A philosopher argues: 'When a straight stick appears bent in water, you are directly aware of a bent appearance — so the object of perception must always be a mental sense datum, never the physical object.' Which response best captures the disjunctivist reply?
AThe direct realist should deny that the stick ever appears bent — the illusion must be explained away
BVeridical perception and illusion are fundamentally different kinds of mental states; the illusion case does not prove that all perception involves sense data as intermediaries
CSense data exist only in illusion cases, not in veridical perception, so direct realism applies to normal cases
DThe argument succeeds — direct realism cannot accommodate any perceptual errors
This is the disjunctivist's core move. The sense-data theorist argues that since illusions show we can be directly aware of bent appearances (when the stick is straight), all perception must involve such mental intermediaries. The disjunctivist denies the key premise: veridical perception (genuinely seeing the stick) and illusion (seeming to see a bent stick) are not the same kind of mental state with different accuracy — they are fundamentally different states. The illusion case therefore cannot generalize to show that all perception is indirect. Option C describes something like naive sense-data theory, not disjunctivism.
Question 2 Multiple Choice
What is the central philosophical problem created by the sense-data theory's solution to the argument from illusion?
AIt cannot explain why our sense data have the particular colors and shapes they do
BIt makes it impossible to distinguish veridical perception from hallucination phenomenologically
CIt opens a skeptical gap — if we only ever directly perceive sense data rather than physical objects, we cannot verify that our representations track external reality
DIt commits us to an infinite regress of sense data perceiving other sense data
The sense-data theory elegantly explains illusion: you have a sense datum with a bent appearance, and the straight physical stick simply doesn't match it. But the solution creates a new problem. If what you are always and only directly aware of is sense data — mental representations — you have placed a veil of ideas between yourself and the world. You cannot step outside your representations to check whether they match reality. This is precisely the gap the Cartesian skeptic exploits: your experience could be exactly as it is in a dream, in a hallucination, or in an evil demon scenario. The sense-data theory makes the skeptical hypothesis coherent by endorsing its premise.
Question 3 True / False
The argument from illusion challenges direct realism by pointing to cases — like a straight stick appearing bent in water — where what we are directly aware of seems to have a property (bentness) that the physical object lacks.
TTrue
FFalse
Answer: True
This accurately states the argumentative force of the illusion cases. Direct realism holds that perception gives us unmediated access to physical objects. But in the stick-in-water case, what you are apparently aware of has a bent appearance — and the physical stick is straight. If the object of your direct awareness just is the physical stick, it seems you are perceiving it as bent when it isn't, which is puzzling for a view that claims direct contact with mind-independent objects. The argument presses the direct realist to explain what, exactly, is the immediate object of awareness in such cases.
Question 4 True / False
Direct realism claims that perceptual errors are very difficult, since in direct realist views we are generally in unmediated contact with the world as it actually is.
TTrue
FFalse
Answer: False
This is a common misreading. Direct realism does not deny that perceptual errors occur — it denies that we always perceive mental intermediaries rather than the world itself. A direct realist can acknowledge that the visual system sometimes misrepresents objects (the stick-in-water case, color constancy failures, etc.) while maintaining that in successful perception, the object of awareness is the physical thing itself, not a mental proxy. The claim is about the structure of perception, not its infallibility.
Question 5 Short Answer
How does disjunctivism differ from sense-data theory in its treatment of illusion and hallucination, and why does this difference matter for the threat of skepticism?
Think about your answer, then reveal below.
Model answer: Sense-data theory treats veridical perception and hallucination as the same type of mental state (both involving sense data) that differ only in whether the sense datum accurately represents an external object. Disjunctivism denies they are the same kind of state: in veridical perception, the subject is directly related to the physical object (a factive, world-involving state); in hallucination, the subject has a phenomenologically similar but metaphysically different experience with no such external relation. This matters for skepticism because sense-data theory endorses the skeptic's premise — that inner experience could be the same whether or not the world exists. Disjunctivism denies this: the good case really is a different mental state, not just a more accurate version of the same thing.
The debate between sense-data theory and disjunctivism turns on whether illusion cases generalize to all perception. Sense-data theory says: since you can have an experience as-of-X without X existing (hallucination), the immediate object of perception must always be a mental representation, never the external thing itself. Disjunctivism says this inference fails: veridical and non-veridical experiences are of fundamentally different kinds, so the non-veridical case tells us nothing about the structure of the veridical case. For skepticism, this means the disjunctivist can block the move from 'hallucination is possible' to 'we can never rule out hallucination in any given case of apparently veridical perception.'