Chapter
Six
The unity
to jump between neurons at the small gaps between them, the synapses. Cross-
ing a synapse takes at least half a millisecond, so the more neurons are involved
in a given process, the longer that process takes (Welsh, 2015).
But when we look at the mind side of the divide, everything seems to be unified.
It seems as though, right now, there is one ‘me’ and one more or less continuous
stream of experiences happening to me now. The German philosopher Thomas
Metzinger claims that experience requires there to be unity in what is experi-
enced: ‘In order for a world to appear to us, it has to be one world first’ (2009, p.
27). He also says that unity can only ever be experienced as temporally present:
‘One thing cannot be doubted from the first-person perspective: I always experi-
ence the wholeness of reality now’ (1995a, p. 429). The question is, how can such
unity, experienced right now, arise from such diversity of non-instantaneous
processing?
We will tackle this question from a variety of perspectives, leaving for later the
important questions about the unity of self (Chapter 16). We will explore how
the different features of objects are brought together to make a single object
(the binding problem), and how the different senses are brought together to
make a unified experienced world (multisensory integration). We will investi-
gate how subjective and clock time are integrated with each other. Finally, we
will consider what happens when consciousness is more or less unified than
normal, using examples from synaesthesia, split brains, amnesia, and neglect.
These atypical cases may make us question what we assume about normal
experience.
Among the many theories about unity, a tempting but probably unworkable
option is dualism. Substance dualists mostly believe that consciousness is intrin-
sically unitary, each person having their own single consciousness distinct from
their physical brain. Indeed, it was partly the argument from unity that led Des-
cartes to his dualism. It was also the argument from unity that led to Popper and
Eccles to their ‘dualist interactionism’. Their preferred solution was that ‘the unity
of conscious experience is provided by the self-conscious mind and not by the neural
machinery of the liaison areas of the cerebral hemisphere’ (1977, p. 362). They argued
that the mind plays an active role in selecting, reading out, and integrating neural
activity, moulding it into a unified whole according to its desire or interest. The
problem for Popper and Eccles, as for all dualists, is how this mind–brain interac-
tion takes place. The theory provides no explanation of how the separate mind
carries out its selecting and unifying tasks, and for this reason very few people
accept it.
Another dualist, though not a substance dualist, was Benjamin Libet, who believed
that conscious unity was achieved through the effects of a ‘conscious mental field’
(CMF). Libet was a scientist unafraid of putting his ideas to the empirical test, and
proposed the following experiment: take an isolated piece of cortical tissue that
is completely cut off from the rest of the brain but kept fully functioning and
alive, then activate it electrically or chemically. If there is a CMF, this stimulation
should produce a conscious experience in the person who has the rest of the
brain. ‘Communication would then have to take place in the form of some field
that does not depend on nerve pathways’ (Libet, 2004, p. 172). This sounds like a
form of telepathy within one brain, and presumably most scientists would expect
the experiment to fail. Nevertheless, it could be tested.
‘The unity of
consciousness is illusory’(Hilgard, 1977, p. 1)‘I cannot distinguish in
myself any parts, but
apprehend myself to be
clearly one and entire’(Descartes, 1641/1970, p. 196)