Page "Consciousness" Paragraph 20
Philosophers who consider subjective experience the essence of consciousness also generally believe, as a correlate, that the existence and nature of animal consciousness can never rigorously be known.
Thomas Nagel spelled out this point of view in an influential essay titled What Is it Like to Be a Bat ?.
He said that an organism is conscious " if and only if there is something that it is like to be that organism — something it is like for the organism "; and he argued that no matter how much we know about an animal's brain and behavior, we can never really put ourselves into the mind of the animal and experience its world in the way it does itself.
Several psychologists and ethologists have argued for the existence of animal consciousness by describing a range of behaviors that appear to show animals holding beliefs about things they cannot directly perceive — Donald Griffin's 2001 book Animal Minds reviews a substantial portion of the evidence.