a mental operation in which a proposition is evoked and then either affirmed or denied. Reasoning, on the other hand, is the process of drawing conclusions from premises or evidence. Both judging and reasoning depend on the possession of the relevant concepts, which are acquired in the process of concept formation. In the case of problem solving, thinking aims at reaching a predefined goal by overcoming certain obstacles. Deliberation is an important form of practical thought that consists in formulating possible courses of action and assessing the reasons for and against them. This may lead to a decision by choosing the most favorable option. Both episodic memory and imagination present objects and situations internally, in an attempt to accurately reproduce what was previously experienced or as a free rearrangement, respectively. Unconscious thought is thought that happens without being directly experienced. It is sometimes posited to explain how difficult problems are solved in cases where no conscious thought was employed. Thought is discussed in various academic disciplines. Phenomenology is interested in the experience of thinking. An important question in this field concerns the experiential character of thinking and to what extent this character can be explained in terms of sensory experience. Metaphysics is, among other things, interested in the relation between mind and matter. This concerns the question of how thinking can fit into the material world as described by the natural sciences. Cognitive psychology aims to understand thought as a form of information processing. Developmental psychology, on the other hand, investigates the development of thought from birth to maturity and asks which factors this development depends on. Psychoanalysis emphasizes the role of the unconscious in mental life. Other fields concerned with thought include linguistics, neuroscience, artificial intelligence, biology, and sociology. Various concepts and theories are closely related to the topic of thought. The term "law of thought" refers to three fundamental laws of logic: the law of contradiction, the law of excluded middle, and the principle of identity. Counterfactual thinking involves mental representations of non-actual situations and events in which the thinker tries to assess what would be the case if things had been different. Thought experiments often employ counterfactual thinking in order to illustrate theories or to test their plausibility. Critical thinking is a form of thinking that is reasonable, reflective, and focused on determining what to believe or how to act. Positive thinking involves focusing one's attention on