What is it like to be on acid?

Every friend who finds out I have taken psychedelics asks the same question: what does it feel like? I have told the story many times, in many versions, and at some point I got tired of reaching for the same approximations. So I started mapping it instead.

We all already have some model for altered states in our head. You know what coffee does at 7am: sharper, faster, more present. You know what a beer does on a Friday evening: edges soften, urgency drops, thinking slows to something more pleasant. You know the difference between lying half-asleep and properly falling under. And if you have had a vivid dream, you know that "asleep" is not the same as "absent", the mind can be intensely active while the body is completely still.

These feelings can be described as positions in a space defined by variables of our awareness. Once you start mapping them, the structure becomes clear, and it becomes possible to ask: where exactly does a psychedelic (taken within legal frameworks) sit in that space? And why does it feel like nothing else?

What follows is a framework. The neuroscience supports it. The goal is a coordinate system precise enough to place every conscious state, including the ones that resist description, into a shared map.

Two axes you already understand

Start with the most basic dimension: how awake you are. Call it Alertness, running from fully sedated at one end to maximally alert at the other. Deep sleep is near one extreme. A strong coffee at 6am is near the other. Anesthesia goes further still.

The second axis is Engagement: how much your mind is actively oriented toward anything. You can be technically awake but mentally absent, scrolling without seeing, present in body but nowhere in particular. That is low engagement. Flow states, vivid dreams, intense conversations, all sit at the high end.

Together, these two axes give you a 2D map. The substances you already know land in predictable places. Coffee pushes you up and to the right. Alcohol pulls you down and left. A sleeping pill takes you further down still. The graphic below shows a few of these, plotted as vectors from baseline. The direction of each arrow is the direction the substance moves you. The length is roughly how far.

Why two dimensions are not enough

The 2D map breaks down at a specific point. A focused flow state and a panic attack both land in the high-alertness, high-engagement quadrant. They feel nothing alike. An MDMA peak and a deep meditation sit in roughly the same region too. The map cannot tell them apart. Something is missing.

The missing dimension is the one that measures how the brain is organizing itself at a given moment. Not whether you are awake or engaged, but what the underlying structure of your experience is. Is your thinking ordered, linear, self-consistent? Or is it fragmenting, looping, dissolving into noise?

Think of it this way. At one end of this axis sits the depressed brain: rigid, stuck, running the same loops over and over, unable to generate new patterns or escape its own predictions. The world narrows. Nothing surprises. This is not low arousal or low engagement, it is a brain that has lost flexibility. At the other end sits something like acute psychosis: too much signal, too little structure, the filters gone, everything equally loud and equally meaningful. Psychedelics push toward that end deliberately, at lower intensity, with the sedative dose removed.

Robin Carhart-Harris formalized this as the Entropic Brain hypothesis (2014), extended in the REBUS model (2019). The claim is measurable: psychedelics increase neural entropy as seen on EEG and fMRI. The brain's top-down predictive models loosen. More signal gets through from below.

Call this axis Entropy, running from Rigid (depressed brain) to Entropic (psychotic or psychedelic brain). Ordinary waking life sits near the middle. Meditation, interestingly, moves toward order through deliberate cultivation, not suppression. That makes it structurally different from depression even if both score low on entropy.

The full 3D space

With three axes, every substance becomes a vector with three components: (Alertness, Engagement, Entropy). The origin point (0, 0, 0) is baseline sobriety, alert enough for ordinary life, engaged with the world at a normal level, brain activity neither especially rigid nor especially chaotic. The direction of each vector tells you what a substance does. The length tells you how much.

One substance at a time

Let me walk through each vector explicitly, with a small visualization for each.

What it actually feels like

The vector description tells you where you end up. It does not capture the experience of moving there, or what it is like to inhabit that coordinate. What follows is based on personal experience with psychedelics taken in controlled settings.

Time distortion. The engagement axis turns recursive. You become engaged with your own engagement. Each moment of attention contains metadata about attention itself. A minute can feel architecturally complex, layered, far longer than a minute. This is not necessarily time slowing (unless you are under tons of gravity or traveling very fast), it is time gaining texture. We actually do not know yet. Experiences with time loops are a thing, and there may be another biochemical mechanism to experience time at play. The axes bleed into each other.

Ego dissolution. The stable sense of a located self, the thing that normally provides fixed coordinates in the space, begins to dissolve. You are no longer a point with a position. The boundary between subject and object softens, then disappears. What remains is experience without an experiencer. Some people find this terrifying. Others find it revelatory. It depends on where you started.

Geometric visuals and synesthesia. When the entropy axis peaks, the brain's perceptual filters relax. The visual cortex generates structure from noise. Fractals, geometric patterns, color overlays on surfaces that do not have them. Simultaneously, the separations between sensory modalities weaken: sounds acquire visual qualities, emotions have spatial textures, music becomes architecture. The axes bleed into each other.

The trajectory. The experience is not static. It traces a path through the 3D space over twelve hours. The visualization below shows this arc.

This framework is not complete

Three axes is a starting point. The space of conscious experience almost certainly has more dimensions than this. Valence (how good or bad an experience feels) is not captured here, for instance. Nor is the geometry of visual experience, the degree of self-referential thinking, or the sense of meaning and significance that psychedelics often amplify without necessarily moving alertness or engagement much.

The Qualia Research Institute has developed a more comprehensive framework for mapping conscious states, including parameters like symmetry of experience, valence, and what they call the "geometry of qualia." Their work is worth exploring if you want to go deeper. A useful starting point is Andrés Gómez Emilsson's writing on the symmetry theory of valence, which tries to explain why some states feel good and others do not in terms of the mathematical structure of neural patterns.

The three-axis model here trades completeness for clarity. It is designed to answer one specific question: why does a psychedelic feel so categorically different from everything else you have experienced? The entropy axis does most of that work.

Why this framework matters

Depression and high-dose psychedelics are opposites on the entropy axis. That single observation does a lot of explanatory work: it suggests why psilocybin-assisted therapy produces remission in treatment-resistant depression, why a single session can break patterns that years of talk therapy could not, and why the effect sometimes persists for months. You are not just changing the content of thought. You are changing the regime the brain operates in.

The vector framing also has a practical use: vectors add. Coffee plus cannabis shifts you along multiple axes simultaneously. The alertness from caffeine partially counteracts the disengagement from THC, while the entropy from cannabis remains. This is not just intuition, it is a structural prediction the framework makes, and it matches what people who combine them report.

Building this cartography is not a philosophical luxury. For psychedelic therapy, for understanding what suffering actually is at a structural level, for the long-term question of what kinds of consciousness are possible in artificial systems, having a coordinate system matters. The territory does not change. But a map helps you navigate it, and helps you explain to someone else what you found there.