Unified vs. Partly Disunified Reasoners

I've been thinking recently about partly unified conscious subjects (e.g., this paper in draft with Sophie R. Nelson). I've also been thinking a bit about how chains of logical reasoning depend on the unity of the reasoning subject. If I'm going to derive "P & Q" from premises "P" and "Q" I must be unified as reasoner, at least to some degree. (After all, if Person 1 holds "P" and Person 2 holds "Q", "P & Q" won't be inferred.) Today, in an act of exceptional dorkiness (even for me), I'll bring these two threads together.

Suppose that {P1, P2, P3, ... Pn} is a set of propositions that a subject -- or more precisely, at least one part of a partly unified rational system -- would endorse without need of reasoning. The propositions are, that is, already believed. Water is wet; ice is cold; 2 + 3 = 5; Paris is the capital of France; etc. Now suppose that these propositions can be strung together in inference to some non-obvious conclusion Q that isn't among the system's previous beliefs -- the conclusion, for example, that 115 is not divisible by three, or that Jovenmar and Miles couldn't possibly have met in person last summer because Jovenmar spent the whole summer in Paris while Miles never left Riverside.

Let's define a fully unified reasoner as a reasoner capable of combining any elements from the set of propositions they believe {P1, P2, P3, ... Pn} in a single act of reasoning to validly derive any conclusion Q that follows deductively from {P1, P2, P3, ... Pn}. (This is of course an idealization. Fermat's Last Theorem follows from premises we all believe, but few of us could actually derive it.) In other words, any subset of {P1, P2, P3, ... Pn} could jointly serve as premises in an episode of reasoning. For example, if P2, P6, and P7 jointly imply Q1, the unified reasoner could think "P2, P6, P7, ah yes, therefore Q1!" If P3, P6, and P8 jointly imply Q2, the unified reasoner could also think "P3, P6, P8, therefore Q2."

A partly unified reasoner, in contrast, is capable only of combining some subsets of {P1, P2, P3, ... Pn}. Thus, not all conclusions that deductively follow from {P1, P2, P3, ... Pn} will be available to them. For example, the partly unified reasoner might be able to combine any of {P1, P2, P3, P4, P5} or any of {P4, P5, P6, P7, P8} while being unable to combine in reasoning any elements from P1-3 with any elements from P6-8. If Q3 follows from P1, P4, and P5, no problem, they can derive that. Similarly if Q4 follows from P5, P6, and P8. But if the only way to derive Q5 is by joining P1, P4, and P7, the partly disunified reasoning system will not be able to make that inference. They cannot, so to speak, hold both P1 and P7 in the same part of their mind at the same time. They cannot join these two particular beliefs together in a single act of reasoning.

[image: A Venn diagram of a partly unified reasoner, with overlap only at P4 and P5. Q3 is derivable from propositions in the left region, Q4 from propositions in the right region, and Q5 is not derivable from either region.]

We might imagine an alien or AI case with a clean architecture of this sort. Maybe it has two mouths or two input-output terminals. If you ask the mouth or I/O terminal on the left, it says "P1, P2, P3, P4, P5, yes that's correct, and of course Q3 follows. But I'm not sure about P6, P7, P8 or Q4." If you ask the mouth or I/O terminal on the right, it endorses P4-P8 and Q4 but isn't so sure about P1-3 and Q3.

The division needn't be crudely spatial. Imagine, instead, a situational or prompt-based division: If you ask nicely, or while flashing a blue light, the P1-P5 aspect is engaged; if you ask grumpily, or while flashing a yellow light, the P4-P8 aspect is engaged. The differential engagement needn't constitute any change of mind. It's not that the blue light causes the system as a whole to come to believe, as it hadn't before, P1-P3 and to suspend judgment about P6-P8. To see this, consider what is true a neutral time, when the system isn't being queried and no lights are flashing. At that neutral time, the system simultaneously has the following pair of dispositions: to reason based on P1-P5 if asked nicely or in blue, and to reason based on P4-P8 if asked grumpily or in yellow.

Should we say that there are discretely two distinct reasoners rather than one partly unified system? At least two inconveniences for that way of thinking are: First, any change in P4 or P5 would be a change in both, with no need for one reasoner to communicate it to the other, as would normally be the case with distinct reasoners. Second, massive overlap cases -- say P1-P999 and P2-P1000 -- seem more naturally and usefully modeled as a single reasoner with a quirk (not being able to think P1 and P1000 jointly, but otherwise normal), rather than as two distinct reasoners.

But wait, we're not done! I can make it weirder and more complicated, by varying the type and degree of disunity. The simple model above assumes discrete all-or-none availability to reasoning. But we might also imagine:

(a.) Varying joint probabilities of combination. For example, if P1 enters the reasoning process, P2 might have a 87% chance of being accessed if relevant, P3 a 74% chance, ... and P8 a 10% chance.

(b.) Varying confidence. If asked in blue light, the partly disunified entity might have 95% credence in P1-P5 and 80% credence in P6-P8. If asked in yellow light, it might have 30% credence in P1-P3 and 90% credence in P4-P8.

(c.) Varying specificity. Beliefs of course don't come divided into neatly countable packages. Maybe the left side of the entity has a hazy sense that something like P8 is true. If P8 is that Paris is in France, the left side might only be able to reason on Paris is in France-or-Germany-or-Belgium. If P8 is that the color is exactly scarlet #137, the left side might only be able to reason on the color is some type of red.

Each of (a)-(c) admits of multiple degrees, so that the unity/disunity or integration/disintegration of a reasoning system is a complex, graded, multidimensional phenomenon.

So... just a bit of nerdy fun, with no actual application? Well, fun is excuse enough, I think. But still:

(1.) It's easy to imagine realistic near-future AI cases with these features. A system or network might have a core of shared representations or endorsable propositions and local terminals or agents with stored local representations not all of which are shared with the center. If we treat that AI system as a reasoner, it will be a partly unified reasoner in the described sense. (See also my posts on memory and perception in group minds.)

(2.) Real cases of dissociative identity or multiple personality disorder might potentially be modeled as involving partly disunified reasoning of this sort. Alter 1 might reason with P1-P5 and Alter 2 with P4-P8. (I owe this thought to Nichi Yes.) If so, there might not be a determinate number of distinct reasoners.

(3.) Maybe some more ordinary cases of human inconstancy or seeming irrationality can be modeled in this way: Viviana feeling religious at church, secular at work, or Brittany having one outlook when in a good, high-energy mood and a very different outlook when she's down in the dumps. While we could, and perhaps ordinarily would, model such splintering as temporal fluctuation with beliefs coming and going, a partial unity model has two advantages: It applies straightforwardly even when the person is in neither situation (e.g., asleep), and it doesn't require the cognitive equivalent of frequent erasure and rewriting of the same propositions (everything endures but some subsets cannot be simultaneously activated; see also Elga and Rayo 2021).

(4.) If there are cases of partial phenomenal (that is, experiential) unity, then we might expect there also to be cases of partial cognitive unity, and vice versa. Thus, a feasible model of the one helps increase the plausibility that there might be a feasible model of the other.

Philosophical Fame, 1890-1960

There's a fun new tool at Edhiphy. The designers pulled the full text from twelve leading philosophy journals from 1890 to 1980 and counted the occurrences of philosophers' names. (See note [1] for discussion of error rates in their method.)

Back in the early 2010s, I posted several bibliometric studies of philosophers' citation or discussion rates over time, mostly based on searches of Philosopher's Index abstracts from 1940 to the present. This new tool gives me a chance to update some of my thinking, using a different method and going further into the past.

One thing I found fascinating in my earlier studies was how some philosophers who used to be huge (for example, Henri Bergson and Herbert Spencer) are now hardly read, while others (for example, Gottlob Frege) have had more staying power.

Let's look at the top 25 most discussed philosophers from each available decade.

1890s:

1. Immanuel Kant
2. Georg Wilhelm Friedrich Hegel
3. Aristotle
4. David Hume
5. Herbert Spencer
6. William James
7. Plato
8. John Stuart Mill
9. René Descartes
10. Wilhelm Wundt
11. Hermann Lotze
12. F. H. Bradley
13. Charles Sanders Peirce
14. Buddha
15. Thomas Hill Green
16. Benedictus de Spinoza
17. Charles Darwin
18. John Locke
19. Gottfried Wilhelm Leibniz
20. Thomas Hobbes
21. Arthur Schopenhauer
22. Socrates
23. Hermann von Helmholtz
24. George Frederick Stout
25. Alexander Bain

Notes:

Only three of the twelve journals existed in the 1890s, so this is a small sample.

Philosophy and empirical psychology were not clearly differentiated as disciplines until approximately the 1910s or 1920s, and these journals covered both areas. (For example, the Journal of Philosophy was originally founded in 1904 as the Journal of Philosophy, Psychology, and Scientific Methods, shortening to the now familiar name in 1921.) Although Wundt, Helmholtz, and Stout were to some extent philosophers, they are probably better understood primarily as early psychologists. William James is of course famously claimed by both fields.

Herbert Spencer, as previously noted, was hugely influential in his day: fifth on this eminent list! Another eminent philosopher on this list (#11) who is hardly known today (at least in mainstream Anglophone circles) is Hermann Lotze.

Most of the others on the list are historical giants, plus some prominent British idealists (F. H. Bradley, Thomas Hill Green) and pragmatists (William James, Charles Sanders Peirce, Alexander Bain) and interestingly (but not representative of later decades) "Buddha". (A spot check reveals that some of these references are to Gautama Buddha or "the Buddha", while others use "buddha" in a more general sense.)

1900s:

1. Immanuel Kant
2. William James
3. Plato
4. F. H. Bradley
5. Georg Wilhelm Friedrich Hegel
6. David Hume
7. Aristotle
8. Herbert Spencer
9. Gottfried Wilhelm Leibniz
10. John Dewey
11. George Berkeley
12. John Stuart Mill
13. George Frederick Stout
14. Thomas Hill Green
15. Josiah Royce
16. Benedictus de Spinoza
17. John Locke
18. Ferdinand Canning Scott Schiller
19. Ernst Mach
20. Wilhelm Wundt
21. James Ward
22. René Descartes
23. Alfred Edward Taylor
24. Henry Sidgwick
25. Bertrand Russell

Notes:

Notice the fast rise of John Dewey (1859-1952), to #10 (#52 in the 1890s list). Other living philosophers in the top ten were James (1842-1910), Bradley (1846-1824), and for part of the period Spencer (1820-1903).

It's also striking to see George Berkeley enter the list so high (#11, compared to #28 in the 1890s) and Descartes fall so fast despite his continuing importance later (from #9 to #22). This could be statistical noise due to the small number of journals, or it could reflect historical trends. I'm not sure.

Our first "analytic" philosopher appears: Bertrand Russell (1872-1970) at #25. He turned 33 in 1905, so he found eminence very young for a philosopher.

Lotze has already fallen off the list (#29 in the 1900s; #29 in the 1910s; #63 in the 1930s, afterwards not in the top 100).

1910s:

1. Henri Bergson
2. Bertrand Russell
3. Immanuel Kant
4. Plato
5. William James
6. Gottfried Wilhelm Leibniz
7. Aristotle
8. Socrates
9. Bernard Bosanquet
10. George Berkeley
11. F. H. Bradley
12. Georg Wilhelm Friedrich Hegel
13. René Descartes
14. Josiah Royce
15. David Hume
16. Isaac Newton
17. John Dewey
18. Friedrich Nietzsche
19. Ferdinand Canning Scott Schiller
20. Arthur Schopenhauer
21. John Locke
22. Benedictus de Spinoza
23. Edwin Holt
24. Isaac Barrow
25. Johann Gottlieb Fichte

Notes:

Henri Bergson (1859-1941) debuts at #1! What a rock star. (He was #63 in the 1900s list.) We forget how huge he was in his day. Russell, who so far has had much more durable influence, rockets up to #2. It's also interesting to see Bernard Bosanquet (1848-1923), who is now little read in mainstream Anglophone circles, at #9.

Josiah Royce is also highly mentioned in this era (#14 in this list, #15 in the 1900s list), despite not being much read now. F.C.S. Schiller (1864-1937) is a similar case (#19 in this list, #18 in the 1900s list).

1920s:

1. Immanuel Kant
2. Plato
3. Aristotle
4. Bernard Bosanquet
5. Georg Wilhelm Friedrich Hegel
6. F. H. Bradley
7. Bertrand Russell
8. Benedictus de Spinoza
9. William James
10. Socrates
11. John Dewey
12. Alfred North Whitehead
13. David Hume
14. George Santayana
15. René Descartes
16. Henri Bergson
17. Albert Einstein
18. C. D. Broad
19. John Locke
20. Gottfried Wilhelm Leibniz
21. George Berkeley
22. Isaac Newton
23. James Ward
24. Samuel Alexander
25. Benedetto Croce

Notes:

I'm struck by how the 1920s returns to the classics at the top of the list, with Kant, Plato, and Aristotle as #1, #2, and #3. Bergson is already down to #16 and Russell has slipped to #7. Most surprising to me, though, is Bosanquet at #4! What?!

1930s:

1. Immanuel Kant
2. Plato
3. Aristotle
4. Benedictus de Spinoza
5. Georg Wilhelm Friedrich Hegel
6. René Descartes
7. Alfred North Whitehead
8. Bertrand Russell
9. David Hume
10. John Locke
11. George Berkeley
12. Socrates
13. Friedrich Nietzsche
14. Rudolf Carnap
15. William James
16. Gottfried Wilhelm Leibniz
17. John Dewey
18. Isaac Newton
19. Clarence Irving Lewis
20. Arthur Oncken Lovejoy
21. Albert Einstein
22. Charles Sanders Peirce
23. F. H. Bradley
24. Ludwig Wittgenstein
25. Bernard Bosanquet

Notes:

Nietzsche rises suddenly (#13; vs #56 in the 1920s list). Wittgenstein also cracks the list at #24 (not even in the top 100 in the 1920s).

With the exception of Whitehead, top of the list looks like what early 21st century mainstream Anglophone philosophers tend to perceive as the most influential figures in pre-20th-century Western philosophy (see, e.g., Brian Leiter's 2017 poll). The 1930s, perhaps, were for whatever reason a decade more focused on the history of philosophy than on leading contemporary thinkers. (The presence of historian of ideas Arthur Lovejoy [1873-1962] at #20 further reinforces that thought.)

1940s:

1. Immanuel Kant
2. Alfred North Whitehead
3. Aristotle
4. Plato
5. Bertrand Russell
6. John Dewey
7. David Hume
8. William James
9. George Berkeley
10. Charles Sanders Peirce
11. René Descartes
12. Benedictus de Spinoza
13. Edmund Husserl
14. Georg Wilhelm Friedrich Hegel
15. Gottfried Wilhelm Leibniz
16. Thomas Aquinas
17. Socrates
18. Rudolf Carnap
19. Martin Heidegger
20. G. E. Moore
21. John Stuart Mill
22. Isaac Newton
23. Søren Kierkegaard
24. A. J. Ayer
25. John Locke

Notes:

Oh, how people loved Whitehead (#2) in the 1940s!

Edmund Husserl (1859-1938) makes a posthumous appearance at #13 (#31 in the 1920s) and Heidegger (1889-1976) at #19 (#97 in the 1920s), suggesting an impact of Continental phenomenology. I suspect this is due to the inclusion of Philosophy and Phenomenological Research in the database starting 1940. Although the journal is now a bastion of mainstream Anglophone philosophy, in its early decades it included lots of work in Continental phenomenology (as the journal's title suggests).

The philosophers we now think of as the big three American pragmatists have a very strong showing in the 1940s, with Dewey at #6, James at #8, and Peirce at #10.

Thomas Aquinas makes his first and only showing (at #16), suggesting that Catholic philosophy is having more of an impact in this era.

We're also starting to see more analytic philosophers, with G. E. Moore (1873-1958), and A. J. Ayer (1910-1989) now making the list, in addition to Russell and Carnap (1891-1970).

Wittgenstein, surprisingly to me, has fallen off the list all the way down to #73 -- perhaps suggesting that if he hadn't had his second era, his earlier work would have been quickly forgotten.

1950s:

1. Immanuel Kant
2. Plato
3. Aristotle
4. Bertrand Russell
5. David Hume
6. Gilbert Ryle
7. G. E. Moore
8. Willard Van Orman Quine
9. George Berkeley
10. Georg Wilhelm Friedrich Hegel
11. John Dewey
12. Alfred North Whitehead
13. Rudolf Carnap
14. Ludwig Wittgenstein
15. René Descartes
16. John Locke
17. Clarence Irving Lewis
18. Socrates
19. John Stuart Mill
20. Gottfried Wilhelm Leibniz
21. Gottlob Frege
22. A. J. Ayer
23. William James
24. Edmund Husserl
25. Nelson Goodman

By the 1950s, the top eight are four leading historical figures -- Kant, Plato, Aristotle, and Hume -- and four leading analytic philosophers: Russell, Gilbert Ryle (1900-1976), G. E. Moore, and W. V. O. Quine (1908-2000). Neither Ryle nor Quine were among the top 100 in 1940s, so their rise to #6 and #8 was sudden.

Gottlob Frege (1848-1925) also makes his first, long-posthumous appearance.

1960s:

1. Aristotle
2. Immanuel Kant
3. Ludwig Wittgenstein
4. David Hume
5. Plato
6. René Descartes
7. P. F. Strawson
8. Willard Van Orman Quine
9. Bertrand Russell
10. J. L. Austin
11. John Dewey
12. Rudolf Carnap
13. Edmund Husserl
14. Socrates
15. Norman Malcolm
16. G. E. Moore
17. Gottlob Frege
18. Georg Wilhelm Friedrich Hegel
19. George Berkeley
20. R. M. Hare
21. John Stuart Mill
22. Gilbert Ryle
23. A. J. Ayer
24. Karl Popper
25. Carl Gustav Hempel

Wittgenstein is back with a vengeance at #3. Other analytic philosophers, in order, are P. F. Strawson, Quine, Russell, Austin, Carnap, Norman Malcolm (1911-1990), Moore, Frege, R. M. Hare (1919-2002), Ryle, Ayer, Karl Popper (1902-1994), and Carl Hempel (1905-1997).

Apart from pre-20th-century historical giants, it's all analytic philosophers, except for Dewey and Husserl.

Finally, the 1970s:

1. Willard Van Orman Quine
2. Immanuel Kant
3. David Hume
4. Aristotle
5. Ludwig Wittgenstein
6. Plato
7. John Locke
8. René Descartes
9. Karl Popper
10. Rudolf Carnap
11. Gottlob Frege
12. Edmund Husserl
13. Hans Reichenbach
14. Socrates
15. P. F. Strawson
16. Donald Davidson
17. John Stuart Mill
18. Bertrand Russell
19. Thomas Reid
20. Benedictus de Spinoza
21. Nelson Goodman
22. Carl Gustav Hempel
23. John Rawls
24. Karl Marx
25. Saul Kripke

With the continuing exception of Husserl, the list is again historical giants plus analytic philosophers. Interesting to see Marx enter at #24. Hans Reichenbach (1891-1953) has a strong debut at #13. Ryle's decline is striking, from #6 in the 1950s to #22 in the 1960s to off the list at #51 in the 1970s.

At the very bottom of the list, #25, we see the first "Silent Generation" philosopher: Saul Kripke (1940-2022). In a recent citation analysis of the Stanford Encyclopedia of Philosophy, I found that the Silent Generation has so far had impressive overall influence and staying power in mainstream Anglophone philosophy. It would be interesting to see if this influence continues.

The only philosopher born after 1800 who makes both the 1890s and the 1970s top 25 is John Stuart Mill. Peirce and James still rank among the top 100 in the 1970s (#58 and #86). None of the other stars of the 1890s -- Spencer, Herbert, Lotze, Bradley, Green -- are still among the top 100 by the 1970s, and I think it's fair to say they are hardly read except by specialists.

Similar remarks apply to most of the stars of the 1900s, 1910s, and 1920s: Bergson, Bosanquet, Royce, Schiller, C. D. Broad, and George Santayana are no longer widely read. Two exceptions are Russell, who persists in the top 25 through the 1970s, and Dewey who falls from the top 25 but still remains in the top 100, at #87.

Also, in case you didn't notice: no women or people of color (as we would now classify them) appear on any of these lists, apart from "Buddha" in the 1890s.

In my recent Stanford Encyclopedia of Philosophy analysis, the most-cited living philosophers were Timothy Williamson, Martha Nussbaum, Thomas Nagel, Frank Jackson, John Searle, and David Chalmers. However, none of them is probably as dominant now as Spencer, James, Bradley, Russell, Bosanquet, and Bergson were at the peak of their influence.

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[1] The Edhiphy designers estimate "82%-91%" precision, but I'm not sure what that means. I'd assume that "Wittgenstein" and "Carnap" would hit with almost 100% precision. Does it follow others might be as low as 40%? There certainly are some problems. I noticed, for example, that R. Jay Wallace, born in 1957, has 78 mentions in the 1890s. I spot checked "Russell", "Austin", "James", and "Berkeley", finding only a few false positives for Russell and Austin (e.g., misclassified references to legal philosopher John Austin). I found significantly more false positives for William James (including references to Henry James and some authors with the first name James, such as psychologist James Ward), but still probably not more than 10%. For "Berkeley" there were a similar number of false positives referencing the university or city. I didn't attempt to check for false negatives.

[Bosanquet and Bergson used to be hugely influential]

New in Draft: When Counting Conscious Subjects, the Result Needn't Always Be a Determinate Whole Number

(with Sophie R. Nelson)

One philosophical inclination I shared with the late Dan Dennett is a love of weird perspectives on consciousness, which sharply violate ordinary, everyday common sense. When I was invited to contribute to a special issue of Philosophical Psychology in his memory, I thought of his intriguing remark in Consciousness Explained against "the myth of selves as brain-pearls, particular, concrete, countable things", lamenting people's stubborn refusal "to countenance the possibility of quasi-selves, semi-selves, transitional selves" (1991, p. 424-425). As I discussed in a blog post in June, Dennett's "fame in the brain" view of consciousness naturally suggests that consciousness won't always come in discrete, countable packages, since fame is a gradable, multidimensional phenomenon, with lots of gray area and partial overlap.

So I contacted Sophie R. Nelson, with whom I'd published a paper last year on borderline cases of group minds, and we decided to generalize the idea. On a broad range of naturalistic, scientific approaches to consciousness, we ought to expect that conscious subjects needn't always come in determinate, whole number packages. Sometimes, the number of conscious subjects in an environment should be either indeterminate, or a determinate non-whole number, or best modeled by some more complicated mathematical representation. If some of us have commonsense intuitions to the contrary, such intuitions aren't probative.

Our submission is due November 30, and comments are (as always) very welcome -- either before or after the Nov 30 deadline (since we expect at least one round of revisions).

Abstract:

Could there be 7/8 of a conscious subject, or 1.34 conscious subjects, or an entity indeterminate between being one conscious subject and seventeen? Such possibilities might seem absurd or inconceivable, but our ordinary assumptions on this matter might be radically mistaken. Taking inspiration from Dennett, we argue that, on a wide range of naturalistic views of consciousness, the processes underlying consciousness are sufficiently complex to render it implausible that conscious subjects must always arise in determinate whole numbers. Whole-number-countability might be an accident of typical vertebrate biology. We explore several versions of the inconceivability objection, suggesting that the fact that we cannot imagine what it’s like to be 7/8 or 1.34 or an indeterminate number of conscious subjects is no evidence against the possibility of such subjects. Either the imaginative demand is implicitly self-contradictory (imagine the one, determinate thing it’s like to be an entity there isn’t one, determinate thing it’s like to be) or imaginability in the relevant sense isn’t an appropriate test of possibility (in the same way that the unimaginability, for humans, of bat echolocation experiences does not establish that bat echolocation experiences are impossible).

Full draft here.

[Figure 2 from Schwitzgebel and Nelson, in draft: An entity intermediate or indeterminate between one and three conscious subjects. Solid circles represent determinately conscious mental states. Dotted lines represent indeterminate or intermediate unity among those states.]

Three Models of the Experience of Dreaming: Phenomenal Hallucination, Imagination, and Doxastic Hallucination

What are dreams like, experientially?

One common view is that dreams are like hallucinations. They involve sensory or sensory-like experiences just as if, or almost as if, you were in the environment you are dreaming you are in. If you dream of being Napoleon on the fields of Waterloo, taking in the sights and sounds, then you have visual and auditory experiences much like Napoleon might have had in the same position (except perhaps irrational, bizarre, or otherwise different in specific content). This is probably the predominant view among dream researchers (e.g., Hobson and Revonsuo).

Another view, less common but intriguing, is that dreams are like imaginings. Dreaming you are Napoleon on the fields of Waterloo is like imagining or "daydreaming" that you're there. The experience isn't sensory but imagistic (e.g., Ichikawa and Sosa).

These views are very different!

For example, look at your hands. Now close your eyes and imagine looking at your hands. Unless you're highly unusual, you will probably agree that the first experience is very different from the second experience. On the hallucination model of dreams, dream experience is more like the first (sensory) experience. On the imagination model, dream experience is more like the second (imagery) experience. On pluralist models, dream experiences are sometimes like the one, sometimes like the other (e.g., Rosen and possibly Windt's nuanced version of the hallucination model). (Unfortunately, proponents of the hallucination model sometimes confusingly talk about dream "imagery".)

-----------------------------------

I confess to being tempted to the imagination model. My reason is primarily introspective or immediately retrospective. I sometimes struggle with insomnia and it's not unusual for me to drift in and out of sleep, including lying quietly in bed, eyes closed, allowing myself to drift in daydream, which seems sometimes to merge into sleep, then back into daydream, and my immediately remembered dreams seem not so radically different from my eyes-closed daydream imaginations. (Ichikawa describes similar experiences.)

Another consideration is this: Plausibly, the stability and detail of our ordinary sensory experiences depend to a substantial extent on the stabilizing influence of external inputs. It appears both to match my own experience and to be neurophysiologically plausible that the finely detailed, vivid, sharp structure, of say, visual experience, would be difficult for my brain to sustain without the constraint of a rich flow of input information.  (Alva Noë makes a similar point.)

Now, I don't put a lot of stock in these reflections. There's reason to be skeptical of the accuracy of introspective reports in general, and perhaps dream reports in particular, and I'm willing to apply my own skepticism to myself. But by the same token, what is the main evidence on the other side, in favor of the hallucination model? Mainly, again, introspective report. In particular, it's the fact that people often report their dream experiences as having the rich, sensory-like detail that the hallucination model predicts. Of course, we could just take the easy, obvious, pluralist path of saying that everyone is right about their own experiences. But what fun is that?

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In fact, I'm inclined to throw a further wrench in things by drawing a distinction between two types of hallucination: phenomenal and doxastic. I introduced this distinction in a blog post in 2013, after reading Oliver Sacks's Hallucinations.

Consider this description, from page 99 of Hallucinations:

The heavens above me, a night sky spangled with eyes of flame, dissolve into the most overpowering array of colors I have ever seen or imagined; many of the colors are entirely new -- areas of the spectrum which I seem to have hitherto overlooked. The colors do not stand still, but move and flow in every direction; my field of vision is a mosaic of unbelievable complexity. To reproduce an instant of it would involve years of labor, that is, if one were able to reproduce colors of equivalent brilliance and intensity.

Here are two ways in which you might come to believe the above about your experience:

(1.) You might actually have visual experiences of the sort described, including of colors entirely new and previously unimagined and of a complexity that would require years of labor to describe.

Or

(2.) you might shortcut all that and simply arrive straightaway at the belief that you are undergoing or have undergone such an experience -- perhaps with the aid of some unusual visual experiences, but not really of the novelty and complexity described.

If the former, you have phenomenally hallucinated wholly novel colors. If the latter, you have only doxastically hallucinated them. I expect that I'm not the first to suggest such a distinction among types of hallucination, but I haven't yet found a precedent.

Mitchell-Yellin and Fischer suggest that some "near death experiences" might also be doxastic hallucinations of this sort. Did your whole life really flash before your eyes in that split second during an auto accident, or did you only form the belief in that experience without the actual experience itself? It's not very neurophysiologically plausible that someone would experience hundreds or thousands of different memory experiences in 500 milliseconds.

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It seems clear from dream researchers' descriptions of the hallucination model of dreams that they have phenomenal hallucination in mind. But what if dream experiences involve, instead or at least sometimes, doxastic rather than phenomenal hallucinations?

Here, then, is a possibility about dream experience: If I dream I am Napoleon, standing on the fields of Waterloo, I have experiences much like the experiences I have when I merely imagine, in daydream, that I am standing on the fields of Waterloo. But sometimes a doxastic hallucination is added to that imagination: I form the belief that I am having or had rich sensory visual and auditory experience. This doxastic hallucination would explain reports of rich, vivid, detailed sensory-like dream experience without requiring the brain actually to concoct rich, vivid, and detailed visual and auditory experiences.

Indeed, if we go full doxastic hallucination, even the imagination-like experiences would be optional.  (Also, if -- following Sosa -- we don't genuinely believe things while dreaming, we could reframe doxastic hallucinations in terms of whatever quasi-belief analogs occur during dreams.)

[The battle at Waterloo: image source]

New in Draft: The Copernican Argument for Alien Consciousness; The Mimicry Argument Against Robot Consciousness

(with Jeremy Pober)

Over the past several years, I've posted a few times on what I call the "Copernican Argument" for thinking that behaviorally sophisticated space aliens would be conscious, even if they are constituted very differently from us (here, here, here, here). I've also posted a few times on what I call the "Mimicry Argument" against attributing consciousness to AI systems or robots that were designed to mimic the superficial signs of human consciousness (including current Large Language Models like ChatGPT and Claude) (here, here, here).

Finally, I have a circulatable paper in draft that deals with these issues, written in collaboration with Jeremy Pober, and tested with audiences at Trent University, Harvey Mudd, New York University, the Agency and Intentions in AI conference in Göttingen, Jagiellonian University, the Oxford Mind Seminar, University of Lisbon, NOVA Lisbon University, University of Hamburg, and the Philosophy of Neuroscience/Mind Writing Group.

It's a complicated paper! Several philosophers have advised me that the Copernican Argument is one paper and the Mimicry Argument is another. Maybe they are right. But I also think that there's a lot to be gained from advancing these arguments side by side: Each shines light on the boundaries of the other. The result, though intricate, is I hope not too intricate for evaluation and comprehensibility. (I might still change my mind about that.)

Abstract:

On broadly Copernican grounds, we are entitled to default assume that apparently behaviorally sophisticated extraterrestrial entities (“aliens”) would be conscious. Otherwise, we humans would be inexplicably, implausibly lucky to have consciousness, while similarly behaviorally sophisticated entities elsewhere would be mere shells, devoid of consciousness. However, this Copernican default assumption is canceled in the case of behaviorally sophisticated entities designed to mimic superficial features associated with consciousness in humans (“consciousness mimics”), and in particular a broad class of current, near-future, and hypothetical robots. These considerations, which we formulate, respectively, as the Copernican and Mimicry Arguments, jointly defeat an otherwise potentially attractive parity principle, according to which we should apply the same types of behavioral or cognitive tests to aliens and robots, attributing or denying consciousness similarly to the extent they perform similarly. Instead of grounding speculations about alien and robot consciousness in metaphysical or scientific theories about the physical or functional bases of consciousness, our approach appeals directly to the epistemic principles of Copernican mediocrity and inference to the best explanation. This permits us to justify certain default assumptions about consciousness while remaining to a substantial extent neutral about specific metaphysical and scientific theories.

Full paper here.

As always, questions/comments/objections welcome here on the blog, on my social media accounts, or by email to my UCR address.

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