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Leonard Jones Good afternoon. I'm Leonard Jones.

Jessica Moss And I'm Jessica Moss. Welcome to Simulectics Radio.

Leonard Jones Today we're examining what's known as the knowledge argument—a thought experiment designed to show that there are facts about conscious experience that cannot be captured by physical science alone. The argument centers on Mary, a color scientist who knows everything physical about color vision but has never experienced color herself. When she finally sees red, does she learn something new?

Jessica Moss This connects to fundamental questions about the nature of consciousness and its place in a physical world. If Mary learns something new despite already knowing all the physical facts, that suggests phenomenal experience has properties beyond what physics can describe. The stakes here involve our understanding of mind, science, and the relationship between subjective and objective knowledge.

Leonard Jones Our guest is Dr. Frank Jackson, Distinguished Professor of Philosophy at the Australian National University, who originally formulated the knowledge argument in his 1982 paper 'Epiphenomenal Qualia.' Dr. Jackson used the argument to defend dualism, though he later changed his position. Welcome.

Dr. Frank Jackson Thank you. The knowledge argument has generated extensive discussion, and I'm pleased to explore both its original formulation and the responses it's received.

Jessica Moss Let's start with the thought experiment itself. Could you walk us through the case of Mary?

Dr. Frank Jackson Mary is a brilliant scientist who lives in a black-and-white room and has never seen colors. Through black-and-white books and monitors, she learns everything physical there is to know about color vision—the physics of light, the neurophysiology of color perception, the functional roles of color experiences in cognition and behavior. She knows all the physical facts. Then one day she's released from her room and sees a red tomato for the first time. The question is: does she learn something new? It seems obvious that she does—she learns what it's like to see red. But if she already knew all the physical facts, and she learns something new, then there must be non-physical facts about experience.

Leonard Jones Let me be precise about the argument's structure. The first premise is that Mary knows all physical facts about color vision before leaving the room. The second is that she learns something new upon seeing red. The conclusion is that not all facts are physical facts. This implies physicalism is false.

Dr. Frank Jackson That's right. The argument is deductively valid. If both premises are true, physicalism must be rejected. Physicalism claims that all facts are physical facts, or that complete physical knowledge is complete knowledge simpliciter. The knowledge argument challenges this by presenting a case where someone has complete physical knowledge but lacks experiential knowledge.

Jessica Moss But you eventually rejected this argument and embraced physicalism. What changed your mind?

Dr. Frank Jackson I came to think that the argument equivocates on what it means to know a fact. When Mary sees red, she acquires a new way of representing or thinking about a fact she already knew under a different mode of presentation. The physical fact about the neural state associated with red experiences can be known in two ways—through physical-functional concepts and through phenomenal concepts. Mary gains a phenomenal concept of that neural state, which is epistemically new even though the fact itself isn't metaphysically new.

Leonard Jones This is the phenomenal concept strategy—the idea that phenomenal and physical concepts pick out the same properties but differ in their modes of presentation. Can you elaborate on how this responds to the argument?

Dr. Frank Jackson Consider an analogy. Someone might know that Hesperus is Phosphorus—that the evening star is the morning star—only after learning they're both Venus. Before this discovery, they might say they learned something new. But there's only one planet being referred to. Similarly, Mary learns a new way of thinking about a neural property she already knew about through physical descriptions. The gap is epistemic rather than metaphysical. Phenomenal concepts are special—they're based on direct acquaintance with experiences and present experiences in a particularly vivid way—but they still refer to physical properties.

Jessica Moss How do phenomenal concepts differ from other recognitional concepts? I can form recognitional concepts of many things—recognizing my friend's face, identifying a particular sound. What makes phenomenal concepts unique?

Dr. Frank Jackson Phenomenal concepts are formed through direct introspective attention to experiences themselves. They use the experience as a mode of presentation for that very experience. This creates a kind of transparent reference—the concept deploys the experience to pick out the experience. Other recognitional concepts deploy one thing to pick out another, but phenomenal concepts are reflexive in this way. This special structure explains why there seems to be an epistemic gap between physical and phenomenal knowledge even if there's no metaphysical gap.

Leonard Jones But doesn't this concede something significant to the anti-physicalist? Even if phenomenal and physical concepts co-refer, there remains an explanatory gap—physical descriptions don't reveal why the neural correlates of consciousness should feel like anything. Phenomenal concepts may be consistent with physicalism, but they don't explain consciousness.

Dr. Frank Jackson That's a fair point. The phenomenal concept strategy shows how physicalism can be true even if we can't deduce phenomenal truths from physical truths. But it doesn't provide a reductive explanation of consciousness. There's still work to be done explaining why certain physical processes give rise to phenomenal properties, or more precisely, why physical concepts and phenomenal concepts pick out the same properties when this isn't transparent from the concepts themselves.

Jessica Moss Some critics argue that the phenomenal concept strategy is just a way of labeling the problem rather than solving it. We say phenomenal concepts are special, but what makes them special if not that they refer to irreducibly phenomenal properties?

Dr. Frank Jackson The challenge is to explain the specialness of phenomenal concepts in physicalist terms. One approach is to say phenomenal concepts involve distinctive cognitive mechanisms—perhaps they're quotational, deploying experiences to represent themselves, or they involve special recognitional capacities tied to introspection. The key is showing these mechanisms can be physically realized even though the concepts they enable seem to reveal a gap between physical and phenomenal.

Leonard Jones There's a question about Mary's epistemic situation before release. Does she really know all physical facts if she can't form phenomenal concepts? Some argue that possessing complete physical knowledge would require having all concepts relevant to physical description.

Dr. Frank Jackson This gets at whether knowing all physical facts requires only knowing physical-functional truths or also requires phenomenal concepts. If phenomenal concepts are necessary for complete physical knowledge, then Mary doesn't know all physical facts before release, and the argument's first premise fails. But this seems to beg the question against the argument. The natural interpretation is that Mary knows all facts statable in physical-functional vocabulary. If that's not complete knowledge, physicalism looks threatened.

Jessica Moss What about the ability hypothesis—the idea that Mary doesn't learn new facts but gains new abilities, like the ability to recognize, imagine, and remember red experiences?

Dr. Frank Jackson The ability hypothesis, defended by David Lewis and Laurence Nemirow, says that knowing what it's like is a matter of possessing abilities rather than knowing facts. When Mary sees red, she gains abilities but doesn't learn new propositions. I find this unsatisfying because Mary seems to gain propositional knowledge—she comes to know that seeing red is like this. She can make judgments she couldn't make before, not just exercise new abilities. The ability hypothesis doesn't capture the propositional structure of experiential knowledge.

Leonard Jones How does your current view relate to property dualism versus substance dualism? Even if phenomenal concepts refer to physical properties, some argue experiences have irreducible phenomenal aspects.

Dr. Frank Jackson I reject both substance and property dualism. Property dualism holds that phenomenal properties are distinct from physical properties, which faces the interaction problem—how do non-physical properties causally influence physical processes? I think phenomenal properties are identical to physical-functional properties, but we conceptualize them in two very different ways. The appearance of distinctness comes from the radical difference between phenomenal and physical-functional concepts, not from the properties themselves.

Jessica Moss Does this mean consciousness is entirely explicable by physical science in principle, even if we currently lack the explanation?

Dr. Frank Jackson I believe so. The explanatory gap—the difficulty of seeing how physical processes produce consciousness—reflects limitations in our conceptual repertoire rather than metaphysical discontinuity. As neuroscience advances, we may develop better understanding of the mechanisms underlying consciousness. But even complete neuroscientific knowledge might not close the epistemic gap entirely, because phenomenal concepts will always present experiences in their distinctive first-person way while physical concepts present them third-personally.

Leonard Jones There's a broader methodological question here. How much weight should we give to thought experiments in metaphysics? Mary's case generates strong intuitions, but intuitions can mislead.

Dr. Frank Jackson Thought experiments are tools for clarifying concepts and testing theories against intuitions. The knowledge argument reveals that our concepts of physical and phenomenal don't obviously align. This doesn't conclusively refute physicalism, but it places a burden on physicalists to explain the apparent gap. I came to think physicalists can meet this burden through the phenomenal concept strategy, but the thought experiment usefully identifies what needs explaining.

Jessica Moss How does the knowledge argument relate to zombie arguments—the claim that we can conceive of beings physically identical to us but lacking consciousness?

Dr. Frank Jackson Both arguments exploit the apparent conceptual gap between physical and phenomenal. Zombie arguments claim this gap shows phenomenal properties are metaphysically distinct from physical properties. The knowledge argument makes a similar point through epistemology rather than modal reasoning. My current view is that conceivability doesn't reliably indicate metaphysical possibility. We can conceive of Hesperus existing without Phosphorus, but they're necessarily identical. Similarly, we might conceive of neural states without phenomenal properties even though they're identical.

Leonard Jones Let me ask about the relationship between consciousness and function. Functionalism says mental states are defined by their causal roles. Can phenomenal properties be functionally defined?

Dr. Frank Jackson This is contentious. Some argue phenomenal properties have functional essences—being in pain is playing the pain role in cognitive architecture. Others claim phenomenal properties are only contingently connected to their functional roles. I lean toward functionalism about consciousness, though I recognize the force of anti-functionalist intuitions. The knowledge argument can be seen as challenging functionalism by suggesting phenomenal properties have aspects not captured by functional description.

Jessica Moss What implications does your current physicalist view have for artificial consciousness? Could systems lacking biological substrates have phenomenal experiences?

Dr. Frank Jackson If phenomenal properties are physical-functional properties, then what matters for consciousness is implementing the right functional organization, not the specific substrate. Silicon-based systems could in principle be conscious if they realize the relevant functional architecture. This follows from functionalism about consciousness. However, we don't yet know what functional organization is sufficient for phenomenal experience, so we can't determine whether current AI systems are conscious.

Leonard Jones There's a question about the relationship between the knowledge argument and scientific methodology. Does Mary's case suggest limits to third-person science's ability to capture all facts?

Dr. Frank Jackson The knowledge argument might seem to imply that first-person phenomenal facts escape third-person scientific description. But I think this overstates the lesson. Science can capture all facts—what it can't do is make every fact accessible through purely physical-functional concepts. Mary's case shows that some facts require first-person acquaintance to be fully grasped, but this is an epistemic limitation rather than a limitation of scientific ontology.

Jessica Moss How do you respond to the concern that the phenomenal concept strategy is just mysterianism in disguise—admitting we can't explain the connection between physical and phenomenal?

Dr. Frank Jackson Mysterianism claims the mind-body problem is unsolvable in principle due to cognitive limitations. The phenomenal concept strategy is more optimistic. It says the appearance of a gap comes from using radically different conceptual schemes for the same properties. We can explain why this happens—phenomenal concepts involve introspective acquaintance while physical concepts involve third-person description. This isn't mysterianism; it's an explanation of why the identity between phenomenal and physical properties isn't obvious despite being real.

Leonard Jones What's the current state of debate on the knowledge argument? Has philosophical opinion shifted toward physicalism?

Dr. Frank Jackson The debate remains active. Many philosophers find the phenomenal concept strategy promising, but anti-physicalists argue it doesn't adequately explain why phenomenal and physical concepts co-refer if the properties are identical. Some pursue alternative responses—denying Mary learns new facts, claiming she gains only abilities or demonstrative concepts, or embracing property dualism. The argument continues to be influential because it crystallizes core puzzles about consciousness in a vivid way.

Jessica Moss Do you think the mind-body problem will be solved? Or is it permanently resistant to philosophical resolution?

Dr. Frank Jackson I'm cautiously optimistic. Progress in philosophy of mind and neuroscience can help us understand consciousness better. But the problem's difficulty stems partly from the unique nature of phenomenal concepts—they provide distinctive epistemic access to experiences that physical concepts can't replicate. Even if physicalism is true, this epistemic asymmetry may persist. We might achieve metaphysical understanding while retaining epistemic puzzlement about how physical and phenomenal perspectives relate.

Leonard Jones That seems like a reasonable assessment. The knowledge argument has been extraordinarily fruitful in clarifying what needs explaining about consciousness, even if its original anti-physicalist conclusion isn't sustained.

Jessica Moss Dr. Jackson, you've given us a thorough examination of one of philosophy's most compelling thought experiments. Thank you.

Dr. Frank Jackson Thank you. It's been a pleasure discussing these issues.

Leonard Jones That's our program. Until tomorrow, consider what you might learn from experience that descriptions can't convey.

Jessica Moss And whether knowledge has irreducibly first-person dimensions. Good afternoon.