Infinite Minds, A Philosophical Cosmology, John Leslie, Oxford University Press, 2001,
ISBN 0-19-924892-3
Leslie’s new book supplies some bold answers to some big questions. The position he
develops is an interesting one; although there is much that is speculative, the speculation
is not groundless, but is invariably supported by argument, even if not all of the
arguments are as polished or as precise as one might like. Leslie is well aware that his
cosmology will strike many contemporary readers as bizarre, but this does not mean that
it is wrong, or should be ignored. Even if it is wrong, it might well be wrong for
interesting reasons, and in locating these reasons, we will be learning something about
what the ultimate options might be.
1. Axiarchism
For some, ‘Why is there anything rather than nothing?’ is the ultimate philosophical
question, and they may be right. But there is a second question, scarcely less deep and
difficult: ‘Why is reality the way it is?’ A completed physics might conceivably supply
an answer to the ‘Why this?’ question, for it is not inconceivable that the laws of nature
might be such as to necessitate the existence of the physical reality the laws themselves
govern – if only in the sense that the laws cannot become actual independently of the
reality to which they apply. But even if such laws did exist, the ‘Why anything?’
question would remain unanswered. Why has this possibility been actualized? Why has
any possibility been actualized?
Some say: ‘There is no answer; it is just a brute fact that a universe like this one
exists.’ For those unwilling to swallow an unexplained datum of this magnitude, one
option is to follow Lewis, and hold that all possible worlds have the same status, all are
equally real. But although this manoeuvre neatly sidesteps the problem of explaining
why only one of the infinitely numerous possible universes is actual, many feel the
original ‘Why Anything?” problem remains unsolved; indeed, aren’t we now being asked
to accept a far larger and more complex brute fact? Traditional theism provides another
solution: God exists, and God chose to create this (rather than any other) universe. But as
is well known, this option is also problematic, even if we assume God exists. Why did
God create this universe (which, as is plain, is not without its flaws)? Why does God
himself exist? Is the notion of a being that is responsible for its own existence, or which
could not fail but to exist, really intelligible?
There is at least one further option, vigorously championed by Leslie in his Value
and Existence (1979), and now again in Infinite Minds, an option which can be traced
back as far as Plato: perhaps the universe exists because it is ethically required to exist.
On this view – ‘Extreme Axiarchism’ [EA] – of all the possible ways the universe could
be, one is better than the rest; this possible universe actually exists, and it exists precisely
because it is the best: truths about value are ‘creatively effective’.
EA’s solution to the ‘Why Anything?’ problem can initially strike one as strange.
If goodness is creatively effective, there is precious little evidence of this in day to day
life; the good things that do happen (and we could do with there being more of them)
usually seem to have more mundane explanations: the decisions people take,
conjunctions of circumstance and physical laws. But even if the creative power of the
good is never discernible in our surroundings (and some might question this), it does not
mean that the universe as a whole might not owe its existence to this creative power.
Moreover, as ultimate explanations go, and as Leslie takes pains to point out, EA has
definite advantages. It is simpler than traditional theism, since a single creative principle
explains both why there is something rather than nothing, and why this something takes
the form it does. And if God does exists, the Axiarchist can explain why: it is simply
because a universe which includes God has greater value than one which does not.
Leslie does not claim that EA is true. He defends the weaker claim that EA might
be true, that it is a conceptually coherent ultimate explanation. And he may well be right.
Certainly – as Leslie (repeatedly) points out – there are influential philosophers, Mackie
and Parfit amongst them, who think that he is.
But for all its advantages, I cannot see that EA entirely avoids the problem of the
unexplained brute fact, for one such is still being posited, namely the existence of
creatively effective objective value. This brute fact may have the unusual property of
being able to explain everything else, but it is a brute fact nonetheless. Indeed, it may
well be that there are several ultimate and unexplained posits involved, not one. Leslie
notes that the ‘concepts of ethically required existence and of existence required with
causal or creative success truly are two concepts, not one. So far as mere concepts are
concerned, absolutely any ethical requirement might fail to be fulfilled.’ (161) So on the
one hand, certain possibilities have the property of being ethically required to exist, and
on the other, certain possibilities possess the property of self-actualization (they are such
that they come into being). It so happens that all the self-actualizing possibilities are
ethically required. But why? Leslie argues that this is no coincidence. He maintains that
it is a non-logical, non-analytic, but nonetheless necessary truth that ethical needs possess
creative power. Even if we grant that such necessities exist, isn’t the existence of this
particular necessity, as opposed to the conceivable alternatives, something which needs
explaining? If so, then given that no explanation is forthcoming, we have yet another
unexplained posit. Axiarchism may be a coherent doctrine, but it is not as simple and
straightforward as it initially seems.
2. Cosmology
If EA were true, what would the universe be like? Evidently, it would be better than any
other possible universe. But can we go further? From the hypothesis that our universe is
the best possible, can we deduce anything of interest about its nature? Leslie is of the
opinion that we probably can, and Infinite Minds is largely devoted to the metaphysical
implications of EA. While a good many of the ideas Leslie discusses were first
introduced in Value and Existence, they did not feature prominently; in the newer work
they are developed in considerably more detail.
All the essentials of Leslie’s cosmology are determined by a few basic
assumptions, none of which is absurd or implausible. Let us suppose, as many do, that
only states of consciousness possesses intrinsic value. Are all forms of consciousness of
equal intrinsic value? This seems unlikely. Leslie argues that only unified states of
consciousness can possess intrinsic value, and that richer, more complex, forms of
consciousness have greater value than simpler forms (given certain provisos about their
contents). From this it follows that a maximally unified and maximally complex
conscious mind will have greater intrinsic value than anything else. Are there any limits
on how rich and complex a mind can be? Leslie thinks not: a maximally complex mind
will be infinitely complex. Consequently, if EA is true, an infinite mind will not merely
be possible, it will actually exist. Since this infinite mind is also maximally good, Leslie
sees no objection to regarding it as God-like, or divine, and generally refers to it as ‘the
divine mind’.
For this conclusion to be believable, there are questions which require plausible
answers. What is the relationship between the divine mind and the world we are familiar
with from everyday life? If the actual universe is the best possible universe, why is it so
easy to imagine universes which seem clearly to be better than the actual universe,
universes which contain more beauty and less pointless suffering than our own?
Leslie’s solution to the relationship question is a Spinoza-style pantheism. The
divine mind does not contemplate anything external to it, everything it thinks about is
realized (i.e. becomes actual) in it. Your consciousness and mine exist as tiny regions
within the infinitely rich divine consciousness. As for non-conscious physical things,
such as tables or bricks, Leslie suggests they exist merely as ‘structures’ within the divine
mind, a position which is entirely compatible with what science tells us about the
physical world, since the latter provides us only with causal-structural knowledge (it is
silent about the intrinsic qualitative nature of material things). Quite what these
structures are, however, is left unclear. Are they blue-print like images, or are they more
akin to fully detailed conceptualizations? On occasion Leslie also displays sympathies
with those panpsychists who hold that even the simplest material things possess a
rudimentary form of consciousness. If this view is correct, material things would have
the same status within the divine mind as ourselves (or at least, our streams of
consciousness).
While pantheism certainly provides the simplest answer to the relationship
question, it promises to make the problem of evil harder to solve. If there are no limits to
what the divine mind knows, and if a state of affairs becomes real simply by being
entertained by the divine mind, won’t all possible states of affairs be actualized? Some
of the resulting universes will be vastly superior to this one, but others will be vastly
inferior. We are no longer faced merely with the problem of explaining why this
universe is as bad as it is, we are faced with the likelihood of an infinite number of
universes existing which are all far worse than this one. How can this depressing
prospect be reconciled with EA?
Leslie solves both problems with a single move. A divine mind does indeed, he
suggests, contemplate an infinite number of possible universes, all of which are thereby
actualized, but it does not contemplate all possible universes, it contemplates only those
that are ‘worth thinking about’. The universes that are worth thinking about contain
conscious lives that are generally (if not always or in every individual case) worth living,
even if these lives contain a mixture of the good, bad and the indifferent – as is the case
in our world. Those possible universes where most lives are not worth living are not
worth contemplating, and so are not actualized.
While there is no denying that this is an appealingly simple solution to the
problem of evil, the notion that a divine mind might be selective in what it knows or
contemplates may well seem dubious. How is it possible to decide not to think certain
thoughts without first being aware of the content of these thoughts? How could a divine
mind avoid actualizing those worlds it decides are not worth thinking about? But this
objection draws its force from a conception of the divine mind as an intelligent agent
whose cognitive processes are similar to our own. Leslie’s divine mind is more akin to a
single timeless state of consciousness, one that is forced into existence by virtue of its
supreme value. The idea that an experiential complex of this kind could include some,
but not all, possible experiences is by no means absurd.
Leslie extends his solution to the problem of evil to the problem of induction. He
suggests that among the worlds that are not worth thinking about are those where the
laws of nature suddenly vary (or vanish) after long periods of stability. I am not so sure.
Can we be confident that worlds with variable laws are invariably not worth living in? If
there were occasional (or even frequent) exceptions to the laws in our universe, would the
consequences on conscious beings necessarily be catastrophic? Evidence has recently
emerged that the ‘fine tuning constant’ may well have had a different value in the distant
past; if it did, the speed of light or the charge on electrons must also have been different –
our universe might in fact have variable laws of nature.
Leslie also speculates that the divine mind might well find it worth considering
how mental lives might continue to unfold after our bodily deaths: ‘cutting short a happy
life is surely somewhat ugly at the very least’ (128). If so, an afterlife is something we
can reasonably hope for, we may even have a right to one – the divine mind will be under
something akin to a duty to sustain us in being. Our bodies will die, but our streams of
consciousness will continue on in a dimension ‘orthogonal’ to that of ordinary spacetime,
where we might join with other survivors, ‘sharing with them in an adventure of
discovering even more about the marvels of divine knowledge’ (129). And the same
might apply to other, more primitive animals, such as lions or frogs, provided they
sometimes have lives worth living.
The prospect of ‘continuing on’ in the fashion Leslie describes is not an
unwelcome one, but again, I have my doubts. Does death always involve the cutting
short of a life worth living? Is it not possible to live in such a way that death, when it
comes, constitutes a not unwelcome completion to a life well-rounded and well-lived? In
any event, there is something else that Leslie has not taken into account. In a manyuniverse model such as his own, an afterlife (of a kind) is inevitable, without the need for
the sort of ‘extensions’ he hopes we may have. For do not forget, in a cosmos of this sort
there is a very real sense in which each one of us is a multitude. For we each have
counterparts in an infinite number of other universes; the lives of our counterparts are
indistinguishable from our own for a while, and then diverge. So if you suffer the
misfortune of being run over by a bus tomorrow, you have an infinite number of
counterparts who will not take the fatal step, who will go on living their lives, in their
increasingly different ways, for years to come. Some of these counterparts will live
forever, for in their universes – where the laws of nature may be subtly different from our
own – the secret of eternal life is discovered during their lifetimes. These counterparts of
yours will lead every kind of life you could wish for; you may not live to visit the stars,
but you have counterparts who do. ‘But these counterparts would not be me!’, you might
object. But in the context of Leslie’s system, this objection has less than its usual force.
You are not an individual substance, but merely a pattern of experience within a divine
mind, a pattern whose many variants are exhaustively explored elsewhere in the same
mind. The relationship between the experiences in your mental life and those in the lives
of your counterparts is of a particularly intimate kind: they all belong to the same mental
subject.
Although Leslie generally writes of ‘the divine mind’, this is merely to keep
things simple. He believes that if one divine mind exists solely because it should, it is
likely that more than one exists; indeed he argues that it is more probable than not that an
infinite number of divine minds exists. Of course, as every sweet-eating child learns,
more of a good thing isn’t always better. But since minds do not compete for the same
space, there is no limit to the number that can co-exist, even if each is infinitely rich and
complex. It could even be that each of these minds is exactly similar. This would not be
possible if indiscernibles were identical, but Leslie argues that there is no reason to
suppose this need be the case.
There is more to Leslie’s cosmology than I can usefully mention here. The Btheory of view of time is defended in chapter 3, and a version of compatibilism is
explored in chapter 4, along with much else. I turn instead to examine, in some detail, an
issue which is central to the system as a whole, and upon which all else hangs.
3. Unity
Leslie’s second chapter, ‘Minds Human, Artificial and Divine’ is by far the longest in the
book. The arguments here are complex, convoluted, at times exasperating, and range
over topics as diverse as the nature and unity of consciousness (divine and human),
machine mentality, Bradley on relations, quantum entanglement and quantum
computation. I will focus on the main strand: the character of experiential unity, and the
relationship between our minds and the divine mind of which they are a part.
Like everything else in our universe, your consciousness and mine are constituent
parts of a single divine mind. Despite its infinite complexity a divine mind is also
unified: ‘divine thoughts form a whole supremely worth experiencing’ (43). As is
obvious, there is tension here. If your experiences and mine are experienced together in a
single conscious mind, why is it that our consciousnesses seem so completely separate?
As William James put the point, ‘no thought ever comes into direct sight of a thought in
another personal consciousness.’ To address this question at all we need to know more
about the kind of unity to be found in an individual consciousness, and the kind of unity
to be found in divine minds.
Consider first the unity of our own consciousness at a given time. Our typical
states of consciousness consist of a number of different experiences, but these
experiences are not mere collections, they occur together in a distinctive way: they are
experienced together, they are co-conscious, as one might say. It may be impossible to
describe this mode of unity in an informative manner, but we nonetheless know what it is
like for a visual experience to be co-conscious with an auditory experience, or for distinct
visual experiences to be co-conscious with one another (e.g. seeing several points of light
at once against a dark backdrop). Every part of a typical state of consciousness is, it
seems, co-conscious with every other part. Or as Leslie puts it: ‘introspection indicates
that conscious experiences can be wholes of a dramatically unified kind, wholes whose
wholeness is grasped by the wholes themselves’ (79).
Call this distinctive and dramatic experiential togetherness ‘phenomenal unity’.
Leslie devotes a good deal of attention to the topic, and most of what he says is
interesting and plausible. He notes that phenomenal unity extends a short way over time,
which explains ‘why states of awareness seem to cover brief temporal intervals, as when
musical notes played in swift succession appear to be experienced together’ (81). He
even ventures the claim that phenomenal unity might ‘explain’ the qualitative character
of experiences (72-6), which may be true, at least in the sense that there couldn’t be
anything that it is like to have an experience of a certain expanse of colour (say), unless
the constituent parts of the expanse are mutually co-conscious. But on one point Leslie
does goes astray.
We are told that phenomenally unified experiences are ‘not separate in their
being’, they have ‘identities that are partially fused’. Although the latter notion is not
clearly explained (or defended), it is not implausible to suppose that co-conscious
experiences are holistically related, in such a way that the constituent parts of
phenomenally unified wholes could not exist in different experiential configurations.
For one could reasonably hold that when two experiences are co-conscious they are so
intimately linked that a complete description of the phenomenal character of either would
include a description of the phenomenal character of the other. If so, then given certain
other plausible assumptions (e.g. that the identity of an experience depends upon its
complete phenomenal character, its time of occurrence, and its subject), the conclusion
swiftly follows that experiences in phenomenally unified wholes could not exist on their
own, or in wholes of a different overall character. But note, this sort of inter-experiential
interdependence, rooted as it is in inter-experiential relations, does not posit (or require)
any interdependence or interpenetration at the level of intrinsic (or local) phenomenal
character. This is just as well, for there is no reason to think that the intrinsic or local
character of an experience is (typically) affected by the other experiences with which it is
co-conscious. When I look at the tree outside my window, the purely visual aspects of
this experience are generally the same irrespective of whether they are co-conscious with
the sound of a birdcall, or the sound of a passing car, or no sound at all. If there is a
sense in which the identity of the visual tree-experience depends upon the other
experiences with which it is co-conscious, there is also a sense in which it is not.
Now, on various occasions Leslie argues that even if a classical computer could
reproduce the kind of information processing that goes on in our brains, such a computer
would never be conscious, since its physical constituents, scattered as they are through
space, clearly do not possess the special kind of unity that our experiences possess.
However, he suggests that quantum computers might be different, on the grounds that
when particles enter certain quantum states (e.g. Bose-Einstein condensates) they almost
entirely lose their individualities, they cease to be separate entities. As a consequence, it
may well be that quantum states of this kind have the properties needed for a physical
correlate of phenomenally unified states. But in the light of what has just been said, this
seems quite wrong. While there is a sense in which experiences in phenomenal wholes
are interdependent, such experiences clearly do not lose their individuality in the manner
of the particles entering the Bose-Einstein condensates. In an audio-visual experience,
the auditory and visual elements remain clearly distinct, rather than being submerged into
some entirely new, non-auditory and non-visual, experience.
But let us return to the main theme. What is the relationship between our states of
consciousness and the divine mind? Are the experiences which compose the divine
consciousness unified in the same way as our experiences? This is very hard to believe.
Could my current state of consciousness have the character it actually has if all of its
constituent experiences were fully co-conscious not only with your experiences, but with
each and every other experience in the divine mind? Trying to argue that this is possible
would be an intriguing exercise, but Leslie makes no such attempt, he willingly accepts
that our states of consciousness have a higher degree of unity than the divine mind itself,
taken as a whole: ‘Inside any greater unity possessed by our universe in its entirety there
are complex systems whose elements are still more thoroughly unified: unified in ways
fundamental to any intrinsically worthwhile experiences of ours. Knowledge of our own
conscious states shows us that they are instances of such systems …’ (70) While this
concession does seem plausible, it leaves us with a problem: in what way are the
experiences in a divine mind unified?
One possibility, which Leslie mentions but does not explore in detail, is
overlapping chains of co-consciousness. It seems natural to think that synchronic coconsciousness is a transitive relation, that if a first experience is co-conscious with a
second, and the second is co-conscious with a third, then the first and the third
experiences will also be co-conscious. But perhaps – as Michael Lockwood has argued –
co-consciousness is not transitive. If so, and as Leslie points out, then experiences A-BC-D could form a unified whole, as could experiences C-D-E-F, with these two wholes
partially overlapping in the C-D region. However, even if experiential structures of this
sort are possible, which is by no means clear, it is hard to see how this mechanism could
unify all the experiences in a divine mind. What are the experiential intermediaries
linking your current experiences to mine? No plausible candidates spring to mind. There
is a further option, one which Leslie does not mention. If the co-consciousness relation
were non-symmetrical, it would be possible for a collection of experiences A-B-C (e.g.
your current state of consciousness) to be co-conscious with experiences D-E-F (e.g.
other parts of the divine consciousness) without any of the latter being co-conscious with
any of the former. But although this option meets Leslie’s needs, it is also highly
implausible. Since experiences related by co-consciousness are experienced together – in
effect, they are fused into a single state of consciousness – how could co-consciousness
fail to be symmetrical? Co-consciousness, in this guise at least, is necessarily
symmetrical.
In fact, Leslie carefully avoids committing himself to the claim that a divine
consciousness is a phenomenally unified whole. What he does claim is that divine minds
are ‘unified in their existence’. The parts or properties of a thing are unified in their
existence if (like the length and redness of a brick) they are incapable of existing on their
own; parts of this sort are ‘merely abstract’, in the sense that they are merely aspects of a
more fundamental reality, one which is capable of independent existence.
If a divine consciousness is unified in its existence, it is undeniably a single entity.
But a question remains to be answered: what is it, precisely, which binds the constituents
of a divine consciousness together? Although Leslie supplies an answer, he spends little
time developing it. The proposed solution is a form of telepathic linkage: ‘even a mind
or mental region which had never been, say, fearful, could know what fear was like ‘as if
telepathically’, its knowledge then coming very close to being knowledge of exactly what
it’s like to feel fear … So I have little difficulty with the idea of a divine overview of our
entire universe – a state of extraordinarily detailed knowledge appreciated as a single
whole’ (105). Since we are told nothing more about this mode of ‘as-if telepathic’
awareness, it is difficult to evaluate Leslie’s proposal. Nonetheless, I foresee problems
and complications.
Leslie does not say as much, but it seems fair to assume that the telepathically
linked experiences are existentially unified in virtue of the fact that they are so linked. It
is not implausible to suppose this would be the case. After all, we can make sense of the
distinction between genuine and hallucinatory telepathic experiences; the former, but not
the latter, provide the telepath with direct knowledge of another subject’s experience, and
so could not exist in the absence of the ‘target’ experience. So far so good. But a
problem remains. Even if we assume that telepathic links of the required sort do exist, it
is by no means clear that collections of experiences linked in this way have the sort of
unity that is required for them to belong to the same mind. Telepathy, as usually
construed, is a relationship between distinct minds. Consequently, since it seems the
divine overview is a complex experience in its own right, wouldn’t it constitute a distinct
conscious mind in its own right?
This problem may not be insoluble. Perhaps it would suffice to construe the
telepathic link along the lines of a direct realist view of ordinary perception (though
Leslie elsewhere rejects the pure structureless apprehending that this view seems to
require, cf. 13-14); perhaps other options are available. In any event, let us suppose that a
divine overview of all our individual consciousnesses does exist, as Leslie supposes.
Why stop here? Might there not be less encompassing overviews, taking in rather less
than the complete picture? Surely there would be, since these lesser overviews would
still be experiences worth having, and so – given EA – experiences that would exist.
There may well be an infinite number of these less encompassing overviews. By the
same reasoning, perhaps too there would be overviews of the overviews – why not? – and
these too might be infinite in number. But it does not end here. Leslie, it will be
recalled, believes it likely that there would be an infinite number of divine minds, not just
one. If so, then surely – given his own assumptions about the intrinsic value of unified
experiences – there would be an overview of this multiplicity: an overview of an infinite
number of infinitely complex minds. Perhaps it doesn’t end here. Just as there could be
lesser overviews of a single divine mind, there could be less encompassing overviews of
the multiplicity of minds. And, as before, there might also be overviews of these
overviews – the process might be iterated indefinitely. Nor need it end here. What is to
prevent entire complexes, of the sort just outlined, being instantiated more than once?
But if multiple complexes exist, won’t there also exist overviews of these complexes? I
will not go further, for the point is already clear: Leslie’s cosmos may be somewhat more
complex than he himself appreciates.
One last point. As already noted, although Leslie does not hold that the
experiences within a divine mind must be phenomenally unified, he does maintain that
they must be unified in their existence. He also claims that any state of mind that is
intrinsically worth experiencing must be unified in its existence. The latter claim is, I
suspect, problematic; so much so that I doubt whether his cosmology can survive the
blow, at least in its original form.
Our states of consciousness are unified in their existence – or so Leslie alleges,
and he may well be right. But in addition, our states of consciousness also possess a
distinctive form of unity – phenomenal unity – a form of unity that is not possessed by
other types of existentially unified whole. The colour and length of a brick may be
existentially unified, but they are not phenomenally unified. Given this, we can ask:
which mode of unity is relevant to the intrinsic value that our states of consciousness
possess? The answer, surely, is phenomenal unity. As Leslie himself argues, it is
phenomenal unity which is responsible for experiences having the character they do. The
fact that the constituent parts of an experiential whole could not exist in isolation is, in
itself, irrelevant to the value of that experience. Experiential parts are existentially
unified because they are phenomenally unified, and it is the latter mode of unity which,
along with their intrinsic qualitative character, provides them with any value they might
have.
If so, and if a divine mind forms a whole that is ‘supremely worth experiencing’,
then it is hard to see how the experiences which jointly constitute a divine mind could fail
to be phenomenally unified. Mere unity in existence would not suffice, for this mode of
unity, in itself, is irrelevant to the value of an experience. And since it is difficult to see
how distinct ‘personal consciousnesses’, such as yours and mine, can be phenomenally
unified with one another, it may well be that divine minds, in the form Leslie envisages,
simply could not exist in the framework of EA. Perhaps the cosmos consists of
multitudes of phenomenally unified consciousnesses of the sort we possess, some
simpler, some far more complex. Axiarchism may lead us back to Leibniz, rather than
Spinoza.
Barry Dainton
Department of Philosophy
The University of Liverpool