Transcendental idealism
<p><b>Transcendental idealism</b> is a doctrine founded by German <a href="https://en.wikipedia.org/wiki/Philosophy" title="Philosophy">philosopher</a> <a href="https://en.wikipedia.org/wiki/Immanuel_Kant" title="Immanuel Kant">Immanuel Kant</a> in the 18th century. Kant's doctrine maintains that human experience of things is similar to the way they <a href="https://en.wikipedia.org/wiki/Phenomenon" title="Phenomenon">appear to us</a>—implying a fundamentally subject-based component, rather than being an activity that directly (and therefore without any obvious causal link) comprehends the things as they are <a href="https://en.wikipedia.org/wiki/Noumenon" title="Noumenon">in themselves</a>.</p>
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Although it influenced the course of subsequent <a href="https://en.wikipedia.org/wiki/German_philosophy" title="German philosophy">German philosophy</a> dramatically, exactly how to interpret this concept was a subject of some debate among 20th century philosophers. Kant first describes it in his <i><a href="https://en.wikipedia.org/wiki/Critique_of_Pure_Reason" title="Critique of Pure Reason">Critique of Pure Reason</a></i>, and distinguished his view from contemporary views of <a href="https://en.wikipedia.org/wiki/Philosophical_realism" title="Philosophical realism">realism</a> and <a href="https://en.wikipedia.org/wiki/Idealism" title="Idealism">idealism</a>, but philosophers do not agree how sharply Kant differs from each of these positions.
Transcendental idealism is associated with <i>formalistic idealism</i> on the basis of passages from Kant's <i><a href="https://en.wikipedia.org/wiki/Prolegomena_to_any_Future_Metaphysics" class="mw-redirect" title="Prolegomena to any Future Metaphysics">Prolegomena to any Future Metaphysics</a></i>, although recent research has tended to dispute this identification. Transcendental idealism was also adopted as a label by the subsequent German philosophers <a href="https://en.wikipedia.org/wiki/Johann_Gottlieb_Fichte" title="Johann Gottlieb Fichte">Fichte</a> and <a href="https://en.wikipedia.org/wiki/Friedrich_Wilhelm_Joseph_von_Schelling" class="mw-redirect" title="Friedrich Wilhelm Joseph von Schelling">Schelling</a>, <a href="https://en.wikipedia.org/wiki/Arthur_Schopenhauer" title="Arthur Schopenhauer">Schopenhauer</a>, and in the early 20th century by <a href="https://en.wikipedia.org/wiki/Edmund_Husserl" title="Edmund Husserl">Husserl</a>.</p>