Mentalism can be defined as a specific type of view regarding the nature of the human cognitive system, and more specifically a view which assumes that human cognition is a richly endowed system, which is to a considerable extent determined by innate features, and which is only marginally influenced or determined by contextual factors (in the widest sense of ‘contextual’). To put it in extreme terms, this view entails that ‘everything is and has always been in the mind’. As such, mentalism is one extreme on a scale of views of which strict behaviorism is the other extreme.
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