When I first encountered Andy Norman’s argument for a mental immune system,1 I absolutely loved it. Andy and I had been friendly acquaintances for years, sharing broadly similar worldviews, and I had clearly developed a predisposition to like his work. Both consciously and subconsciously, I wanted to use my research in evolutionary philosophy to support his new idea, and my mind swarmed with reinforcements to bolster his arguments. Five different elements immediately came to mind.
- One of the main tools for understanding any evolutionary problem is Tinbergen’s Four Questions.2 This combination of proximate, ultimate, static, and historical views yields a comprehensive understanding of all things biological. With mental immunity, answers to three of the four Tinbergen questions seemed immediately clear and compelling. Andy’s book laid out the function of mental immunity—protecting thinkers from harmful thoughts through the doubts that seem to naturally arise within us. Facts about child development and ongoing education could easily show the ontogeny of how mental immunity develops over the course of a lifetime of learning. And the phylogeny of how mental immunity might have developed over evolutionary history needs some details to be filled in but the general arc from nothing to a well-developed mental immune system seems entirely plausible. The big hole left was just mechanisms. The field of mental immunity still needs its Metchnikoff discovering white blood cells swarming to the scene of an injury.3 But if answers to three of Tinbergen’s four questions were leading in the same direction, this seemed like just a matter of time.
- In the world of the mind, however, a simple microscope won’t do for observing mechanisms. I have been diving into the field of consciousness studies for the last few years, trying to develop an evolutionary theory4 for the slow emergence and development of that enigmatic feeling of “what it’s like” to be something. But that field is a mess. It is still trying to sort through dozens of different candidates for explanations.5 In short, we don’t yet know how minds are produced, so how could we know how mental immunity is produced? And yet, some candidates seem more promising and helpful to Andy’s idea than others. Through them, we may be able to start to glimpse the coming together of a grand evolutionary explanation of consciousness, which has a place in it for the existence and development of mental immunity. For example:
- Anil Seth’s description of the brain as a prediction machine6 provides a basic model for understanding how minds build models of the world and try to avoid surprises (which can obviously have bad evolutionary consequences). Mental immunity seems protective of these predictive models by raising doubts about observations that contradict our beliefs.
- Karl Friston’s free energy principle7 attempts to provide a physical description of how self-organizing systems will generally minimize the differences between internal models and the information that comes to them through their sensory apparatus. In conscious entities like ourselves, this difference is registered as surprise. This theory is highly complex and still being debated, but its details could inform some of the mechanisms for mental immunity.
- Mark Solms’ theory of affect as the wellspring of consciousness8 builds on Friston’s free energy principle to take on the “hard problem”9 of consciousness. Whether or not that problem can be “solved” (I have my doubts), Solms provides a strong argument that affect, or the feeling of positive or negative valence,10 is the bedrock upon which the rest of consciousness is built. This sounds particularly useful for a theory of mental immunity which seeks to explain how and why we judge particular ideas as positive or negative.
Looked at individually, these five things do indeed seem to provide promising support for the idea of mental immunity. The problem, however, is that upon reflection they came to me in a swarm of reinforcements that is the mirror image of the swarm of doubts that Andy uses as evidence for the workings of a mental immune system. If minds can swarm to both reject an idea and support an idea, then is there a difference in these swarms or is there just something more general going on?
In David Sloan Wilson’s book The Neighborhood Project,11 Wilson included a chapter called “the parable of the immune system” which explained how innate biological building blocks (the genes that build our immune systems) can give rise to malleable, open-ended, learning systems (the immune systems themselves), which are capable of responding and adapting to the environments that are encountered throughout one’s lifetime. Wilson uses this parable to argue that we can think similarly about our minds and our cultures—they may be built from concrete genetic materials, but they are similarly adaptive (i.e., not hard-wired).12
But this plasticity in our minds is not infinite! It would be incredibly wasteful to have to rethink everything we have ever learned every time we encounter something new. We may not be hard-wired, but our minds do settle into grooves because our neurons “fire together and wire together”13 during years of building and refining predictive models that continue to be confirmed.
Reflecting on all of this now, I wonder if the nature of our minds is so much more plastic and adaptive than our bodies that it creates a distinction between the two realms that makes “mental immune systems” not quite accurate enough as a label for what is happening there. With bodies, it’s much easier to distinguish between “us” and “them”. With minds, that dichotomy is relative and learned, and it remains fluid over a lifetime. One woman’s mental parasite is another man’s mental nutrition. So also can one child’s mental parasite become a mental nutrition for that person as an adult. Identifying which ones are definitively good or bad would require a solution to the age-old moral question of what is good or bad. Andy takes strides towards that in his book, but the discussion of that is for another symposium.
After digging deeper here, the actions of the so-called mental immune system may now appear to me to just be part of a larger, more generalizable function of the brain. In a fascinating paper by Pamela Lyon14 who studies the evolution of cognition, Lyon included a table that lists all the types of cognitive abilities that have developed over the evolutionary history of life. Among these is the skill of “problem-solving” where minds somehow bubble up ideas, both good and bad, to try and fix something that needs fixing.15 Any time we are faced with new information, it becomes a problem to try to incorporate this into our current predictive model without having to rewire the whole thing. When our minds swarm with doubts, it may be easier to think of this as problem-solving for our predictive worldview, rather than the actions of some kind of neuronal version of white blood cells. That way, the swarming of reinforcements that I personally experienced can also be explained by the same mechanism. This seems more parsimonious.
Besides the swarming of doubts, Andy also notes that inoculation theorists have shown that exposure to weakened information threats will tend to “inoculate” a mind against more formidable versions of those same threats. But perhaps this isn’t inoculating a mind against bad ideas so much as scaffolding a worldview in another rigid direction. Once a predictive model is built in one direction, it becomes harder to change it absent some catastrophic deconstruction.16 If I’m right, then mind inoculation will only work if it is received from a trusted source. Even if the weakened idea is a “bad” one, whenever we perceive the inoculation as coming from “them” then the inoculation should not work as intended. Such attempts may even backfire. In fact, don’t we see this all the time with the sharing, belief, and disbelief of ideas among friends, foes, and relatives?
After initially accepting the metaphor of mental immunity as a useful gift from a cherished friend, my more deeply ingrained worldview now appears to be casting doubts upon it. These are such speculative areas of inquiry, though, that I take pains to keep my own predictive model from becoming too set in any one direction. I, therefore, look forward to comments and additional entries in this symposium to help further shape these beliefs.
 See my early thoughts here: “An Evolutionary Theory of Consciousness and Free Will.”
 See, for example, my post “A (sorta) brief history of consciousness and its definitions” which cites dozens of theories from scientists, philosophers, and dictionaries.
 See https://en.wikipedia.org/wiki/Free_energy_principle for a general overview. Solms and Panksepp also discuss Friston’s ideas and its impact on surprise in their paper “The ‘Id’ Knows More than the ‘Ego’ Admits.”
 Solms’ 2022 book Hidden Spring expands upon his 2019 paper “The Hard Problem of Consciousness and the Free Energy Principle.”
 Jeff Hawkins’ book A Thousand Brains posits one way that multitudes of trials and errors bubble up from the individual elements of the brain until a sort of democratic solution appears in consciousness.
 Lee McIntyre’s How to Talk to a Science Denier hints, at least anecdotally, that Flat Earth believers have tended to have some trauma in their past that ruined their ability to place their trust in more conventional people’s predictive models.