In McGinn’s mysterian pluralism, reality has many properties—some graspable, others mysterious, not because we don’t yet know enough about them, but because they are inaccessible to humans by necessity of cognitive closure; we cannot ever grasp them. The cognitive limitations of humans determine knowable and mysterious properties. By identifying them, we avoid making philosophical dead-end turns.
We can now discern the picture of consciousness that McGinn conveys. Consciousness is caused by an inaccessible property, P, which can be explained only by an inaccessible theory.
In sum, consciousness will remain mysterious because any explanation would depend on a brain property that we can neither grasp nor theorize about.
McGinn notes, like Kant, that space and time are conditions of our experience. We learn about events in space and time, but we don’t learn about space and time in the same way. Kant illustrated this by pointing out that the idea of space cannot be derived from things being located side by side or in any other way, because this requires an understanding of space. To think “side by side” is to think spatially. Another example of the fundamental nature of space is that we can also conceive of empty space but not objects without space. Similarly, we can think of time as being a condition of all experience. Experience takes place in time, but the notion of time is not learned through observing events, because to speak of events is to talk about things that already happen in time. Again, time is fundamental, and we can conceive of eventless moments but not events outside time. McGinn accepts the Kantian spatiotemporal characterization of experience and argues that there is a property beyond, causing consciousness. Cognitively speaking, we are spatiotem- poral beings. This does not hinder us from having theories about properties that we cannot perceive, such as electron spin, but it limits our understanding of unobservables to spatiotemporal theories. Try to imagine what it would be like to have a scientific theory about something outside any understanding of time and space whatsoever. This, McGinn suggests, is what it would take to explain consciousness as something we cannot locate like an object, an energy field, or anything else in space. We cannot explain consciousness—the nonspatial phenomenon it is— through human, necessarily spatial, explanations. In McGinn’s view, there could be a theory that explains consciousness, but it would be a nonspatial theory beyond human grasp:
Kant was right, the form of outer sensibility is spatial; but if so, then P [the property that causes consciousness] will be noumenal with respect to the senses, since no spatial property will ever deliver a satisfying answer to the mind-body problem. We simply do not understand the idea that conscious states might intelligibly arise from spatial configurations of the kind disclosed by perception of the world. (McGinn 1989, p. 358)
Not even a paradigm shift will help:
Not only do we need a “paradigm shift” to come to grips with consciousness; we need a fundamentally new structure of thought. (McGinn 1999, p. 59)
McGinn gives further support for this position by suggesting the principle of homogeneity. We expect spatial physical processes to have physical results of the same nature, not to leap out of the space-time continuum. Similarly, we expect consciousness—as a nonspatial phenomenon—to be caused by something nonspatial.