In “What Is It Like to Be a Bat?”, Thomas Nagel argues that consciousness cannot be explained by contemporary physical science. The inner lives of bats must be so different from our own, not least in their reliance on echolocation over sight. Although scientific methods tell us a great deal about bats, the subjective, inner awareness of the bat remains inaccessible to a methodology which views things from the outside.
We believe that these experiences [for example, echolocation, fear, hunger] also have in each case a specific subjective character, which is beyond our ability to conceive. (p. 439)
We can understand ourselves and other people like us. This knowledge does not originate from third-party observation. It comes from our direct knowledge of our own inner experiences. We know just what it is like to be human—simply by virtue of being human.
Why is it conceivable that scientific methods exhaustively explain chemical compounds but stumble when it comes to bats or people? The answer, Nagel argues, is that objectivity requires gaining independence from a specifically human viewpoint.
In other areas the process of reduction is a move in the direction of greater objectivity, toward a more accurate view of the real nature of things. This is accomplished by reducing our dependence on individual or species specific points of view toward the object of investigation. We describe it not in terms of the impressions it makes on our senses, but in terms of its more general effects and of properties detectable by means other than human senses. The less it depends on a specifically human viewpoint, the more objective is our description. (p. 444)
Upon seeing a glass of water, we might feel thirsty; upon being informed a quantity of radium is in the next room, we might feel fearful. But these subjective reactions occur in us; they do not tell us what chemical elements or compounds are.
In the case of conscious experience, however, subjective experience is part of what is to be explained. And whereas in the sciences we move from what we experience to what the thing is (e.g., our experience of water to water’s essence), conscious experience is immediately grasped.
Experience itself does not seem to fit this pattern [i.e., of the objectivity of empirical science]. The idea of moving from appearance to reality seems to make no sense here. (p. 444)
Nagel’s essay has been understood by some to be a decisive rejection of reductive materialism. His argument, however, rests on mistakes about the nature of objectivity, knowing, and the self.
We begin our critique with objectivity. It is a mistake to regard objectivity as achieved in leaving behind the human point of view. True enough, the thirst for water or the reasonable fear of radiation poisoning does not belong to the nature of water or radium. Yet insofar as we are inquirers, insofar as we design experiments and postulate theories in physics or chemistry, we move far beyond what is directly experienced to what we postulate to explain our experiences. Critical inquiry, unlike thirst or fear, is unique to the human viewpoint.
Objectivity in the authentic sense has a negative and a positive side. Negatively, we recognize that the conditions of knowing some X differ from the conditions of X existing. My knowledge of the bat in the chimney is conditioned upon the evidence I have, but the bat’s existence hardly depends on my knowledge of it.
Positively, we know X when we have followed the (utterly human) activity of scientific inquiry through to its conclusion. No specific rule dictates when the conclusion has been reached. This culmination occurs when all relevant questions have been settled. What those questions are depends on what the line of inquiry happens to be, as well as what data is attainable.
This brings us to our seco
nd line of critique: Nagel’s notion of knowledge. Throughout his essay, Nagel conflates familiarity and knowledge. Familiarity lies on the level of experience, imagination, and habitual expectation. I “know what it is like” to fly in a plane. But do I understand why planes fly?
Knowing in any strict sense involves grasping explanations, answering “why” questions. Familiarity, on the other hand, we share with bats.
This distinction between familiarity and knowledge is crucial for understanding what reduction means in the context of science. There are two kinds of reduction: downward reduction, and—to use St. Thomas’ term—reduction to causes. An example of downward reduction would be to say that animals can be explained entirely in terms of physics. Or, put differently, a comprehensive understanding of biology would reveal it to be nothing but applied physics.
Reduction to causes, on the other hand, identifies reality with the elements of an explanation. It is another way of saying that reality is fully intelligible. For Aristotelians, reality reduces without remainder into the causes grasped in the various sciences. Thus, while I might be familiar with real water through everyday experience, it is not the reality of the water with which I am familiar. The reality of water arises first as a question, as what we are after in demanding the explanation for why water expands when it freezes, why it has multiple states, and so on. And the reality of water is grasped only in an understanding that settles all the “why” questions relevant to water and its behaviors.
Finally, we turn to the self. Nagel regards the intimacy of consciousness as intrinsically irreducible. Animals cannot be reduced to physics—and, in all probability, neither can chemical molecules. But consciousness must be reducible to intelligible causes, else reality is not intelligible. It is implausible to regard consciousness as making even less sense than the physical world. And if reality is not intelligible, then it is not the sort of thing into which we can inquire or about which we can make assertions. Consciousness must, then, be grasped in an explanation. It cannot be opaque to reason and tractable only to direct inner awareness.
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All citations to Thomas Nagel, “What Is It Like to Be a Bat?”, The Philosophical Review 83, no. 4 (October 1974): 435-450.
