Alexander of Aphrodisias: The Ancient Philosopher Who Mapped Mental Imagery

How a 2nd-Century Thinker Accidentally Revealed What Makes Aphantasic Minds Different

In our History of Aphantasia, we traced the concept of phantasia back to Aristotle in 340 BC. But there's a fascinating chapter we haven't explored—one that bridges the ancient world to modern neuroscience and helps explain exactly what makes aphantasic minds different.

Meet Alexander of Aphrodisias, a Greek philosopher working around 200 AD whose recently analyzed writings created the most detailed ancient account of how mental imagery works. Ironically, by explaining the mechanism he assumed everyone possessed, he inadvertently documented what makes aphantasic minds different.

The Missing Link in Mental Imagery History

When Aristotle introduced phantasia (imagination), he described it as a distinct mental capacity—something between pure perception and pure thought. But Aristotle left a crucial question unanswered: How does phantasia actually work? How can we think about things that aren't physically present?

This is what philosophers call the "presence in absence" problem, and it's exactly what aphantasics experience differently. When you remember your breakfast from this morning or imagine your friend's face, how does your mind access that information when the actual breakfast and friend aren't there?

For most people, the answer involves mental imagery. For aphantasics, it clearly doesn't. But for 1,800 years this variation in human experience went unrecognized—people with aphantasia existed, but the condition had no name and little scientific understanding.

This assumption that everyone could visualize permeated ancient rhetoric and philosophy, from ekphrasis—the art of evoking vivid mental images to the philosophical theories that tried to explain how imagination worked.

Alexander's Theory: Mental Residues

Alexander of Aphrodisias developed a sophisticated answer to this puzzle. He proposed that perception leaves physical traces—what he called "residues" (enkataleimmata)—in our sensory organs. Think of them as biological recordings.

Here's how he thought it worked:

1. Perception Creates a Residue: When you see a white horse, the visual experience creates a physical change in your sensory system—a "residue" that encodes the perceptual information (the horse's whiteness, shape, movement).

2. The Residue Persists: This residue doesn't disappear when the horse trots away. It remains in your sensory apparatus, preserving the content of what you perceived.

Here's what makes residues special: they don't just tell your brain 'you saw a horse'—they preserve the specific details of WHAT you saw. The particular shade of white, the height, the movement. It's the preservation of these specific details that enables you to mentally 'see' the horse again later, rather than just know abstractly that you saw one.

3. The Residue Enables Mental Imagery: Later, this preserved residue can trigger your phantasia (imagination capacity), creating a quasi-perceptual experience—you "see" the horse in your mind's eye, even though no horse is present.

According to Alexander, this is why you can remember, imagine, and dream: you're reactivating preserved sensory residues.

The Aphantasia Connection: What Happens When There Are No Residues?

Alexander assumed this residue system was universal—that everyone's perceptions left these traces that could be reactivated as mental images. His entire theory of memory, imagination, and dreaming depends on it.

But aphantasia proves this assumption wrong.

If Alexander's theory describes the neurological mechanism underlying typical mental imagery (and modern neuroscience suggests something similar does happen in visualizers' brains), then aphantasics might be described as having one or both of these differences:

Residues aren't created in the same way, or

Residues can't be reactivated to produce conscious imagery

In Alexander's framework, without these reactivatable residues, you literally couldn't form mental images—which is exactly what aphantasics report.

What About Dreams and Errors?

In the ideal case, residues faithfully preserve perceptual content—when you accurately remember the white horse, your residue has maintained all the original information intact. The phantasia triggered by this residue will be true to the original perception.

But Alexander recognized that residues can degrade over time or lose information, leading to errors. He proposed two mechanisms that explain how phantasia can be distorted or false—why you might dream about purple elephants or misremember your friend wearing a red shirt when it was blue:

Impressing Further (prosanatypoun): When a residue loses information over time (becomes incomplete), your phantasia "fills in the gaps" with content from other stored residues. This explains why you might remember the horse as black when it was actually white—the specific color information degraded, and your mind supplied a plausible replacement.

Picturing (anazōgraphēsis): A special process that creates composite images from fragments of different residues. This explains dreams about people you've never met or creatures that don't exist (like Pegasus, Alexander's example). Your mind cobbles together features from various stored residues to create novel combinations.

Here's the crucial difference in how picturing works: When you directly perceive a horse, your perception is about that specific horse in front of you—philosophers call this de re awareness ("this thing I'm perceiving right now"). But when picturing creates mental imagery from degraded residues, it identifies the subject through a mental description ("the white four-legged animal," "the snub-nosed man").

This descriptive identification is fallible in ways direct perception isn't—you might mentally "picture" the wrong individual, confuse similar-looking people, or even create images of things that don't exist, like winged horses.

This explains several types of mental imagery errors:

Misidentification: You dream about "the tall bearded man" and think it's your uncle, but the description could fit multiple people.

Hallucination: Your mind pictures "the threatening figure in the corner" when nothing is there.

Imagining non-existents: You visualize Pegasus by combining "horse" + "wings" from separate residues.

For aphantasics, the absence of these mechanisms might explain not just the lack of voluntary mental imagery, but also:

Why many aphantasics report not dreaming visually (or not remembering visual dreams).

Why aphantasics rely on semantic or factual memory—without these "creative" error mechanisms, memories might be less prone to reality distortion.

Why aphantasics think in concepts, facts, or spatial relationships rather than sensory simulations.

The Conceptual Thinker Alternative

Alexander's contemporary critics might have asked: "But surely people can think about horses without seeing mental images?"

Actually, Alexander had an answer—though he didn't realize its full significance. He acknowledged that some mental processes work differently. When you see someone wearing white and recognize them as 'Diares' son,' you're not relying on mental imagery alone—you're using conceptual knowledge (understanding what "son" means) and factual memory (knowing who Diares is). These mental operations don't require reactivating visual residues at all. They work through meaning and relationships rather than sensory simulation.

This hints at an alternative mode of thinking that doesn't require reactivating sensory residues: conceptual or propositional thinking.

Visualizers think: [mental image of a white horse]

Aphantasics think: "horse" + "white" + spatial/conceptual relationships

Alexander assumed the first mode was necessary for all mental representation. Aphantasia proves you can think richly and effectively using the second mode alone.

Why This Matters Today

Alexander's work is more than historical curiosity—it provides a sophisticated framework for understanding exactly what differs between aphantasic and typical minds:

1. Validates the Difference: Alexander's assumption that everyone has reactivatable sensory residues shows this isn't a modern bias. For millennia, thinkers assumed mental imagery was universal because it was universal in their experience.

2. Explains the Mechanism: Modern neuroscience is discovering that something like Alexander's "residues" really exists—patterns of neural activation that can be replayed. Understanding the theory helps aphantasics grasp what's supposedly happening in visualizers' brains.

3. Highlights Cognitive Diversity: By showing what aphantasics don't do, we better appreciate what they do do—think in alternative, often more abstract ways.

4. Historical Continuity: From Aristotle's phantasia to Alexander's residues; Francis Galton's 1880 Breakfast Study discovering "non-imagers" to Adam Zeman's 2015 coining of "aphantasia"—this is one continuous story of slowly recognizing that minds work differently.

The Irony of Alexander's Legacy

There's something wonderfully ironic about Alexander of Aphrodisias' contribution to understanding aphantasia.

He came from Aphrodisias (modern-day Turkey), a city whose name derives from Aphrodite, Greek goddess of love and beauty—things typically associated with rich sensory experience and visualization.

Yet by meticulously documenting the mechanism he thought everyone shared, Alexander created a perfect blueprint for understanding how aphantasic minds work differently. He showed us the biological "machinery" that visualizers use—and in doing so, revealed that this machinery isn't actually universal.

For 1,800 years, his theory stood as evidence that mental imagery was fundamental to human thought. Today, with aphantasia recognized in 1-5% of the population, this growing body of research stands as evidence of cognitive diversity—proof that brilliant, complex thinking doesn't require the sensory residues he described.

Connecting Ancient Philosophy to Modern Discovery

The journey from Aristotle to Alexander to modern aphantasia research reveals something profound: the questions haven't changed, only our ability to answer them.

340 BC - Aristotle: Defined phantasia as the capacity for mental imagery.

200 AD - Alexander: Explained the mechanism through preserved sensory residues.

1880 - Francis Galton: Discovered some people lack vivid mental imagery.

2015 - Adam Zeman: Named aphantasia and confirmed it affects 1-5% of people.

2020s - Current research: Using brain imaging to understand the neural differences.

Each generation has grappled with the same mystery: how do we think about what we cannot see? Alexander's answer—through reactivated sensory traces—describes one way. Aphantasia proves there's another.

What do you think? Does Alexander's "residue" theory help you understand what's different about aphantasic minds? Leave a comment below.