Why have critics argued that Kantianism leads to subjectivism?

Critics have argued that Kantianism leads to subjectivism primarily because of its "transcendental formalism," which emphasizes the role of the thinking subject in constructing experience. By positing that human knowledge is, in part, a product of the mind's own a priori structures—such as space, time, and the categories of understanding—Kant’s philosophy suggests that we only ever encounter phenomena as they appear to us, rather than things-in-themselves.12

Critics contend that this framework has several problematic implications:

• Denial of External Reality: By viewing the transcendental source as playing a constructive role in experience, the theory is accused of obstructing access to the external world and preventing the attribution of objective reality to phenomena.1
• Subjective Construction: The focus on the "transcendental Ego" or thinking subject leads to the view that human knowledge is merely a product of subjective construction.1
• Ethical Formalism: In the realm of ethics, critics like Max Scheler have argued that Kant’s reliance on formal principles—specifically the categorical imperative—is too detached from concrete human concerns, potentially trapping the moral agent within their own rational framework rather than engaging with the reality of others.1

While Kant intended to secure the objectivity of science and morality, these critics maintain that his "Copernican revolution" in philosophy ultimately traps the human mind within its own subjective apparatus.21