Nagel’s Bat Argument (against Physicalism)

  1. Physicalism is the thesis that everything that exists is physical.
  2. Physical facts then, are objective truth (“the kind that can be observed and understood from many points of view and by individuals with different perceptual systems”)
  3. Even if we knew everything about how the bat’s sonar system works, we would not know what is is like for the bat to perceive using this system.
    1. ‘What it’s like’: in this case, something is conscious (a bat) if and only if there is something it’s like to be that being (only a bat knows what it is like for a bat to be a bat)
    2. One, for example, cannot imagine a chair to know what it is like for a chair to be a chair.
    3. For a state to be conscious is for it to have a subjective character (to seem or feel a certain way to the subject). A conscious experience is a state that is both subjective and qualitative.
  4. Therefore, complete knowledge of the physical facts about a bat’s perceptual system would not yield knowledge of certain facts about a bat’s experiences

Physicalism leaves out the subjective facts, so it’s a mystery how it could be true (given that qualia and the subjective experience exists).

Related: Frank Jackson’s Knowledge Argument


A famous Taoist story about happiness and knowing what it is like to be a fish

  • Zhuangzi and Huizi were strolling on a bridge over the River Hao, when the former observed, “See how the minnows dart between the rocks! Such is the happiness of fishes.”
  • “You not being a fish,” said Huizi, “how can you possibly know what makes fish happy?”
  • “And you not being I,” said Zhuangzi, “how can you know that I don’t know what makes fish happy?”
  • “If I, not being you, cannot know what you know,” replied Huizi, “does it not follow from that very fact that you, not being a fish, cannot know what makes fish happy?”
  • “Let us go back,” said Zhuangzi, “to your original question. You asked me how I knew what makes fish happy. The very fact you asked shows that you knew I knew—as I did know, from my own feelings on this bridge.”

Why did Zhuangzi, who wrote it down, show himself to be defeated by his logician friend?