Essentially this question asks how dualism can be introduced in Hard SF. The science-fictional answer is that provided the author of a dualistic Hard SF fiction introduced a form of dualism that follow a rigorous set of rules which are then applied consistently will constitute dualistic Hard SF. In this case, dualism is just another concept, that irrespective of its non-scientific origins, has taken and domesticated as science-fiction.
Other examples of non-scientific concepts domesticated as Hard SF include such obvious departures as vampires, supernatural creatures, psi-powers, various pseudosciences and other mythological entities. So it is not uncommon for science-fiction to import non-scientific to downright unscientific concepts and make them part of the field.
One example of dualistic hard SF is Bob Shaw's The Palace of Eternity (1969).
In The Palace of Eternity (1969) he still more impressively controls a
wide canvas featuring interstellar warfare, the environmental
degradation of an Edenic planet, and human Transcendence; the central
section of the novel, where the hero finds himself reincarnated as an
"Egon" or soul-like entity (see Identity), displeased some critics,
though it is in fact an effective handling of a traditional sf
displacement of ideas from Metaphysics or Religion.
Rapidly shifting fashions in the SF community of writers, critics, and readers means standards of what does and does not constitute hard SF means that Shaw's 1969 novel might be considered Hard SF today. This answer posits a difference between hard SF and Hard SF, where hard SF keeps a scientific attitude irrespective of its subject matter, while Hard SF stays close to science as it is known. The two explanations of hard SF and Hard SF below serve as illustrations.
Hard sf should not, however, wilfully ignore or break known scientific
principles, yet stories classified as "hard sf" often contain, for
example, ESP, Superman, Faster-than-Light and Time-Travel themes (see
also Imaginary Science). Occasionally it is characterized by auctorial
lecturing about the story's supposed scientific underpinning, a
didacticism which may lapse into numbing Infodumps. While a rigorous
definition of "hard sf" may be impossible, perhaps the most important
thing about it is, not that it should include real science in any
great detail, but that it should respect the scientific spirit; it
should seek to provide natural rather than supernatural or
transcendental explanations for the events and phenomena it describes.
Hard SF can be described as "Hard sf is the form of imaginative
literature that uses either established or carefully extrapolated
science as its backbone."
Source: Encyclopedia of SF entry of hard SF
This answer will provide a worked example of how dualism can be introduced into hard SF. (This answer has deliberately assumed the broader form, because Hard SF proper can be thought as a more rigorous form of its broader sibling. By first establishing it is then possible to determine the steps, if possible, needed to achieve the quality of Hard SF.)
Firstly, to remind ourselves of what constitutes dualism. For preference, the Cartesian model of dualism will be used.
Dualism is closely associated with the thought of René Descartes
(1641), which holds that the mind is a nonphysical—and therefore,
non-spatial—substance. Descartes clearly identified the mind with
consciousness and self-awareness and distinguished this from the brain
as the seat of intelligence.6 Hence, he was the first to formulate
the mind–body problem in the form in which it exists today.
Since hard SF pays attention to science rather invent a home-brewed variety of dualism to introduce into hard SF is better to make use of an existing quasi-scientific version of dualism. So instead inventing a version of dualism from whole cloth, there is a ready made quasi-scientific architecture that postulates dualism in a scientific context.
This model of dualism has been proposed by the Nobel Laureate Sir John Eccles, an eminent neurophysiologist.
Sir John Carew Eccles AC FRS FRACP FRSNZ FAA4 (27 January 1903 – 2
May 1997) was an Australian neurophysiologist and philosopher who won
the 1963 Nobel Prize in Physiology or Medicine for his work on the
synapse. He shared the prize with Andrew Huxley and Alan Lloyd
Hodgkin.
The Australian Academy of Science has an excellent article on the life and times of Sir John Eccles. While dealing his scientific career, research achievements, and his character as a person, it also has a good summary of his philosophical position on the mind-brain problem. Eccles was a Fellow of the Academy.
Eccles originally published first about dualist ideas as Hypotheses relating to the brain-mind problem. Nature 168, 53-57. This was followed by numerous articles, papers and books. This may seem a trite remark but the quasi-scientific doesn't come much classier than when proposed by a Nobel Prize winner who gets it published first in Nature. Frankly, it doesn't get much more prestigious than that.
Eccles searched for answers to a set of essential questions:
- how can Man's enormous capacity for thinking, memory, and emotional feeling and expression be explained?
- how can the 'Will' have such a strong and precise effect on our skeletal muscles during voluntary movement? since our intentions
('Will') appear so strong, can they lead to a change of brain
substrates, both structurally and functionally?
- can a mind-brain interaction be localized to certain, selected parts of the brain, or even to specific cells or synapses?
- which physiological, chemical and physical processes are associated with the mind-brain interaction?
His intention was to develop testable propositions in relation to
these questions. In The Self and Its Brain (1994, p.355) he
summarized his views on the mind-brain interaction: 'It is a very
strong dualism and raises the most severe scientific problems in
relationship to the interface between the world of matter-energy, in
the special instance of the liaison area of the brain, and the world
of states of consciousness that is referred to as the self-conscious
mind. Briefly, the hypothesis states that the self-conscious mind is
an independent entity that actively engages in the reading out from a
multitude of active centres in the modules of the liaison areas of the
dominant cerebral hemisphere.'
Eccles maintained that conscious experience is provided by the
self-conscious mind by itself, and not by the neural machinery of the
brain with its excitatory and inhibitory synaptic interactions (450,
p.362). He further proposed that the mind-brain liaison has traffic in
both directions, from the brain to the mind in perception and from
mind to brain in willed action (111, p.281). His term liaison brain
included all those areas of the cerebral cortex that are potentially
capable of being in direct liaison with the self-conscious mind, and
he located this liaison brain in the cerebral cortex of the dominant
hemisphere, but only in those areas which have linguistic and
ideational performance. Further, he felt that a small part, maybe less
than a tenth of the cortex, in the right state of activity would be
enough to give an effective mind-brain liaison (111, p.283). To
illustrate the mind-brain interaction in the liaison areas, Eccles
used an analogy: 'a multiple scanning and probing device that reads
out from and selects from the immense and diverse patterns of activity
in the cerebral cortex and integrates these selected components, so
organizing them into the unity of conscious experience' (1994, p.363).
The language Eccles used here is similar to that used by a
neuroscientist to explain neuronal interaction in an activated
cortical area. He stated, however, that the self-conscious mind is not
identical to some physical part of the cerebral cortex like cells or
synapses.
Later formulations of his concept of the mind-brain problem and its role in consciousness embraced ideas from, naturally enough, quantum mechanics. This can be seen clearly in the following work published in 1994.
How the Self Controls Its Brain1 is a book by Sir John Eccles, proposing a theory of philosophical dualism, and offering a
justification of how there can be mind-brain action without violating
the principle of the conservation of energy. The model was developed
jointly with the nuclear physicist Friedrich Beck in the period
1991-1992.
Eccles called the fundamental neural units of the cerebral cortex
"dendrons", which are cylindrical bundles of neurons arranged
vertically in the six outer layers or laminae of the cortex, each
cylinder being about 60 micrometres in diameter. Eccles proposed that
each of the 40 million dendrons is linked with a mental unit, or
"psychon", representing a unitary conscious experience. In willed
actions and thought, psychons act on dendrons and, for a moment,
increase the probability of the firing of selected neurons through
quantum tunneling effect in synaptic exocytosis, while in perception
the reverse process takes place.
Source: John C. Eccles, How the Self Controls its Brain, Berlin: Springer-Verlag, 1994. ISBN 3-540-56290-7. Quoted here
The following papers are examples of his collaboration with Friedrich Beck when brain activity, consciousness and quantum mechanics are considered.
F Beck and JC Eccles, Quantum aspects of brain activity and the role of consciousness, Proc. Natl. Acad. Sci. U.S.A. 89 (23): 11357–11361.
Friedrich Beck, John C. Eccles (1998). "Quantum processes in the brain: A scientific basis of consciousness". Cognitive Studies: Bulletin of the Japanese Cognitive Science Society. 5 (2): 95–109.
Summarizing Eccles' model: it assumes extraphyical entities he called “psychons” influence bundles of “dendrons” inducing activity in the brain. This activity in turn is responsible for consciousness, memory, cognition, and self-awareness. Basically it represents what is loosely called mind. This model does not consider these mental or psychological properties can arise from the information processing capacities of the material brain.
Thus far, this answer has dealt with the Eccles brain activity-mind-consciousness model. It is time to speculate on what consequences would be if this model corresponded to a putative reality.
Firstly, quantum mechanics would need to be altered. Calculations show that the kind of macroscopic effects on brain proposed in the Eccles-Beck schema do not exist. So turning this on its head, if Eccles-Beck was right then such macroscopic quantum effects must exist.
Eccles embrace of quantum mechanics came much later in his long-term flirtation with dualism. This means that quantum mechanics isn't essential to Ecclesian dualism. For the moment it can be disregarded unless later on we discover there are good reasons for bringing back into the picture.
One of the questions raised by the OP is the following: ---
“The resulting universe should be enough like ours that the setting of
early 20th century civilization would be the same. Clearly, the kinds
of evidence that ruled out dualism in the real universe would be
exactly the opposite, and these results, appearing in the 20th century
with brain scans and probes and such, would be the point where this
fictional universe diverges from ours. ”
Frankly, no. With Ecclesian dualism the real universe will be exactly the same. The brain scanning and probes of the twentieth century wouldn't have been capable of detecting the influence of psychons on the brain's activity. They lacked both the precision and resolution necessary to observe the phenomena in question. It is only now in the early twenty-first century that brain scanning technology is beginning to approach the sensitivity and the information processing capacity to determine the existence of the coordinated brain activity induced by psychons.
In another answer to this question this author was ready to suggest that extraphysical entities might engender consciousness in computers. After all, computers are simply form of organized physical substrate upon which the extraphysical entities might act. However, in terms of Eccles dualism this seems unlikely for the following reasons.
Firstly, computers are crude and highly coarse grained pieces of physical substrate. Wholly lacking in the complexity, fine-grained structure, and low-energy requirements for interaction of the organic brain. Secondly, living brains have been in existence for many millions, if not billions of years. This is more than enough time for the psychons to evolve and adapt themselves to the brains of biological organisms. Computers on planet Earth have been around for less than a century. Even if there are computers in the rest of the universe they may not have been in existence long enough for psychon evolution to adapt themselves to computers. This suggests that the spontaneous appearance of conscious computers is unlikely. Although should it happen this could be evidence for the existence of Ecclesian psychons.
This is unlike the OP's suggestion that the differences won't appear until around the Second World War. But ours could be a world on the threshold of discovery that ours is a universe where dualism is part of its reality.
In hard SF terms, this means, within this context, that a foundation has been laid for a putative universe that is dualistic in nature, although that dualism exists at a subtle and not easily detected level. Of course, once technology is developed that reveals the existence pf psychons and indicates their role in generating consciousness in our brains there will follow further developments to observe them better and possibly commence communication with psychonic realm.
There is one further suggestion and hinges on this question: why would extraphysical entities like psychons want to interact with our brains to modulate them in such a way as to generate consciousness? One possible answer is that the domain in which the extraphysical entities exist is so vast that they cannot communicate with each other and it is only by orchestrating our brain activity and thereby generating most of our behaviour that they contact each other. This does indicate that the whole human activity may be without any meaning or value except as a communications medium for extraphyical entities.
This could also include the conscious behaviour of every biological organism on the planet with sufficiently developed and complex neurological systems. Current thinking has moved beyond Descartes' belief that animals were merely machines without any consciousness. Evolution does indicate that some form of consciousness exists throughout the Animal Kingdom. There are even possibilities that plants might communicate too. If they can do that, then the further that they possess consciousness cannot entirely be ruled out.
In conclusion, this answer has adopted the Eccles model of brain activity to explain how consciousness might arise through the mediation of non-physical entities he called “psychons” that influences dendritic bundles in the cortex. It has made suggestions how this might be adapted and adopted into hard SF. This has been an exercise in world building. To erect a piece of quasi-scientific architecture, to consider some of its aspects and its possible deviations from the quotidian world. However, the rest that follows from this conceptual framework and how it might be used is the business of the fiction writer. While the work of world building isn't truly over, once the fiction is constructed, then new problems and new issues about this world will arise and need to be solved. But the primary world building is over in introducing a specific form of dualism into the fictional context of hard SF.
