Idealism is a philosophical, psychological, and/or spiritual doctrine which highlights the importance of idealized forms of thought and behavior, and emphasizes the power of imagination and ideas over tangible reality The core of idealism is the idea that all forms of reality, both mental and physical, are ultimately derived from an internal, ideal, or spiritual source. In other words, idealism holds that the mind and its ideas play the primary role in shaping and understanding reality.
One of the most famous and influential examples of idealism can be found in Plato's "The Republic," wherein he describes a utopian society in which the perfect order and ideal harmony are maintained by an unseen force, which he named the "Form of the Good." This form represents a transcendent ideal of knowledge and virtue which serves as the basis for all other forms of knowledge. Plato's theory of idealism has had a profound influence on subsequent philosophy and has been adopted by many leading thinkers throughout the ages.
Another example of idealism can be seen in the French philosopher, René Descartes' "Discourse on Method." In this work, Descartes argues that all external reality is ultimately a mental creation, and that our understanding of the world is derived from the internal principles of reason and understanding. Descartes' philosophy has been called "Cartesian dualism," because it holds that the physical world and the world of thought exist independently of one another, and our understanding of the world is derived from an interior source of knowledge and understanding.
Immanuel Kant's "Critique of Pure Reason" is another example of idealism, wherein he postulates that all knowledge is derived from an ideal source of truth and understanding, and that the physical world is secondary to the principles of reason and understanding. Kant's philosophy is instrumental in shaping the modern view of idealism and has had a significant influence on subsequent philosophies, such as existentialism.
John Locke's "Essay Concerning Human Understanding" is another example of idealism, wherein he argues that knowledge is derived from experience and that our understanding of the world is ultimately shaped by our experience. Locke's work has been instrumental in shaping the modern understanding of idealism and has had a profound influence on subsequent philosophies, such as empiricism.
The philosophies of F.W. Schelling and G.W.F. Hegel are also heavily influenced by idealism. Schelling's "Philosophy of Nature" and Hegel's "Phenomenology of Spirit" both emphasize the power of the mind and its ideas in understanding reality. Both of these works demonstrate the importance of idealism in the understanding of the world, and have been extremely influential in shaping modern thought.
In conclusion, idealism is a philosophical and/or spiritual doctrine which highlights the importance of idealized forms of thought and behavior, and stresses the power of imagination and ideas over tangible reality. Examples of idealism can be found in the works of Plato, Descartes, Kant, Locke, Schelling, and Hegel. Each of these thinkers has contributed to the understanding of idealism and how it shapes our understanding of the world, and their works have been instrumental in shaping modern thought.