is a tautology in places where nonwhite ermines are called weasels. A natural law is a proposition that is true in all situations, such as the impossibility of traveling faster than light in a vacuum. The validity of all other propositions depends on the situation. Critical thinking qualifies this validity by specifying the conditions under which they are good guides to reality.

Logic is a method of deriving true statements from other true statements. A fallacy occurs when a false statement is derived from a true statement.

This entry discusses methods for examining propositions and describes the obstacles to critical thinking.