Blindsight and Empiricism

Blindsight and Empiricism

Imagine a person with blindsight in every sense: no conscious perceptual experience at all but able to receive information subconsciously from the external world. This person nevertheless has ordinary fully conscious reason: she is capable of forming beliefs that count as knowledge in virtue of the informational input. It would not occur to her to suppose that all her knowledge rests on conscious experience; she would not be a traditional empiricist. She might indeed be a rationalist about her powers of knowing, supposing the intellect to be the sole mental faculty implicated in the generation of knowledge (she could still allow that causal relations to the environment are involved). So there is nothing necessary about conscious sensory experience in the production of knowledge of the external world (subliminal perception makes the same point). Sensory qualia are not essential to knowledge of the physical world. On the other hand, the apparatus of reason is essential: concepts, judgment, reasoning, and propositions. You can’t be blind about these things and still know in the ordinary sense. If someone were to claim that sensations of pain and pleasure were the essence of knowledge of physical things, we could quickly refute them by pointing out that a knower could very well lack such sensations and still know, so long as other faculties remained intact—in no way is knowledge based on sensations of pain and pleasure. The same could be said of emotion: it is not essential to the enterprise of knowledge despite its presence in the mind of the typical human knower. Pain, pleasure, and emotion no doubt have a function, but it is clearly not to serve as a foundation for human knowledge. The case of the blindsighted knower shows that the same is true of sensory experience: this too is not the indispensable foundation of human knowledge.[1]

            This suggests that all knowledge conforms to the basic tenets of rationalism: the mental faculty involved in producing knowledge is uniformly reason. It isn’t that some knowledge arises purely from reason and some knowledge consists in a kind of refinement or distillation of sense experience—a different kind of cognitive state—but rather that all knowledge is composed of the same basic materials, though no doubt about different things. Thus mathematical knowledge is essentially the same as knowledge of physical things in its intrinsic nature—viz. an activity of intellect—though the subject matter of the two is different. There is not intellectual knowledge and sensory knowledge, as if the latter is infused with sense experience while the former is not; rather, all knowledge is an affair of the intellect in its inner composition (however differently caused). Moreover, there is no sense in which one type of knowledge mimics or copies sensation; sensation is not internal to any kind of knowledge. There are not two types of knowledge as there are two types of swans (black or white): all knowledge is as the rationalist supposes. Empiricism only seems plausible because we tacitly imbue sensation with the products of the intellect, but this is to presuppose rationalism not find an alternative to it.

            It is quite true that some of our knowledge is about sensation, but that does not imply that this knowledge is itself a form of sensation; it is as intellectual as any knowledge we have. We must not transfer to the medium what belongs to the message, i.e. the subject matter. Our knowledge of sensation (Hume’s “impressions”) is not a version of sensation; it is the application of reason to a certain type of subject matter. Human reason is essentially homogeneous not an amalgam of a sense-based faculty and an intellect-based faculty; and the nature of this faculty corresponds closely to traditional rationalist conceptions from Plato onwards. Simply put, and without any attempt at argumentation, it consists of a set of innate ideas organized by a logical faculty into propositional structures of arbitrary complexity. The rational faculty receives inputs of various kinds, to be sure, but it operates in much the same way across the board. Empiricism is an inadequate theory of the nature of this faculty, and it mistakes the inessential for the essential in the production of knowledge.[2]       

[1] See my “Intuitive Knowledge”.

[2] Plato regarded sense experience as incapable of producing genuine knowledge, relegating it to the realm of mere “opinion”; but he could have gone further and rejected it as any kind of justifying basis for our knowledge claims. Experience is just the wrong kind of thing to provide a basis for reason to work on (as I argue in “Intuitive Knowledge”).