Once a week.
Subscribe to our weekly newsletter.
What can Avicenna teach us about the mind-body problem?
The Persian polymath and philosopher of the Islamic Golden Age teaches us about self-awareness.
If the heavens vanished, they wondered, would time continue to pass? If existence were distinct from essence, would that mean that existence itself must exist? Can God turn your household servant into a horse, so that you come back home to find it has urinated all over your books?
But the most famous is the so-called 'flying man' thought experiment, devised by the most influential philosopher of the Islamic world, Avicenna (in Arabic, Ibn Sīnā, who lived from 980 to 1037 CE). Imagine, he says, that a person is created by God in mid-air, in good condition but with his sight veiled and his limbs outstretched so that he is touching nothing, not even his own body. This person has no memories, having only just been created. Will his mind be a blank, devoid as it is of past or present sensory experience? No, says Avicenna. He will be aware of his own existence.
Three questions immediately arise. First, when Douglas Adams, the author of The Hitchhiker's Guide to the Galaxy (1978), imagined a whale popping into existence in mid-air above an alien planet, had he been reading Avicenna? I have no idea, but I like to think so.
Second, is Avicenna right that the 'flying man' would be self-aware? Well, it's important to realise that Avicenna does not attempt to argue that the flying man would know that he exists. Rather, he takes it as obvious. In one version, he even tells readers that we should imagine ourselves being so created. If we put ourselves in the flying man's dangling shoes, we should just see that we would be self-aware. Indeed, this turns out to be a fundamental idea in Avicenna's philosophy. He thinks that we are all always self-aware, even when we're asleep or focusing hard on something other than ourselves. Paradoxically, we're often not aware of being self-aware: it is the non-interruptive background music of human psychology, something we notice only when our attention is called to it, a pre-reflective awareness of self. The flying man thought experiment is itself one way to call attention to this self-awareness: Avicenna calls it a tanbīh, meaning a 'pointer' to something.
Our self-awareness is a foundation for our first-person perspective on things. It's a sign of this that when I see, imagine or think something, I can immediately apprehend that I am seeing, imagining or thinking about that thing. Any other form of cognition – any awareness of other things – presupposes awareness of oneself.
Incidentally, you might object that the flying man would have certain forms of bodily awareness despite his lack of vision, hearing and so on. Wouldn't he at least sense the location of his limbs by another form of sensation, namely proprioception? Imagine you are in total darkness and your arm is not resting on anything: proprioception is the sense that tells you where it is. This is indeed a problem for the thought experiment as Avicenna sets it up, but it isn't really philosophically decisive. One can just modify the scenario by adding that God blocks the man's ability to use proprioception, or that the flying man's proprioceptive faculty happens to be defective. Avicenna's claim will then be that, even under these circumstances, the flying man would be aware of himself.
Now for the third, and hardest, question: what does the flying man thought experiment prove? Avicenna draws a surprising conclusion: it shows that we are not identical with our bodies. Just consider. The flying man is aware of himself; he knows that he exists. But he is not aware of his body; he doesn't know that his body exists, nor indeed that any body exists. And if I am aware of one thing but not another, how can those two things be identical?
This sounds pretty persuasive, until you reflect that one can be conscious of a thing without being conscious of everything about it. You, for example, have been aware of reading this article for the past few minutes, but you haven't been aware of reading something written while Dixieland jazz was playing. It would be a mistake to conclude from this that the article is not something written with Dixieland jazz playing. In fact, that is exactly what it is. To put it another way, the flying man could be aware of his self without realising that his self is a body. Contemporary philosophers would say that Avicenna is mistakenly moving from a 'transparent' to an 'opaque' context, which is basically a fancy way of saying what I just said.
Efforts have been made to spare Avicenna from this mistake. One possible way to rescue the argument would go like this. Avicenna is trying to criticise another way of thinking about the soul, one that goes back to Aristotle. According to the theory he rejects, the soul is so closely associated with the body that it can only be understood as an aspect or organising principle of the body, which Aristotle called the body's 'form'. The thought experiment is designed to show that this is wrong. It does so by calling to our attention that we have a means of access to our souls apart from bodily sensation, namely self-awareness.
How would this refute Aristotle? Well, consider again just why it is that the flying man is not aware of his body. It is because he is not currently using his senses and has never done so (he only just started existing, remember), and sense perception is, Avicenna assumes, the only way to become aware of any body. If this is right, then anything that the flying man grasps without using sense perception is not a body, not material. Since he does grasp his soul without using sense perception, his soul is therefore not a body.
On this reading, Avicenna would be helping himself to a pretty big assumption, which is that bodies can be discovered only by the senses. You can see, hear, touch, taste or smell them, but otherwise you can never so much as know that they exist. Since for Aristotle the soul was a form of the body, if you couldn't experience the body, you would not, on his account, have access to the soul; and yet, Avicenna claims, the falling man would have access to his soul.
I suspect this is (at least in part) what he had in mind in creating this thought experiment. But that's not to say that I'm convinced. All Avicenna has really done is to throw down a challenge to his materialist opponents: show me how a body could be aware of itself without using sensation to do so.
Philosophy in the Islamic World by Peter Adamson is out now through Oxford University Press.
- Do Philosophy Courses Need to Be "Decolonized"? - Big Think ›
- 10 Golden Age Philosophers, and Why You Should Know Them ... ›
Scientists are using bioelectronic medicine to treat inflammatory diseases, an approach that capitalizes on the ancient "hardwiring" of the nervous system.
- Bioelectronic medicine is an emerging field that focuses on manipulating the nervous system to treat diseases.
- Clinical studies show that using electronic devices to stimulate the vagus nerve is effective at treating inflammatory diseases like rheumatoid arthritis.
- Although it's not yet approved by the US Food and Drug Administration, vagus nerve stimulation may also prove effective at treating other diseases like cancer, diabetes and depression.
The nervous system’s ancient reflexes<p>You accidentally place your hand on a hot stove. Almost instantaneously, your hand withdraws.</p><p>What triggered your hand to move? The answer is <em>not</em> that you consciously decided the stove was hot and you should move your hand. Rather, it was a reflex: Skin receptors on your hand sent nerve impulses to the spinal cord, which ultimately sent back motor neurons that caused your hand to move away. This all occurred before your "conscious brain" realized what happened.</p><p>Similarly, the nervous system has reflexes that protect individual cells in the body.</p><p>"The nervous system evolved because we need to respond to stimuli in the environment," said Dr. Tracey. "Neural signals don't come from the brain down first. Instead, when something happens in the environment, our peripheral nervous system senses it and sends a signal to the central nervous system, which comprises the brain and spinal cord. And then the nervous system responds to correct the problem."</p><p>So, what if scientists could "hack" into the nervous system, manipulating the electrical activity in the nervous system to control molecular processes and produce desirable outcomes? That's the chief goal of bioelectronic medicine.</p><p>"There are billions of neurons in the body that interact with almost every cell in the body, and at each of those nerve endings, molecular signals control molecular mechanisms that can be defined and mapped, and potentially put under control," Dr. Tracey said in a <a href="https://www.youtube.com/watch?v=AJH9KsMKi5M" target="_blank">TED Talk</a>.</p><p>"Many of these mechanisms are also involved in important diseases, like cancer, Alzheimer's, diabetes, hypertension and shock. It's very plausible that finding neural signals to control those mechanisms will hold promises for devices replacing some of today's medication for those diseases."</p><p>How can scientists hack the nervous system? For years, researchers in the field of bioelectronic medicine have zeroed in on the longest cranial nerve in the body: the vagus nerve.</p>
The vagus nerve<img type="lazy-image" data-runner-src="https://assets.rebelmouse.io/eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJpbWFnZSI6Imh0dHBzOi8vYXNzZXRzLnJibC5tcy8yNTYyOTM5OC9vcmlnaW4uanBnIiwiZXhwaXJlc19hdCI6MTY0NTIwNzk0NX0.UCy-3UNpomb3DQZMhyOw_SQG4ThwACXW_rMnc9mLAe8/img.jpg?width=1245&coordinates=0%2C0%2C0%2C0&height=700" id="09add" class="rm-shortcode" data-rm-shortcode-id="f38dbfbbfe470ad85a3b023dd5083557" data-rm-shortcode-name="rebelmouse-image" data-width="1245" data-height="700" />
Electrical signals, seen here in a synapse, travel along the vagus nerve to trigger an inflammatory response.
Credit: Adobe Stock via solvod<p>The vagus nerve ("vagus" meaning "wandering" in Latin) comprises two nerve branches that stretch from the brainstem down to the chest and abdomen, where nerve fibers connect to organs. Electrical signals constantly travel up and down the vagus nerve, facilitating communication between the brain and other parts of the body.</p><p>One aspect of this back-and-forth communication is inflammation. When the immune system detects injury or attack, it automatically triggers an inflammatory response, which helps heal injuries and fend off invaders. But when not deployed properly, inflammation can become excessive, exacerbating the original problem and potentially contributing to diseases.</p><p>In 2002, Dr. Tracey and his colleagues discovered that the nervous system plays a key role in monitoring and modifying inflammation. This occurs through a process called the <a href="https://www.nature.com/articles/nature01321" target="_blank" rel="noopener noreferrer">inflammatory reflex</a>. In simple terms, it works like this: When the nervous system detects inflammatory stimuli, it reflexively (and subconsciously) deploys electrical signals through the vagus nerve that trigger anti-inflammatory molecular processes.</p><p>In rodent experiments, Dr. Tracey and his colleagues observed that electrical signals traveling through the vagus nerve control TNF, a protein that, in excess, causes inflammation. These electrical signals travel through the vagus nerve to the spleen. There, electrical signals are converted to chemical signals, triggering a molecular process that ultimately makes TNF, which exacerbates conditions like rheumatoid arthritis.</p><p>The incredible chain reaction of the inflammatory reflex was observed by Dr. Tracey and his colleagues in greater detail through rodent experiments. When inflammatory stimuli are detected, the nervous system sends electrical signals that travel through the vagus nerve to the spleen. There, the electrical signals are converted to chemical signals, which trigger the spleen to create a white blood cell called a T cell, which then creates a neurotransmitter called acetylcholine. The acetylcholine interacts with macrophages, which are a specific type of white blood cell that creates TNF, a protein that, in excess, causes inflammation. At that point, the acetylcholine triggers the macrophages to stop overproducing TNF – or inflammation.</p><p>Experiments showed that when a specific part of the body is inflamed, specific fibers within the vagus nerve start firing. Dr. Tracey and his colleagues were able to map these relationships. More importantly, they were able to stimulate specific parts of the vagus nerve to "shut off" inflammation.</p><p>What's more, clinical trials show that vagus nerve stimulation not only "shuts off" inflammation, but also triggers the production of cells that promote healing.</p><p>"In animal experiments, we understand how this works," Dr. Tracey said. "And now we have clinical trials showing that the human response is what's predicted by the lab experiments. Many scientific thresholds have been crossed in the clinic and the lab. We're literally at the point of regulatory steps and stages, and then marketing and distribution before this idea takes off."<br></p>
The future of bioelectronic medicine<img type="lazy-image" data-runner-src="https://assets.rebelmouse.io/eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJpbWFnZSI6Imh0dHBzOi8vYXNzZXRzLnJibC5tcy8yNTYxMDYxMy9vcmlnaW4uanBnIiwiZXhwaXJlc19hdCI6MTYzNjQwOTExNH0.uBY1TnEs_kv9Dal7zmA_i9L7T0wnIuf9gGtdRXcNNxo/img.jpg?width=980" id="8b5b2" class="rm-shortcode" data-rm-shortcode-id="c005e615e5f23c2817483862354d2cc4" data-rm-shortcode-name="rebelmouse-image" data-width="2000" data-height="1125" />
Vagus nerve stimulation can already treat Crohn's disease and other inflammatory diseases. In the future, it may also be used to treat cancer, diabetes, and depression.
Credit: Adobe Stock via Maridav<p>Vagus nerve stimulation is currently awaiting approval by the US Food and Drug Administration, but so far, it's proven safe and effective in clinical trials on humans. Dr. Tracey said vagus nerve stimulation could become a common treatment for a wide range of diseases, including cancer, Alzheimer's, diabetes, hypertension, shock, depression and diabetes.</p><p>"To the extent that inflammation is the problem in the disease, then stopping inflammation or suppressing the inflammation with vagus nerve stimulation or bioelectronic approaches will be beneficial and therapeutic," he said.</p><p>Receiving vagus nerve stimulation would require having an electronic device, about the size of lima bean, surgically implanted in your neck during a 30-minute procedure. A couple of weeks later, you'd visit, say, your rheumatologist, who would activate the device and determine the right dosage. The stimulation would take a few minutes each day, and it'd likely be unnoticeable.</p><p>But the most revolutionary aspect of bioelectronic medicine, according to Dr. Tracey, is that approaches like vagus nerve stimulation wouldn't come with harmful and potentially deadly side effects, as many pharmaceutical drugs currently do.</p><p>"A device on a nerve is not going to have systemic side effects on the body like taking a steroid does," Dr. Tracey said. "It's a powerful concept that, frankly, scientists are quite accepting of—it's actually quite amazing. But the idea of adopting this into practice is going to take another 10 or 20 years, because it's hard for physicians, who've spent their lives writing prescriptions for pills or injections, that a computer chip can replace the drug."</p><p>But patients could also play a role in advancing bioelectronic medicine.</p><p>"There's a huge demand in this patient cohort for something better than they're taking now," Dr. Tracey said. "Patients don't want to take a drug with a black-box warning, costs $100,000 a year and works half the time."</p><p>Michael Dowling, president and CEO of Northwell Health, elaborated:</p><p>"Why would patients pursue a drug regimen when they could opt for a few electronic pulses? Is it possible that treatments like this, pulses through electronic devices, could replace some drugs in the coming years as preferred treatments? Tracey believes it is, and that is perhaps why the pharmaceutical industry closely follows his work."</p><p>Over the long term, bioelectronic approaches are unlikely to completely replace pharmaceutical drugs, but they could replace many, or at least be used as supplemental treatments.</p><p>Dr. Tracey is optimistic about the future of the field.</p><p>"It's going to spawn a huge new industry that will rival the pharmaceutical industry in the next 50 years," he said. "This is no longer just a startup industry. [...] It's going to be very interesting to see the explosive growth that's going to occur."</p>
Researchers figure out the average temperatures of the last ice age on Earth.
- A new study analyzes fossil data to find the average temperatures during the last Ice Age.
- This period of time, about 20,000 years ago, had the average temperature of about 46 degrees Fahrenheit (7.8 C).
- The study has implications for understanding climate change.
Surface air temperatures during the last ice age.
Credit: Jessica Tierney, University of Arizona
"The Expanse" is the best vision I've ever seen of a space-faring future that may be just a few generations away.
- Want three reasons why that headline is justified? Characters and acting, universe building, and science.
- For those who don't know, "The Expanse" is a series that's run on SyFy and Amazon Prime set about 200 years in the future in a mostly settled solar system with three waring factions: Earth, Mars, and Belters.
- No other show I know of manages to use real science so adeptly in the service of its story and its grand universe building.
Credit: "The Expanse" / Syfy<p>Now, I get it if you don't agree with me. I love "Star Trek" and I thought "Battlestar Galactica" (the new one) was amazing and I do adore "The Mandalorian". They are all fun and important and worth watching and thinking about. And maybe you love them more than anything else. But when you sum up the acting, the universe building, and the use of real science where it matters, I think nothing can beat "The Expanse". And with a <a href="https://www.rottentomatoes.com/tv/the_expanse" target="_blank">Rotten Tomato</a> average rating of 93%, I'm clearly not the only one who feels this way.</p><p>Best.</p><p>Show.</p><p>Ever. </p>
Contrary to what some might think, the brain is a very plastic organ.
As with many other physicians, recommending physical activity to patients was just a doctor chore for me – until a few years ago. That was because I myself was not very active.