Idealism is philosophical system. In philosophy, idealism is a long-established tradition. The roots of idealism are embedded deep down in history of philosophy, stretched from beginning and extended to present. Idealism can be seen as a system within the field of metaphysics. One might ask why metaphysics and idealism are related. Well because the most prominent and important concept of idealism is that all entities in nature, their existence and properties are nothing but expression of mind. In idealism, the existence of any object in this physical world which is independent of mind, cannot be defined.
Idealism is divided into two major groups, Subjective Idealism and Objective Idealism. Subjective Idealism is one of most important form of idealism. George Berkeley (1685 – 1753) represented classical subjective idealism, according to him, the knowledge a person have is nothing but his/her ability to perceive. This theory states that the existence of objects around us as the combination of sensation and feelings. This theory states that the existent of material objects (like table, glass etc.) is how our mind perceives them. Objective Idealism states that the existence and reality of objects around us is based on perception of a single Mind, there is no reality outside perception of this single Mind. Other forms of idealism are Transcendental Idealism, Absolute Idealism, Actual Idealism and Epistemological Idealism.
Plato is among first philosophers to describe idealism, other most prominent philosophers of idealism are Gottfried Wilhelm Leibniz, Friedrich Hegel, Immanuel Kant, George Berkeley and Josiah Royce. These philosophers are much devoted, each in their own way, to the study of idealism.
Plato and Idealism:
Plato (428-347 B.C.) an ancient Greece philosopher, supported the concept that the world of ideas and thoughts is real and portray absolute truth and the physical world around us isn’t real, it is merely a reflection and shadow of world of ideas and forms. This concept of Platonic Idealism also referred as “platonic Realism”. The concept of platonic Idealism can be descried using examples from geometry. For example, what is a square? A 2D object with four equal sides, all angles of 90 degree and parallel opposite sides. But this idea of square doesn’t exist in physical world. No example of real world is perfect square. Then how our mind has the idea of a perfect square, because this ideas is based in an ideal world. Plato idealism represents objective idealism.
Idealism says that all the reality and its existence is what and how we examine and experience it. When we perceive and observe these forms of reality through our senses, we see that there is a correlation between this world and our mind. All experience that we have is the experience of us speaking to this world and processing the reply of this world to us. Making sense out of this reply using our mind, something that we can understand and accept and thus this experience makes us into a sensible being.