- •I.1 Preliminary Remarks
- •I.2 Cases of Consciousness (or Its Absence)
- •I.3 Kinds of Consciousness
- •I.4 Kinds of Unity
- •Figure I.2
- •1.1 Multiple Experiences and the Problem of Unity
- •1.2 Undermining the Problem as Standardly Conceived
- •1.3 The One Experience View
- •1.4 An Account of Synchronic Phenomenal Unity
- •Figure 1.1
- •2.1 The Body Image
- •2.2 A Theory of Bodily Sensations
- •2.3 The Problem of Bodily Unity
- •3.1 Opening Remarks
- •3.2 Perceptual Consciousness and Experience of the Body
- •3.3 Unity and Conscious Thoughts
- •3.4 Unity and Felt Moods
- •4.1 Examples of Unity through Time
- •4.2 The Specious Present and the Problem of Diachronic Unity
- •4.3 An Account of Unity through Time
- •4.4 Some Mistakes, Historical and Contemporary
- •4.5 Carnap and the Stream of Consciousness
- •5.1 Results of Splitting the Brain
- •Figure 5.1
- •5.2 Multiple Personality Disorder, Split Brains, and Unconscious Automata
- •5.3 Indeterminacy in the Number of Persons
- •5.4 Disunified Access Consciousness
- •5.5 Disunified Phenomenal Consciousness: Two Alternatives
- •5.6 The Nontransitivity of Phenomenal Unity
- •6.1 The Ego Theory and the Bundle Theory Quickly Summarized
- •6.2 Objections to the Ego Theory
- •6.3 Objections to the Bundle Theory
- •6.4 A New Proposal
- •6.5 Problem cases
- •6.6 Vagueness in Personal Identity
- •Introduction
I.4 Kinds of Unity
One important issue of investigation recently in cognitive psychology and neurophysiology has been how the visual system brings together information about shape and color. If I view a green, circular object, the greenness and roundness I experience are represented in different parts of my visual system. In my experience, however, the color and shape are unified. I experience a single green, circular object. I notice and report on only one such object. How can this be? How are the color and shape unified as belonging to a single object in my consciousness? This is often called "the binding problem" and the kind of unity it concerns is object unity.9
Object unity is not a necessary feature of P-consciousness. We frequently experience colors and shapes without experiencing them as belonging to the same object, as when, for example, I see a green object next to a round one without seeing a green, round object. So, colors and shapes need not be object-unified in my consciousness as I undergo a P-conscious state.
A second kind of unity is neurophysiologies unity. Conscious states may be said to be neurophysiologically unified if and only if they are realized in a single neural region or via a single neurological mechanism.
A third sort of unity is spatial unity. Consciousness is spatially unified for a given subject if and only if everything experienced by that subject is experienced as belonging to a single, common space. Spatial unity can obtain at a time or through time; it can obtain for consciousness of one sort while failing for consciousness of another. The view that perceptual consciousness is necessarily spatially unified is quite plausible; and it has had some distinguished advocates (most notably Kant).
A fourth kind of unity is subject unity. Two different states of consciousness may be said to be subject unified if and only if they are undergone by the same mental subject. These states could be higher-order ones, involved in /-consciousness, or they could be first-order states. Whatever the states, the thesis that, for any given subject, all his or her states of consciousness are subject unified is trivially true.
Kant held that the unity of consciousness involves having experiences that the subject of the experiences can self-ascribe in thought. This ties the unity of experience to the subject via higher-order consciousness. Let us call this unity higher- order subject unity. Consciousness is higher-order subject- unified for a given subject (at a given time or for a given period of time) if and only if that subject can self-ascribe each of her conscious states in thought (at that time or for that period). Higher-order subject unity is thus much more demanding than subject unity.
Another related thesis is that two states of consciousness are unified if and only if the subject can introspect both states in a single act of introspective awareness. This is introspective unity.
Gestalt unity is the sort of unity that obtains if and only if the experience of a whole is such that had one salient part of the whole been removed from consciousness, the experience would have had a radically different phenomenal character. For example, on one natural way of seeing figure I.1, the viewer has an experience of a vase; but if the right half is removed, the experience becomes one of a face, in profile, turned to the right.
Gestalt unity is an interesting phenomenon, the principles of which have been studied in detail by psychologists. It is more the exception than the rule, however. For example, removing a part of figure I.2—the left half, say—does not produce an experience of a whole with a radically different character. And with intermodal cases, there are few Gestalt effects.10
The final kind of unity I shall distinguish is phenomenal unity. Phenomenal unity is present in all normal cases of phenomenal consciousness. It is usually taken to be a property of experiences or P-conscious states; in my view, it is different from object unity, neurophysiological unity, spatial unity, subject unity, higher-order subject unity, introspective