George Berkeley is widely regarded as the father of modern idealism, known for his theory of immaterialism, which posits that reality is fundamentally composed of ideas and minds.

Idealism asserts that reality is ultimately mental or spiritual in nature, and that the physical world is either a product of our minds or dependent on our minds for its existence.

Berkeley's idealism posits that physical objects are not independent entities but rather ideas that exist in our minds. He famously stated, 'Esse est percipi,' meaning 'to be is to be perceived.'

Critics of idealism argue that it is based on a false dichotomy between mind and matter, that it cannot account for the existence of evil, and that it leads to skepticism and solipsism, the belief that only one's own mind exists.

Immanuel Kant developed the concept of transcendental idealism, which argues that the structure of our minds shapes our experience of reality, and that certain categories and concepts are inherent in our understanding of the world.

Kant's 'thing-in-itself' refers to the ultimate reality that exists independently of our minds and experience. It is unknowable and inaccessible to us, as our minds impose structure and categories on the world we perceive.

Arthur Schopenhauer argued that the world is a representation of our minds, and that the phenomenal world is merely a veil that conceals the true nature of reality, which is the Will.

Critics of Schopenhauer's idealism argue that it is too pessimistic, as it posits that the world is ultimately driven by a blind and irrational Will, leading to suffering and dissatisfaction.

Georg Wilhelm Friedrich Hegel developed the concept of absolute idealism, which posits that reality is a single, unified, and spiritual substance, and that the world is a manifestation of the Absolute Spirit.

Hegel's dialectic is a method of resolving contradictions in our understanding of the world, a process of historical development and progress, and a way of reconciling the finite and the infinite.

F. H. Bradley argued that idealism is the only way to avoid skepticism, as it posits that reality is ultimately mental or spiritual in nature, and that the physical world is dependent on our minds for its existence.

Critics of Bradley's idealism argue that it is too abstract and difficult to understand, and that it fails to provide a clear and coherent account of reality.

William James developed the concept of personal idealism, which posits that reality is composed of individual minds and their experiences, and that there is no objective or shared reality independent of our minds.

Critics of James' personal idealism argue that it is too subjective and individualistic, as it posits that reality is composed of individual minds and their experiences, and that there is no objective or shared reality independent of our minds.

Alfred North Whitehead argued that idealism is the only way to reconcile science and religion, as it posits that reality is ultimately mental or spiritual in nature, and that the physical world is dependent on our minds for its existence.