In his ‘Troubles with Functionalism’, Block develops his now-famous Homunculi-Head thought experiment. At one point (p.292), he claims that there are psychological differences between a person and their Homunculi-Headed simulation, but I don’t get what psychological differences Block has in mind. To develop this question, let me first summarise Block’s thought experiment.

According to (one version of) functionalism, there is a Turing machine T that I realise. Imagine a being, Blocky, that also realises T, but in a radically different way: Blocky’s body is an exact duplicate of mine; but instead of the brain, there is a control centre, in which little men perform certain, simple tasks. Collectively, they make sure that Blocky realises T: if Blocky is in state s and receives input i; and if T’s table requires output o and transition into state s+; then there’s a little man who sets o in motion and makes the transition to s+ happen. (o could be a wince, while ‘the transition to s+’ means letting the others know the system in now in s+.)
Although Blocky is a functional duplicate of me, he isn’t a mental duplicate (says Bock): when Blocky and I have our fingers pricked, we both wince; but only I experience pain. Blocky experiences nothing: he has no qualia, and there’s nothing it is like to be Blocky.
Conclusion: if being functionally identical doesn’t entail being mentally identical, then mental states (esp. qualia) couldn’t be functional states.

I get the argument, and I also get (and share) the intuition that Blocky doesn’t experience any qualia. Later in the paper, however, Block makes the claim I don’t get:

Homunculi-Heads like Blocky “are not things to which neurophysiological theories true of us apply, and if they are construed as Functional (rather than Psychofunctional) simulations, they need not be things to which psychological (information-processing) theories true of us apply.” (p.292, italics in original)

Neurophysiological theories that are true of us don’t apply to Blocky, because such theories describe what’s happening in our brains. Since Blocky doesn’t have a brain, these theories are false of Blocky. At first, I thought that psychological theories that are true of us don’t apply to Blocky because of statements like (A).

(A) He winced in response to the electric shock because the shock hurt him.

This is true of me (let’s say) but false of Blocky, because it refers to a quale (the shock hurt), which is absent in Blocky. Yet (A) can’t be what Block has in mind: the fact that different psychological theories apply to Blocky and me is supposed to support the intuition that Blocky doesn’t have any qualia. So, we can’t rely on the absence of qualia to show that Blocky and I are psychologically different.
Block seems to think that there’s a difference there, only if we consider folk-psychological theories. (That’s what ‘construed as Functional rather than Psychofunctional’ is about.) At the same time, he keeps putting ‘information-processing’ after ‘psychological’ – which sounds more like scientific, cognitive psychology.

So, my question is: what (folk-)psychological differences does Block see between me and my Homunculi-Headed simulation?

  • A scan of this paper showed he does follow somewhat Dennet’s ‘string of consciousness’ (which is based on Cartesian duality) he calls ‘Cartesian Theater’. An observant station functioning (much like a homunculi) as a narrative reporter of the world we are immersed into. There are relativity issues in any homunculi and multi mind theory of consciousness. Dennet is looking at function based on Decartes’ methodology and Block is proposing functionalism as some form of alchemy, with a host of possible psychological data points correlating to the mind as a predicate for action. You have choices Commented Jun 9, 2018 at 4:07
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    The mistake Block seems to make is to assume that Blocky will wince. Why would he do this if he has no qualia? The idea appears to be absurd. It would be easier to say that because Blocky does not wince we can assume he has no qualia. If we say Blocky will wince despite not feeling the pain then we have muddled the issues beyond recovery. How would we explain this wincing?
    – user20253
    Commented Jun 13, 2018 at 10:10
  • Wouldn’t we explain the wince simply through the functional equivalence? That’s the output the system gives when receiving a prick in the finger as input. Even a zombie (who is behaviourally equivalent to us by definition) will wince, although she has no qualia.
    – MarkOxford
    Commented Jun 13, 2018 at 11:06
  • @Mark Oxford: Have you come across this essay by Chomsky, The Case against B.F. Skinner? You might find it intresting reading - it was a comprehensive debunking of the whole notion of behaviourlism. Commented Jun 20, 2018 at 3:09
  • Here's a tasty little titbit from it:"As to its social implications, Skinner’s science of human behavior, being quite vacuous, is as congenial to the libertarian as to the fascist...there is little doubt that a theory of human malleability might be put to the service of totalitarian doctrine." Commented Jun 20, 2018 at 3:12

1 Answer 1



In 'Troubles with Functionalism', Block introduces functionalism as a "new incarnation of behaviorism" where "sensory inputs and mental states" produce a "disposition to act and have certain mental states" (262). The functionalist seeks an ontological reduction of mental states to functional states viz. functional descriptions of their logical relations grounded1 in physical (sensory) inputs and (e.g. behavioral) outputs. Such functional states could be modeled in terms of logical sentences like Ramsey functional correlates, or as parts of dynamic (state) models or computational systems like Turing machines. An actual machine (or nonmachine) which implements such states, sensory inputs and behaviors (outputs) can be said to realize2 the corresponding model.

Block distinguishes two methods of reduction: Functionalism, where inputs, outputs and states correspond to common-sense or folk-psychological theory, and Psychofunctionalism where inputs, outputs and states correspond to scientific psychological theory (allowing e.g. neural activations as an input or output) (268-9). The quote on p. 292 occurs in a context where Block has just contrasted two types of homunculi: one composed of subatomic aliens scientifically indistinguishable from an ordinary human (realizing a Psychofunctional model of brain activity), and one whose inner workings (perhaps fleas, tiny men, or a Turing machine) are empirically completely unlike an ordinary human (Blocky, realizing a Functional model of human behavior). Here we can regard the Functional simulation as one that fulfills a reduction of folk-psychological states and behaviors, and the Psychofunctional simulation as one that fulfills a reduction of neurological states and interactions.

Troubles with Blocky

Block implies that a Functionalist should accept ex hypothesi that Blocky has Functional states and therefore (folk-psychological) mental states identical to a human. However, there is room for disagreement. As a simple example, if Blocky were constructed to simulate person A, A may know themselves to have a genuine psychology including a genuine quale for pain. However, they may have reasonable doubt as to whether Blocky has the same quale or even any qualia at all. If we follow a Kripkean notion of identity we can then trivially conclude that it's not necessary that Blocky has the same mental state.

In another instance, Block gives an example of an intermittent paralytic on page 297. Consider a different (not Block's) intermittent paralytic Mitty with a neurological condition which often prevents him from drinking water or realizing that he is incapable of doing so. Mitty in one instance desires to drink a glass of water and believes himself capable of doing so. But a paradigmatic Functional interpretation of believing oneself capable of drinking water and desiring to drink water may be to typically result in drinking water. However, if Mitty typically fails to drink water, a corresponding Blocky under that paradigmatic Functional interpretation would not be ascribed the functional state of both believing oneself capable of drinking water and desiring to drink water. Arguably, this corresponds to a difference in information-processing between Mitty and Blocky3.

Shoemaker suggests for the case of paralytics etc., considering a "paradigmatically embodied person," which Block claims to be a retreat from Functionalism to Psychofunctionalism (298-9). It seems we can infer that Block would say that in terms of information-processing, a Functional Blocky is not necessarily the same as the corresponding human (Mitty). The case is different for information processing in the context of a Psychofunctional homunculus, not based on folk-psychology. There we might exchange the terms of belief and desire for empirical expressions in an appropriate scientific psychological theory. Following Block, it seems plausible to accept ex hypothesi that such a simulation would necessarily have the same empirical psychology (information-processing) as a human.

Mental Differences and the Argument against Functionalism

The quote from p. 292 seems to suggest a coherent argument against Functionalism. In the first part, things like Blocky "are not things to which neurophysiological theories true of us apply." Most relevant here is that if humans are A, and Blocky B, that from a neurophysiological perspective A and B are completely different. So, if you think that neurophysiology is relevant to mental properties, you should expect that from a mental perspective A does not equal B.

"They need not be things to which psychological (information-processing) theories true of us apply," appears to be a modal claim. We can express this as saying that from an information-processing perspective it is not necessary that B is equivalent to A.

Here, we can simplify and formalize the argument to show how one would argue for mental differences and how to use those differences to argue against Functionalism. For convenience, we'll refer to the following contexts: neurophysiologically (N), information-processing (I), qualia (Q), mentally (M), and functionally (F). We'll also include a human A, and Blocky B and use modal logic operators [] and <> for necessary and possible respectively.

Given a _Functional_ Blocky, we obtain some simplified statements from the quote: 1. (N) A =/= B 2. (I) ~[] (B = A) And transform them a bit 2a. (I) <> ~(A = B) Since properties of A are fixed 2b. <> Exists B s.t. (I) ~(A = B) 2c. <> Exists B s.t. (I) (A =/= B) But if we take such a B to be theoretically plausible, and as the B under consideration then 2d. (I) (A =/= B) So we have 3. (N, I) (A =/= B) Meaning that neurophysiologically, and from an information-processing standpoint, humans are not equivalent to Blocky. Block elsewhere supports the intuition that there's a corresponding absence of or difference in qualia. *3a. (Q) (A =/= B) or (B has no qualia) Although it doesn't necessarily follow, Block thinks it's reasonable that we have intuitions that Q, N and I are relevant to mental state. If so, perhaps we can conclude: *3b. (M) (A =/= B)

Alternatively, *3a as (B has no qualia) can satisfy the premise AQ of the Absent Qualia Argument (AQA)

From _intuition_, _prima facie_ AQ. (<> Exists B, B has no qualia) But since (presumably) mentality requires qualia *3b. (M) (A =/= B)

With *3b we can make the argument against Functionalism:

We introduced Blocky as Functionally equivalent to A 4. (F) A = B But if we want to use functionalism as a reductive theory of mind, then we'd expect mental equivalence to be implied by functional equivalence. We'd say that *5. for all X, Y (F) X = Y -> (M) X = Y **or** for all X, Y (F) X = Y <-> (M) X = Y so for A and B we can say 5b. (F) A = B -> (M) A = B But if we believe *3b, then 6. (F) A = B and (M) A =/= B So if *3b is reasonable, we should deny *5.

Block's distinction between Functional and Psychofunctional simulations alongside his phrasing of "psychological (information-processing) theories" appears to emphasize e.g. neuroscientific theories of how we process information. This seems to correspond to how Blocky's internal logic is not the same as the logic realized inside a human brain.

In response, a functionalist (perhaps Psychofunctionalist) like Shoemaker would accept the AQA but deny *3a and so deny *3b. An eliminativist could accept AQ and *3a but deny that *3b follows. Block seems to think AQ, *3a and *3b are all reasonable.

1 See symbol grounding problem. Block describes this as "'tacking down' mental states only at the periphery." (284)

2 Realization is a standard term for an implementation of a computational model (e.g. a Turing machine) or other input/output system in mathematical or computational logic. See also Realization (systems), and p. 306 for an example for Block's use regarding nonmachines.

3 To expand a bit on this, one common folk-psychological theory that seems suitable for a Functional law relates belief, desire and action. We might say the desire to φ along with the belief that one can φ, typically results in doing φ. So a paradigmatic Functional interpretation of belief and desire would be belief that can φ + desire to φ -> typically does φ. We'll call this Functional law belief+desire->action. Since Blocky is a simulation of Mitty, Blocky typically fails to drink water. Yet since Blocky is a Functional simulation he follows Functional laws and has corresponding mental states. But because of belief+desire->action, Blocky to be a Functional simulation must lack either the desire to drink water, or the belief that he is capable of drinking water. If Mitty doesn't drink because he can't while Blocky doesn't drink because he either doesn't desire to or doesn't believe that he can, this seems to correspond to a difference in information-processing between Mitty and Blocky.

This further seems to suggest a difference in mental states between Mitty and Blocky. A Functionalist could respond that Mitty doesn't actually have belief+desire for drinking water. But that seems to disagree with common-sense psychology. Alternatively, one could deny belief+desire->action. But we are left with a similar problem for any mental state that can't be expressed in a paradigmatic Functional way.

  • Thanks! You suggest that the quote “isn’t intended to show that Blocky doesn’t have qualia”, but I’m not sure. Block wants to back the intuition that Blocky has no qualia, and he seems to think that (possible) psychological differences are the way to do it: “since [Blocky] need not be anything like you psychologically […] it is reasonable to doubt that it has mentality”. (296) “there is good reason to take seriously our intuition that [Blocky has] no mentality. The good reason is that […he] need not have […] psychological (information-processing) […] mechanisms anything like ours”. (301)
    – MarkOxford
    Commented Jun 12, 2018 at 10:26
  • I appreciate this is a modal claim/argument: Block says ‘need not have’ the same psychology, rather than ‘doesn’t have’. I’d still like to understand how Blocky’s psychology could differ from mine. In other words, I’d like to know more about the second premise in your argument: if the (P, I)-standpoint accepts ~[] (B = A), that standpoint presumably acknowledges a situation/world where A and B in fact differ. I’d like to know what that situation looks like (according to (P, I)).
    – MarkOxford
    Commented Jun 12, 2018 at 10:28
  • @Mark Block certainly wants to back the intuition that Blocky has no qualia, but he makes that argument elsewhere. I think you are confusing mentality (mental states) for qualia (phenomenal experience). In my breakdown, psychological (P) differences like differences in qualia are a premise for this portion of argument. The hopeful conclusion establishing mental (M) differences *3b, is what Block would be supporting on 296, and 301. If we take (I) to be differences in e.g. belief and desire, Blocky w/ trained fleas we expect to satisfy (P, I) A =/= B (differing qualia, belief, desire).
    – Greg S
    Commented Jun 13, 2018 at 2:12
  • If “differences in qualia are a premise for this portion of argument”, isn’t the argument trivial? If Blocky lacks qualia, of course he and I are different mentally (but functionally the same) – simply because qualia are a kind of mental state. (Perhaps you don’t think they are?) Won’t the Functionalist try to reject the premise that there are “differences in qualia” between Blocky and me? It seems to me that that’s the claim Block needs to (and is trying to) support. Once we grant there are “differences in qualia”, the conclusion that there are mental differences seems far less contentious.
    – MarkOxford
    Commented Jun 13, 2018 at 10:05
  • @Mark Block supports the prima facie argument from intuition that (<> Exists B, B doesn't have qualia) and so *3b (AQA). He continues this, e.g. by claiming that (I) ~[] (A = B) supports the intuition. But the given quote presents an argument roughly following the more formal structure I gave (excluding (P)sychologically). Functionalists (except eliminativists) are likely to deny absence (and maybe difference) in qualia; per Shoemaker (cf. Functionalism and Qualia) absent or differing qualia are sufficient for *3b, but Block I think is rightly unconvinced regarding the latter.
    – Greg S
    Commented Jun 14, 2018 at 7:56

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