Immanuel Kant used the term "transcendental" in a specific philosophical sense to refer to knowledge that is not about objects themselves, but about the conditions that make our knowledge of objects possible. In other words, "transcendental" knowledge concerns the a priori (prior to experience) structures or modes of cognition that the mind uses to process sensory data and produce experience.

Kant's transcendental philosophy investigates how the mind actively shapes our experience by imposing certain innate forms and categories. For example, in his "Transcendental Aesthetic," Kant argues that space and time are not external realities existing independently "outside" us, but rather pure forms of human sensibility—subjective frameworks that structure all our perceptions. These forms are necessary conditions for the possibility of experiencing objects at all. Thus, space and time are "transcendentally ideal" but "empirically real"—real as conditions of experience but not as things in themselves independent of the mind157

More broadly, Kant's transcendental method involves examining the conditions that must be in place a priori for experience and knowledge to be possible. This contrasts with empirical knowledge, which is derived from sensory experience. Kant famously proposed a "Copernican revolution" in philosophy: instead of assuming that knowledge must conform to objects, he argued that objects conform to our knowledge, meaning that our cognitive faculties shape how objects appear to us5.

Transcendental idealism, Kant's key doctrine, holds that while we can know empirical objects as they appear to us (phenomena), we cannot know things as they are in themselves (noumena), independent of our cognitive faculties. Hence, the "transcendental" is about the mind's role in constituting experience and the limits of human cognition13.

In summary, Kant's use of "transcendental" refers to the study of the a priori conditions and structures of the mind that make knowledge and experience possible, rather than knowledge of objects themselves. It is a methodological approach to understanding how cognition works at the most fundamental level56.

Contemporary sciences provide several lines of support and resonance with Kant’s notion of the transcendental, particularly in how they recognize the active role of the mind or cognitive frameworks in shaping experience and knowledge.

1. Cognitive Science and Neuroscience
Modern neuroscience and cognitive science align closely with Kant’s idea that perception is not a passive reception of sensory data but an active construction shaped by innate cognitive structures. Research shows that the brain constantly predicts and interprets sensory input based on prior knowledge and internal frameworks, paralleling Kant’s a priori categories that organize experience. This predictive processing model supports Kant’s view that the mind imposes necessary conditions on how we experience the world, rather than merely reflecting it passively3. Moreover, neuroscientific studies on self-consciousness and the unity of experience echo Kant’s concept of the transcendental unity of apperception, which is the necessary condition for coherent experience of a unified self36.

2. Philosophy of Science and Quantum Mechanics
Kant’s transcendental idealism has been revisited in the context of modern physics, especially quantum mechanics. Some scholars argue that Kant’s framework offers a natural way to understand the epistemic challenges posed by quantum phenomena, such as complementarity and the role of the observer. The indeterminacy and contextuality in quantum mechanics resonate with Kant’s idea that we cannot know things as they are in themselves (noumena), only as they appear through the conditions of our cognition (phenomena)2. Additionally, interpretations of quantum physics have been developed that apply Kantian ideas ontologically, distinguishing between the classical realm (where deterministic laws apply) and the quantum realm (where spontaneity and potentiality manifest), which can be seen as reflecting Kant’s distinction between the phenomenal and noumenal realms4.

3. Predictive Processing and Idealism
Recent theoretical developments such as prediction error minimization in cognitive science have been argued to align with key Kantian transcendental ideas. These theories suggest that the brain actively constructs representations of the world, minimizing discrepancies between expectation and sensory input, which mirrors Kant’s notion that the mind structures experience through inherent categories5. This approach supports a form of philosophical idealism that sees the mind as playing a constitutive role in shaping reality as we experience it.

In summary, contemporary neuroscience, cognitive science, and interpretations of quantum physics provide empirical and conceptual support for Kant’s transcendental philosophy. They affirm the active, structuring role of the mind in experience and knowledge, the limits of what can be known about things in themselves, and the significance of a priori cognitive frameworks—core elements of Kant’s transcendental idealism2345.(Perplexity)