Imagination describes the power to form a mental image of something that is not presently perceived by one's senses or has never been experienced in reality. Imagination plays a role in many aspects of culture, as well as in human development. The human experience is composed of sensation and intellect and also of imagination.

Modern philosophers have defined imagination. Emanuel Kant (1724–1804) labeled it a distinct mental faculty through which thought and experience can come together. David Hume (1711–1776) and other empiricist philosophers explained imagination as an associative process, in which ideas, developed through experiences, become united with experience.

Hume viewed imagination as a turbulent and unpredictable force that has to remain within the bounds of reason. He called it a natural structure of the mind that must be trained to appreciate art's beauty. Like Hume, Samuel Johnson thought that imagination must be pruned. He said that writers have a duty to write creatively but prudently. Johnson had a moral vision of art, believing that artists must use their imaginations to inspire audiences toward goodness. His view was utilitarian, valuing art insofar as it can direct people to virtuous behavior.

Kant delineated two uses for imagination. The first is in ordinary thought and perception, and the second is in the aesthetic experience. Kant describes two elements, the sensing of something and the thing itself, as becoming synthesized by an act of the imagination. In ordinary thought, the imagination is bound by one's beliefs, such as the belief that an object lies before that person. In the world of aesthetics, imagination is free from concepts. It can engage in free play, bringing new concepts to bear on an experience that is free from concepts.

Jean-Paul Sartre (1905–1980) also refers to the creative capacity of imagination. In his 1940 book The Imaginary: The Phenomenological Psychology of the Imagination, he describes imagining as not existing. In memory and perception, experiences are considered real. In imagination, content has no reality behind it. Individuals summon this content when they see a picture or listen to a piece of music. Imagination seems to be the extra ingredient in the aesthetic experience that bridges the sensory with the intellectual. Rene Descartes (1596–1650), in contrast, failed to find any clear difference between dreams and waking life.

Imagination was originally viewed as an aberrant function of the mind. Thinkers deemed it subservient to reason and order. Art was simply a replica of something real, rather than an act of creation. Aristotle changed that line of thinking, linking human imagination to the power of art. He deemed the expressions of a poet as potentially occurring. The ascendancy of art opened way to new critiques of art that recognized its merits.

The division between imagination and reason was used by Romantic critics in the 18th century for their own purposes. Percy Shelley (1792–1822) designated the imagination as the ideal form of human expression. Reason, according to Shelley, is subservient to imagination, a tool for implementing one's imagination. Shelley depicted literature as the most basic expression of imagination. Imagination bridges perception and expression.

Samuel Taylor Coleridge (1772–1834) distinguished between the primary and secondary imagination to understand artistic creation. He considers our existence a product of our ability to imagine. Our primary imagination establishes a relationship between ourselves and the world. The secondary imagination is taken hold of by artists, who compose new creations out of existing materials.

Imagination is used in three ways. First, there is a usage that supposes a process in one's mind, such as visualization. That is the imaginary. Then, there is the usage that is equivalent to supposing, such as, "Suppose we had a castle." Last, there is the usage in the phrase "in imagination," such as, "You are a superstar in your imagination." That type of imagination is marked by creative thought. All three describe something unreal. Imagination connotes freedom and spontaneity.

Albert Einstein (1879–1955), the great thinker and mathematician, said, "Imagination is more important than knowledge, as knowledge is limited, but imagination can encircle the world."

Selected full-text books and articles on this topic

E. J. Furlong.
George Allen & Unwin, 1961
Imagining: A Phenomenological Study
Edward S. Casey.
Indiana University Press, 1976
The Imaginary: A Phenomenological Psychology of the Imagination
Jean-Paul Sartre.
Routledge, 2003
Imagination, Philosophy, and the Arts
Matthew Kieran; Dominic Mciver Lopes.
Routledge, 2003
Stretching the Imagination: Representation and Transformation in Mental Imagery
Cesare Cornoldi; Robert H. Logie; Maria A. Brandimonte; Geir Kaufmann; Daniel Resiberg.
Oxford University Press, 1996
Imagination and the Nature of Choice
G. L. S. Shackle.
Edinburgh University Press, 1979
Imaginary Companions and the Children Who Create Them
Marjorie Taylor.
Oxford University Press, 1999
Child's Play: Myth, Mimesis and Make-Believe
L. R. Goldman.
Berg Publishers, 1998
Tradition and Imagination: Revelation and Change
David Brown.
Oxford University Press, 1999
The Fantasy Principle: Psychoanalysis of the Imagination
Michael Vannoy Adams.
Brunner-Routledge, 2004
The Poetics of the Mind's Eye: Literature and the Psychology of Imagination
Christopher Collins.
University of Pennsylvania Press, 1991
The Use of Imagination: Educational Thought and the Literary Mind
William Walsh.
Chatto & Windus, 1960
The Moral Imagination and Public Life: Raising the Ethical Question
Thomas E. McCollough.
Chatham House Publishers, 1991
Religious Imagination
James P. Mackey.
Edinburgh University Press, 1986
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