Meet Kant’s Fiercest Opponents

I’ve got a headache, and I blame Immanuel Kant.

Not just because reading the Critique of Pure Reason feels like shoving my brain into a meat grinder, but because the man managed to piss off almost every major philosopher that came after him.

And that takes talent.

The world of philosophy is a battlefield, and Kant was the guy who walked in, planted his flag, and said, “Reality? You only know what your mind lets you know.”

Some nodded along. Others sharpened their knives.

This article is about the ones who sharpened their knives.

1. Hegel: “Nice Try, Kant, But You Missed a Spot”

Hegel looked at Kant’s whole noumena vs. phenomena thing and laughed.

Kant said we can’t really know things-in-themselves, only our perceptions of them.

Hegel said, “That’s cute, but no,” and built an entire system to prove that absolute knowledge is possible—if only you think hard enough.

Hegel basically saw Kant as a guy who ran half a marathon and collapsed just before the finish line.

Instead of stopping at “we can’t know reality,” Hegel wanted to bulldoze through and say, “Actually, we can, through dialectical reasoning.” And he was very smug about it.

2. Schopenhauer: “This Guy is Full of It”

Schopenhauer thought Kant was onto something—until he wasn’t.

He agreed with the whole “our minds shape reality” idea but thought Kant was too soft about it.

Schopenhauer took that concept and went full nihilist, arguing that what really drives existence is blind, stupid Will.

He basically called Kant a coward for not going all the way. If Kant was a guy staring into the abyss, Schopenhauer was the guy who cannonballed into it.

3. Nietzsche: “Why So Serious?”

Nietzsche was not a fan of Kant’s moral system.

The whole categorical imperative—the idea that you should act only according to rules that could be universal—felt, to Nietzsche, like a fancy way of keeping people obedient.

He wanted a world of Übermenschen, people who lived beyond conventional morality, while Kant wanted everyone playing by the same rigid rulebook.

Nietzsche basically said, “Kant, your ethics are just religion with extra steps.” And for Nietzsche, that was about the worst insult imaginable.

4. The Utilitarians: “This is Impractical Nonsense”

If Kant’s ethics had a natural enemy, it was utilitarianism.

Kant argued that morality should be based on duty, not consequences.

Utilitarians—Mill, Bentham, the whole gang—said, “Okay, but what if a little white lie saves someone’s life?”

Kant’s response? “Too bad. Lying is always wrong.”

Utilitarians thought this was absurd.

They wanted ethics that actually worked in real-life situations, not some abstract rules that tell you to be honest even if it gets your grandma killed.

5. Johann Hamann

Hamann was one of Kant’s earliest critics, and he took things personally.

He thought Kant’s philosophy was a total disaster for faith, reason, and human meaning.

To Hamann, Kant wasn’t just doing philosophy—he was tearing down everything that made life spiritual and replacing it with cold, mechanical reasoning.

Kant, in Hamann’s view, stripped the universe of divine mystery and left us with nothing but a bunch of categories and logical boxes.

He saw Kant as the guy who locked God out of the room and then wondered why it felt so empty.

6. A.N. Whitehead: “The World is More Than Just a Mental Construct”

Whitehead, the guy who co-founded process philosophy, wasn’t a fan of Kant’s idea that the external world is a theoretical construct shaped by our perception.

He thought Kant turned reality into something too rigid and disconnected from actual experience.

Whitehead wanted a philosophy that embraced change and fluidity, while Kant was out there building neat little mental filing cabinets.

7. Christine Korsgaard: “Kant Was Right, But Also Wrong”

Jumping to the present, Korsgaard is a major Kantian—but with some big caveats.

She agrees with Kant’s ethics, but she thinks he got some things wrong, especially when it comes to animals.

Kant thought animals had no intrinsic moral worth because they weren’t rational. Korsgaard thinks this is ridiculous and argues that a truly Kantian moral system should include ethical duties toward animals.

Basically, she’s trying to fix Kant’s mistakes without throwing out the whole system.

Summary Table

Opponent	Main Critique of Kant
Hegel	Kant stopped short of absolute knowledge
Schopenhauer	Kant was afraid to go full nihilist
Nietzsche	Kant’s ethics were just disguised Christian morality
Utilitarians	Kantian ethics are impractical
Hamann	Kant’s ideas killed religious faith
Whitehead	Kant’s view of reality was too rigid
Korsgaard	Kant’s ethics should include animals

So what do we make of all this?

Kant was like a guy who built a massive, beautiful, impossible tower in the middle of philosophy. Some people wanted to knock it down. Others wanted to climb to the top and add their own floors.

And some, like Nietzsche, just set the whole thing on fire and danced in the flames.

The thing is, even if you hate Kant, you have to deal with him. He’s like the elephant in the room—except the elephant is also your landlord, and he’s demanding rent.

And the moment you think you’ve escaped him, you’ll wake up in a cold sweat at 3 AM thinking about a priori synthetic judgments.