The human mind, a realm of "unseen visions and heard silences," presents a profound mystery. This internal landscape, characterized by "ineffable essences," "touchless rememberings," and "speechless monologue," is the subject of intense philosophical and psychological inquiry. Julian Jaynes, in his seminal work The Origin of Consciousness in the Breakdown of the Bicameral Mind, begins by describing this enigmatic phenomenon before delving into its origins, suggesting that consciousness, as commonly understood, may not be a prerequisite for all mental life and might have evolved relatively recently in human history.

The apparent paradox in Jaynes's assertions often stems from differing definitions of "consciousness." While the common understanding is valid, a more specific definition, employed by figures like Carl Jung and Sigmund Freud, and utilized in this discussion, is crucial for a deeper understanding of the human mind. Philosopher Ned Block identified two distinct mental phenomena that the term "consciousness" can refer to: phenomenal consciousness and access consciousness.

Phenomenal Consciousness: The Subjective Experience

Phenomenal consciousness encompasses any mental experience perceived from a subjective, internal viewpoint. This includes the qualitative feel of sensory perceptions.

• Vision: The subjective experience of color, shape, and depth, allowing for the creation of a mental representation of the external world.
• Taste and Smell: Subjective experiences of flavors and aromas, enabling the creation of new sensations through combinations, as seen in cooking.
• Hearing: The perception of loudness, pitch, and timber from air vibrations, which can evoke profound emotional responses, particularly when experienced as music.
• Touch: The sensation felt through the skin, including temperature, and the feeling of balance and acceleration.

Beyond sensory input, inner states also contribute to phenomenal consciousness:

• Hunger: An unpleasant feeling motivating the need for sustenance.
• Pleasure: A positive feeling derived from activities like eating or social interaction, driving behavior.
• Pain: A visceral, often overwhelming experience that signals bodily damage and motivates avoidance.
• Emotions: Distinct subjective feelings such as anger, happiness, sadness, jealousy, awe, pride, loneliness, and love, which can vary significantly in intensity and nuance.
• Thoughts: Internal experiences including inner monologue and visualization. While some individuals possess a "mind's eye" for visualization, others experience aphantasia, the inability to form mental images. Similarly, some individuals lack an inner monologue.

The sum total of these subjective mental experiences constitutes phenomenal consciousness. This phenomenon is deeply mysterious, with the nature of qualia—the raw, subjective qualities of experience, such as the color blue or the taste of salt—remaining particularly enigmatic. The "hard problem of consciousness" refers to the difficulty in explaining how physical matter can give rise to these subjectively experienced qualia.

The Enigma of Qualia

Qualia present a significant challenge to understanding consciousness. For instance, the experience of color is internal; it is uncertain whether an object possesses an inherent color independent of our perception. The "Mary's room" thought experiment explores this, questioning whether knowing all physical facts about color equates to experiencing it.

Animal sensory experiences further highlight this complexity. Birds, with eyes sensitive to UV light, likely perceive colors beyond human capacity. Similarly, pit vipers detect temperature at a distance, and migratory birds sense the Earth's magnetic field. Thomas Nagel's essay "What Is It Like to Be a Bat?" argues that understanding the physical mechanisms of a bat's echolocation does not equate to understanding its subjective experience. While neuroscience can map the physical processes underlying experiences like pleasure (e.g., dopamine's role), it does not fully explain the subjective feeling itself.

The materialist perspective that physical processes are mental experiences is challenged by the distinction between the physical brain activity and the subjective experience of, for example, an elephant. The qualia of the elephant appears to exist in a mental space, distinct from the physical matter involved. This suggests that the mind, while correlated with physical processes, may represent an emergent, non-material phenomenon.

The subjective nature of consciousness leads to the philosophical problem of other minds: one can only infer that other beings possess consciousness, leading to concepts like solipsism (the belief that only one's own mind is sure to exist) and philosophical zombies (beings that appear conscious but lack subjective experience). These considerations give rise to theories such as panpsychism (all matter is conscious) and universal idealism (the universe as a whole is conscious), none of which are definitively provable. The complexity of animal nervous systems suggests a gradient of consciousness, but drawing a precise line remains challenging.

Access Consciousness: Awareness and Recognition

Access consciousness, in contrast to phenomenal consciousness, refers to the ability to be aware of, know, understand, or recognize information. It is an additional layer atop phenomenal consciousness, enabling awareness of specific mental experiences.

• Awareness: The ability to focus attention on particular stimuli, even those in peripheral vision, demonstrating that conscious awareness is distinct from raw sensory perception. This selective attention allows for filtering out irrelevant perceptions, such as background conversations at a party or specific instruments in music.
• Recognition: The sense of familiarity associated with identifying objects, smells, sounds, or language. This involves linking current perceptions to past experiences. Misidentification, such as mistaking a dust clump for a spider, highlights that recognition is not always accurate but the sense of knowing is characteristic of access consciousness.
• Understanding: The comprehension of meaning, particularly evident in language. The ability to grasp the meaning of words and sentences is a key aspect of access consciousness. Before language acquisition, sounds are perceived but not understood.
• Knowledge and Facts: Access consciousness also involves awareness of facts, such as the current date, location, or scientific concepts like microorganisms, DNA, gravity, and evolution. This awareness can be gained through perception or through abstract reasoning and learning.

Consciousness, Self-Awareness, and the Unconscious

Consciousness is closely tied to the sense of self-awareness or being self-conscious, where attention is directed inward. This self-awareness is often considered a developmental milestone, emerging in childhood. However, much of our mental life operates unconsciously. Driving, for instance, can become an automatic, unconscious process for experienced drivers, with consciousness only engaging when novel or challenging situations arise.

This suggests that humans may have evolved from a state of operating purely on instinct to one of conscious awareness and inquiry. The story of Adam and Eve, in this context, can be interpreted as a narrative of the emergence of self-awareness.

Sentience: The Foundation of Subjective Experience

The distinction between phenomenal consciousness and access consciousness is crucial. The author proposes using the term "sentience" for phenomenal consciousness, aligning with philosopher Peter Godfrey Smith's distinction concerning other minds. Sentience refers to the basic capacity for subjective experience—the fact that "life feels like something."

Questions about whether animals like squid, lobsters, or bees feel pain are, in this framework, questions about their sentience: "does damage feel like anything to a squid?" Sentience is considered a precursor to consciousness. The sum total of sentient experience, encompassing both conscious and unconscious aspects, can be referred to as the "psyche."

Distinguishing between sentience and consciousness is consequential for understanding the complexity of the human mind and the potential experiences of other beings.