Corey J. Maley and Gualtiero Piccininian organism as a whole that differentiates between organisms that are awake or in REM sleep
and organisms that are in non-REM sleep, in a coma, or otherwise unconscious. State con-
sciousness is a property of some mental states such that there is a qualitative feel to them. Our
main focus is on state consciousness, which can be illustrated by an example.
Consider a familiar event: biting into a ripe orange. The orange tastes a certain way. We might
say, somewhat unhelpfully, that it tastes like an orange: that is, it tastes the way oranges taste, it tastes
like other oranges, and so on. If a person has never tasted an orange before, then no amount of
description or figurative language will fully enable that person to know what it’s like to taste an
orange: she simply has to experience that taste for herself. The qualitative feeling of tasting an
orange is what we mean by phenomenal consciousness.
Before proceeding, it is also worth flagging what phenomenal consciousness is not.
Phenomenal consciousness is not simply awareness or wakefulness: as mentioned above, this
pertains to creature consciousness. By awareness, we mean the ability to detect and respond
to stimuli—both internal and external stimuli. By wakefulness, we mean a global neural state
of arousal that normally allows organisms to have awareness, although under special circum-
stances there can be limited awareness without wakefulness and wakefulness with limited or
no awareness, as in unresponsive wakefulness syndrome (Laureys et al. 2010). Lack of both
awareness and wakefulness occurs when one is asleep or otherwise made unconscious by, say,
drugs or a concussion. Wakefulness and awareness—and more generally, creature conscious-
ness—are probably neither necessary nor sufficient for phenomenal consciousness. They are
not necessary because during REM sleep we are neither awake nor aware, yet we have phe-
nomenal experiences. They might not be sufficient because very simple animals can be awake
and aware, thus possessing creature consciousness, but it is far from clear that they are also
capable of phenomenal consciousness.
In addition, phenomenal consciousness is not simply access consciousness (Block 1995). To
have access consciousness is to have information available in the cognitive system for reasoning,
speech, and intentional action control. In many circumstances, phenomenal consciousness and
access consciousness go together: when we experience the taste of an orange, we can also reason
about it, talk about it, and plan accordingly; conversely, when we have global access to infor-
mation, we have a qualitative experience associated with that information. But there might be
kinds of information that are accessible without being experienced, or experiences that are not
accompanied by cognitive access. Whether phenomenal consciousness and access consciousness
can truly be dissociated is controversial; what matters here is that the two notions are conceptu-
ally distinct, and that our main interest is phenomenal consciousness.
3 Evolutionary ExplanationsProviding an evolutionary explanation of any biological trait faces two challenges. First, several
types of evolutionary explanation are possible, and it’s not always easy to determine which type
applies to a given trait. Second, each kind of evolutionary explanation requires specific sorts of
evidence, including evidence about the past, which is difficult to obtain.
Some traits are selected for, meaning that (i) their existence enhances the survival and fit-
ness of organisms with the trait relative to those without that trait, (ii) the traits are genetically
heritable, and (iii) organisms with the traits reproduce more than organisms without the trait
because of the advantage conferred by the trait.^1 We will refer to the contribution to survival and
fitness that a trait confers as its function (Maley and Piccinini, forthcoming). Traits that evolve
via natural selection because of the function they perform—i.e., traits that are selected for—are
known as adaptations.