In ordinary usage, skepticism or scepticism (Greek: skeptomai, to look about, to consider) refers to

1. an attitude of doubt or a disposition to incredulity either in general or toward a particular object,
2. the doctrine that true knowledge or knowledge in a particular area is uncertain, or
3. the method of suspended judgment, systematic doubt, or criticism that is characteristic of skeptics (Merriam–Webster).

In philosophy, skepticism refers more specifically to any one of several propositions. These include propositions about

1. the limitations of knowledge,
2. a method of obtaining knowledge through systematic doubt and continual testing,
3. the arbitrariness, relativity, or subjectivity of moral values,
4. a method of intellectual caution and suspended judgment,
5. a lack of confidence in positive motives for human conduct or positive outcomes for human enterprises, that is, cynicism and pessimism (Keeton, 1962).

In classical philosophy, skepticism refers to the teachings and the traits of the Skeptikoi, a school of philosophers of whom it was said that they "asserted nothing but only opined" (Liddell and Scott). In this sense, philosophical skepticism, or pyrrhonism, is the philosophical position that one should avoid the postulation of final truths. Turned on itself, skepticism would deny that it is infallibly certain that skepticism is the only basic perspective.