German idealism

According to Immanuel Kant, the human mind is not capable of directly experiencing the external world as it is in itself. Instead, our experience of the world is mediated by the a priori categories and concepts that are inherent in the human mind. These categories and concepts, which Kant calls "transcendental" because they are necessary for any experience, structure and organize our experience of the world, but they do not provide us with direct access to the thing-in-itself, which is the ultimate reality.

Kant's transcendental idealism has two main components. The first is the idea that the human mind is not a passive recipient of sensory information, but is actively involved in shaping our experience of the world. The second is the idea that the nature of reality is ultimately unknowable to us, because our experience of the world is mediated by the structures of our own minds.

Kant restricted the domain of knowledge to objects of possible experience. His three most notable successors, however, would react against such stringent limits.[5]

In 1787, Friedrich Heinrich Jacobi addressed, in his book On Faith, or Idealism and Realism, Kant's concept of "thing-in-itself". Jacobi agreed that the objective thing-in-itself cannot be directly known. However, he stated, it must be taken on belief. A subject must believe that there is a real object in the external world that is related to its subjective representation. This belief is a result of revelation or immediately known, but logically unproved, truth. The real existence of a thing-in-itself is revealed or disclosed to the observing subject. In this way, the subject directly knows the ideal, subjective representations that appear in the mind, and strongly believes in the real, objective thing-in-itself that exists outside the mind. By presenting the external world as an object of belief, Jacobi aimed to legitimize belief – or faith – in general.

Karl Leonhard Reinhold published two volumes of Letters Concerning the Kantian Philosophy in 1790 and 1792. He tried to prove Kant's assertion that humans and other animals can know only phenomena, never things-in-themselves. In order to establish his proof, Reinhold stated an axiom that could not possibly be doubted. From this axiom, all knowledge of consciousness could be deduced. His axiom was: "Representation is distinguished in consciousness by the subject from the subject and object, and is referred to both."

He thereby started, not from definitions, but, from a principle that referred to representations in a conscious mind. In this way, he analyzed knowledge into (1) the knowing subject, or observer, (2) the known object, and (3) the image or representation in the subject's mind.

Gottlob Ernst Schulze objected to Kant's critical philosophy as self-contradictory. According to Kant himself, the law of cause and effect only applies to the phenomena, not between phenomena and things-in-themselves. Yet, Kant directly claims that the thing-in-itself is the cause of phenomena.

After Schulze had seriously criticized the notion of a thing-in-itself, Johann Gottlieb Fichte produced a philosophy similar to Kant's, but without a thing-in-itself. Fichte asserted that our representations are the productions of the "transcendental ego", that is, the knowing subject. For him, there is no external thing-in-itself. On the contrary, the subject is the source of the external thing, object, or non-ego.

Fichte claimed that this truth was apparent by means of intellectual intuition. That is, the truth can be immediately seen by the use of reason.

Friedrich Wilhelm Joseph Schelling (1775–1854) claimed that the Fichte's "I" needs the Not-I, because there is no subject without object, and vice versa. So subjective representations are identical to the extended objects which are external to the mind. According to Schelling's "absolute identity" or "indifferentism", there is no difference between the subjective and the objective, that is, the ideal and the real.

Friedrich Schleiermacher was a theologian who asserted that the ideal and the real are united in God. He understood the ideal as the subjective mental activities of thought, intellect, and reason. The real was, for him, the objective area of nature and physical being. Schleiermacher declared that the unity of the ideal and the real is manifested in God. The two divisions do not have a productive or causal effect on each other. Rather, they are both equally existent in the absolute transcendental entity which is God.

Salomon Maimon influenced German idealism by criticizing Kant's dichotomies, claiming that Kant did not explain how opposites such as sensibility and understanding could relate to each other. As he clearly saw, this presented a serious skeptical objection to the Kantian project:

By thus pointing out these problematic dualisms, Maimon and the neo-Humean critics left a foothold open for skepticism within the framework of Kant’s own philosophy. For now the question arose how two such heterogeneous realms as the intellectual and the sensible could be known to correspond with one another. The problem was no longer how we know that our representations correspond with things in themselves but how we know that a priori concepts apply to a posteriori intuitions.[6]

Maimon attempted to resolve this problem by introducing the concept of "infinite mind". For this reason, Maimon can be said to have returned to pre-Kantian transcendent speculation. In the words of Frederick C. Beiser, "by reviving metaphysical ideas from within the problematic of the critical philosophy, he gave them a new legitimacy and opened up the possibility for a critical resurrection of metaphysics.[7]

Georg Wilhelm Friedrich Hegel responded to Kant's philosophy by suggesting that the unsolvable contradictions given by Kant in his Antinomies of Pure Reason applied more broadly to reality as such. Given that abstract thought is thus limited, he went on to consider how historical formations give rise to different philosophies and ways of thinking. In The Phenomenology of Spirit, he went on to trace formations of self-consciousness through history and the importance of other people in the awakening of self-consciousness. Thus Hegel introduced two important ideas to metaphysics and philosophy: the integral importance of history and intersubjectivity.

Hegel also claims to sublate the traditional concept of God with his concept of absolute spirit. Spinoza, who changed the anthropomorphic concept of God into that of an underlying substance, was praised by Hegel whose concept of absolute knowing fulfilled a similar function. Hegel claimed that "You are either a Spinozist or not a philosopher at all".[8]

Neo-Kantianism emphasizes the critical dimension of Kant's philosophy as against the perceived excesses of German Idealism. It was the dominant philosophy in Germany during the late 19th and early 20th centuries. Although there was considerable disagreement among the neo-Kantians themselves, they shared a commitment to some version of the "transcendental method".[9]

In England, during the nineteenth century, philosopher Thomas Hill Green embraced German Idealism in order to support Christian monotheism as a basis for morality. His philosophy attempted to account for an eternal consciousness or mind that was similar to Berkeley's concept of God. John Rodman, in the introduction to his book on Thomas Hill Green's political theory, wrote: "Green is best seen as an exponent of German idealism as an answer to the dilemma posed by the discrediting of Christianity…."[10]

"German idealism was initially introduced to the broader community of American literati through a Vermont intellectual, James Marsh. Studying theology with Moses Stuart at Andover Seminary in the early 1820s, Marsh sought a Christian theology that would 'keep alive the heart in the head.' "[11] Some American theologians and churchmen found value in German Idealism's theological concept of the infinite Absolute Ideal or Geist [Spirit]. It provided a religious alternative to the traditional Christian concept of the Deity.[12] The Absolute Ideal Weltgeist [World Spirit] was invoked by American ministers as they "turned to German idealism in the hope of finding comfort against English positivism and empiricism."[13] German idealism was a substitute for religion after the Civil War when "Americans were drawn to German idealism because of a 'loss of faith in traditional cosmic explanations.' "[14] "By the early 1870s, the infiltration of German idealism was so pronounced that Walt Whitman declared in his personal notes that 'Only Hegel is fit for America — is large enough and free enough.' "[15]