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This page lists various connotations of the term "consciousness" in use in scientific research today.

The fact that so many different conceptions of this term are being applied highlights the striking contrast between the conceptual exposition and the familiarity of consciousness.[1]

Some of the distinctions below are inspired by (Metzinger, 2009).[1]

Logical structures of the term consciousness

We first distinguish various different logical structures of the term "consciousness" that are being employed, such as the type of predicate and the class of referents.

Unary predicate of individual beings

Often, the term "consciousness" is being used as a unary predicate, i.e. it is a predicate that takes one "variable". This variable often describes organisms, persons, subjects or the like.

Example: Consciousness in this sense could refer to whether a person is in a state of wakefulness, cf. below.

Unary predicate of mental states

Consciousness is also being used as a property of mental states.

First variant: According to a first variant, a mental state is conscious if its content is available for rational thought and control of behavior. This is closely related to access consciousness, cf. below.

Second variant: According to a second general variant of the unary predicate of mental states conception, mental states are conscious if we experience what it is like to be in the respective state, or alternatively if there is something it is like to be in that state. A third, closely related but distinct notion would be to define a mental state as conscious if we know of the mental state's qualitative features.

Binary predicate of individual beings

The term "conscious" is also being used as a binary predicate, i.e. a predicate which takes two "variables". In one way of using the term, one of the variables refers to individual beings such as persons or organisms, and the other refers to objects of perception or thinking, cf. consciousness in the intentional sense below.

Example: A person is conscious of a red tomato.

Binary predicate of mental states

The term consciousness is also being used as a binary predicate which refers to persons or organisms, on the one hand, and to their mental states on the other hand.

This is the case, e.g., if "consciousness" is taken to denote the attention of a person on his/her own mental states. Cf. introspective consciousness or attentive consciousness below.

Meanings of the term consciousness

In what follows, we aim to list and distinguish the various types of meaning of the term "consciousness" that are being considered in the literature. While many overlap in their respective meaning or reference to some extent, it is important to note that they are all different when it comes to details. Thus a theory or empirical study which addresses one of them may be misleading if interpreted to apply to another.

Conscious perception of a stimulus

In many neuroscientific studies, the term consciousness is understood as referring to the conscious perception (or not) of a particular stimulus. Typical examples are visual masking experiments.

Arguably, this conception of consciousness is the primary target of global neuronal workspace theory and its prediction of conscious "ignition", a sudden, late and sustained firing in GNW neurons should a stimulus be perceived consciously.[2]

Access consciousness

The term has originally been introduced by (Block, 1995)[3]. Following (Shea, 2012)[4], it could be defined as follows:

Subject instantiates property , being access conscious of , iff
  1. has a mechanism for making information directly available for us in directing a wide range of behaviours; and
  2. is making the information that directly available for directing a wide range of potential behvaiours of .

Some criticize this notion of consciousness and argue that it should merely be called "access", rather than "access consciousness".[5]

The above defines a binary predicate referring to subjects, on the one hand, and phenomenal properties () on the other. Alternatively, access consciousness can be defined as a unary predicate referring to mental states, where a mental state is (access) conscious if its content is available for rational thought and control of behavior. Intentional mental states can be conscious according to this conception, but also beliefs or sensory states such as sensations.[1]

Introspective consciousness

Introspective consciousness is a perception-like awareness of current states and activities in our own mind. The current activities will include sense-perception, which (...) is the awareness of current states and activities of our environment and our body.[6]

For a distinction of various forms of introspection and general information on the neuroanatomical basis of consciousness, cf. the page introspection.

Attentive consciousness

The term consciousness is also used to describe a person being attentionally aware of her mental states.[1] Consciousness understood in this sense can be both pre-conceptual or conceptually structured. This conception is related to introspective consciousness as well as to higher order knowledge of one's own mental states.

'What it is like to be' consciousness

Cf. the page what it is like to be. This can be applied, e.g., to mental states: Mental states are conscious if we experience what it is like to be in the respective state, or alternatively if there is something it is like to be in that state. A third, closely related but distinct notion would be to define a mental state as conscious if we know of the mental state's qualitative features ("Kenntnis der Erlebnisqualitäten" in German[1]).

The content of a mental state which generates the property required here is often claimed to be private (non-public) in the sense that it is only available for the person that exhibits this mental state.

Phenomenal consciousness

At least two connotations of phenomenal consciousness exist.

General definition

The general sense of the term from phenomenology, cf. the page phenomenal consciousness, meaning from phenomenology.

Definition in Chalmers' axiomatization

A notion defined in (Chalmers 1996)[7], cf. the page phenomenal consciousness, Chalmers' definition.

Consciousness in the intentional sense

Consciousness in the intentional sense refers to the relation of a person with objects of perception or thinking. This connotation of consciousness includes both pre-conceptual attention of external objects or states of one's body, as well as conceptually structured consciousness of objects (e.g. in a description).[1] It is an intentional notion of consciousness because according to this notion, consciousness is always about something.

Pure subjective experience

"Pure subjective experience" is sometimes used to characterize or illustrate a notion of phenomenal consciousness. The word pure may arguably be taken to imply that this notion does not refer to all of conscious experience, but only to some properties or aspect thereof, possibly those aspects which do not have a function or structure (cf. Chalmers' axiomatization) or those aspects which are non-collatable.

Conscious experience

Conscious experience, or simply experience, refers a comprehensive notion of consciousness that tries to comprise all others. Cf. the page conscious experience.

Conscious experience in this sense is what Integrated Information Theory tries to address.


Consciousness sometimes refers to the conceptually structured and reflexive awareness of one as a single, persistent person with certain beliefs, intentions, etc.[1]

Conscious mechanism

Some publications talk about a brain mechanism being conscious or not conscious. Most likely, this can be taken to refer to neural correlates of consciousness (NCC), where a mechanism "is conscious" if it is part of the NCC, though in the studies in question this notion is often used in a somewhat intuitive sense without explicit consideration of the definition of a NCC.

Conscious and unconscious processing

Similar to the conscious mechanism conception of consciousness, some papers distinguish conscious (neural) processing from unconscious (neural) processing. This can probably also be fleshed out in terms of the neural correlate of consciousness and seems to be intimately bound to the conscious perception of a stimulus conception of consciousness.

State vs. creature consciousness

Creature consciousness,[8] also called individual consciousness,[6] refers to the wakefulness conception of consciousness when applied to individual beings.

State consciousness generally denotes a notion of consciousness which is a unary predicate of mental states. It thus "classifies one's (mental) states as of one type or another"[6] and "functions as a type-identifier for mental states". It is likely that here, too, (Rosenthal, 2002)[9] and (Güzeldere, 1995)[6] refer to the wakefulness conception of consciousness, though it can be interpreted also to refer to some of the other connotations of consciousness introduced above.


The term consciousness is often used to denote a person/organism being in a state of wakefulness, capable of processing and reacting to stimuli. This is also circumscribed by the terms "awake" and "alert".[6]


There are many different connotations of qualia, some of which can be applied to several different connotations of the term consciousness. Cf. the page qualia.

Level of consciousness

This conception of consciousness is utilized in formal model building, such as Integrated Information Theory. There are at least two different conceptions thereof.

... of an individual being

The first conception is a further development of the wakefulness conception of conscious experience. Whereas the latter is a predicate, i.e. a function symbol which takes values or , depending on whether an individual being is conscious in this sense or not, the level of consciousness conception of consciousness attempts to introduce more fine-grained distinctions. It describes various different states of consciousness (of an individual being as a whole), including coma, sleep, drowsiness and full wakefulness, among many others.

The individual being conception of the level of consciousness is often modeled as a real number, with a lower number indicating a lower state of consciousness of the person/organism/system in question. However, it is questionable whether this mathematical structure is appropriate. If one demands a operational grounding of the mathematical structure, a preorder might be more appropriate.

... of an constituent/aspect of conscious experience

The level of consciousness conception can arguably also be applied to constituents of, or aspects of, conscious experience in order to describe how intense a particular constituent or aspect of experience is being experienced within the whole of experience. This is being done, e.g., in IIT 3.0, where the constituents are called 'concepts' and where the of a mechanism that constitutes a concept is a real number which arguably serves this purpose.


  1. 1.0 1.1 1.2 1.3 1.4 1.5 1.6 Metzinger, Encyclopedia entry Bewusstsein, 2009, in H.-J. Sandkühler (Editor), Enzyklopädie der Philosophie. Hamburg: Meiner.
  2. Dehaene, Stanislas, Jean-Pierre Changeux, and Lionel Naccache. "The global neuronal workspace model of conscious access: from neuronal architectures to clinical applications." Characterizing consciousness: From cognition to the clinic?. Springer, Berlin, Heidelberg, 2011. 55-84.
  3. Block, Ned. "On a confusion about a function of consciousness." Behavioral and brain sciences 18.2 (1995): 227-247.
  4. Shea, Nicholas. "Methodological encounters with the phenomenal kind." Philosophy and phenomenological research 84.2 (2012): 307.
  5. Citation missing.
  6. 6.0 6.1 6.2 6.3 6.4 Güven Güzeldere; Is consciousness the perception of what passes in one's own mind?, 1995, citing Amstrong D. The nature of mind and other essays, 1980.
  7. Chalmers, David J. The conscious mind: In search of a fundamental theory. Oxford university press, 1996.
  8. Rosenthal, Why are verbally expressed thoughts conscious?, 1990.
  9. Rosenthal, Explaining Consciousness, 2002.