Remember from the last part of this line of thinking, how we get a story either from the top or the bottom when things change? And to keep the life in our bodies doing what it does, we use the stories from the top so we don't have to spend more life to change with everything else that's changing? Things we eat, smoke, drink, or snort that make us very surprised for a few hours ("psychedelics") work by letting us relax our use of stories from the top. One of these stories is "I"- that "I" stands out and away from everything else.

Most of the time, our brains rule our stories with one or a few stories that come first, and those few stories carry all the other stories. This ruling closes the lower stories so that they fit with the higher stories. So when the rule is relaxed, more new facts that come from the bottom are allowed to change the whole. This is sort of like when you heat a metal enough that it is easier to move around, except with our brains. So psychedelics make it easier to move between stories, between ways of being. Many of the ways that people live (that they say they don't really want to live like) come from having very strong higher stories (or priors) that make all the other stories short. This may happen because there was a surprise that was very painful, and so they formed very strong stories to hide in to avoid getting surprised in the same way again. There are two ways to deal with the feeling of surprise: accepting change or ignoring it, and forming very strong stories may help to ignore changes that would be very surprising to accept. In this case, strong stories help ignore things that may surprise.

Without psychedelics, people who move their attention (as in meditation) have been known to have let go of "I" and the strong, higher stories that we hold onto. For those studied, it does not seem like what happens to them is as strong as what may happen with psychedelics, but they both have people relaxing their stories which close in all their other stories, which relaxes the rule of those few strong stories. So let's see what this gives us a clue about, by looking at what some spiritual traditions say.

From Buddhism, we have the Four Noble Truths:

1. The Noble Truth of suffering. Birth is suffering. Old age is suffering. Sickness is suffering. Death is suffering. Sorrow, grief, mental anguish, and disturbance are suffering. To be with those you dislike is suffering. To be separated from those you love is suffering. Not having what you long for is suffering. In other words, to grasp the Five Aggregates as though they constitute a self is suffering.
2. The Noble Truth of the cause of suffering. It is the desire to be born again, delight in being born again, attached to the pleasures found in this and that. There is the craving for sense pleasures, for becoming, and for not becoming any more.
3. The Noble Truth of ending suffering. It is the fading away and ending of craving without any trace. It is giving up, letting go of, being free from, and doing away with craving.
4. The Noble Truth of the Path that leads to the end of suffering. It is the Noble Eightfold Path of Right View, Right Thinking, Right Speech, Right Action, Right Livelihood, Right Diligence, Right Mindfulness, and Right Concentration.

And Wikipedia shows this interpretation:

1. Dukkha – "incapable of satisfying",[web 4] "the unsatisfactory nature and the general insecurity of all conditioned phenomena"; "painful". Dukkha is most commonly translated as "suffering". According to Khantipalo, this is an incorrect translation, since it refers to the ultimately unsatisfactory nature of temporary states and things, including pleasant but temporary experiences. According to Emmanuel, Dukkha is the opposite of sukha, "pleasure", and it is better translated as "pain".
2. Samudaya – "origin", "source", "arising", "coming to existence"; "aggregate of the constituent elements or factors of any being or existence", "cluster", "coming together", "combination", "producing cause", "combination", "rising".
3. Nirodha – cessation; release; to confine; "prevention, suppression, enclosing, restraint"
4. Marga – "path"

Looking at the page on Dukka, we find:

Duḥkha is commonly translated as "suffering", "unhappiness", "pain", "unsatisfactoriness" or "stress".

And maybe the word 'Duhka' comes from talking about the feeling of having a bumpy chariot ride, like your car having a flat tire. Let's also call it 'friction'.

Now we'll revisit the Four Noble Truths in simpler terms:

First, Life is heavy. Dying is heavy. Getting sick is heavy. Being joined with what you don't like is heavy. Being away from what you like is heavy. Not getting what you want is heavy. Holding on to "I" is heavy. Holding on to the way your body is, the way things are, and the way you see things is heavy.
Second, wanting things to be a few ways is what makes things heavy.
Third, closing your wants allows you to let go of what is heavy.
Fourth: So this is the way to let go of what is heavy.

In terms of Peters, McEwen, Friston, Carhart-Harris, & company, we might say the Four Noble Truths go like this:

First, you are uncertain, so you are surprised. This surprise causes stress. Surprise at surprise and stress leads to more stress, which leads to pain and disease. In turn, this leads you to further weight certain priors that rule all information, which lead to even more stress later.
Second, you have expectations, or priors (what we called 'stories' earlier) about how the world will go. When those expectations are not met, you are more surprised. Having stronger priors leads to bigger surprises that result in more stress.
Third, if you relax your priors, you will be less stressed.
Fourth: So this is how you deal with uncertainty.

What about something like the Heart Sutra?

Form is nothing more than emptiness, emptiness is nothing more than Form. Form is exactly emptiness, and emptiness is exactly Form. The other four aggregates of human existence -- feeling, thought, will, and consciousness -- are also nothing more than emptiness.
All things are empty.

So we might say:
What things look like, feel like, sound like, and everything that stands out, aren't how they are. That is made up. What is made up is how things look, feel, sound, and everything that stands out.

From the point of view of uncertainty, stress, and the anarchic brain, then: How the world appears to be, the nature of reality (perhaps we'll tie-in Hoffman's Interface Theory of Perception at some point), and even our vision and our sense of our bodies (consider: proprioception) are all informed by priors. Those priors, those expectations, are never certain. Since the feeling of existence and reality itself is based in those priors, everything is fundamentally uncertain.

What about something like the Bardo, from The Tibetan Book of the Dead? Let's look at a part of that.

Are you oblivious to the sufferings of birth, old age, sickness, and death?
There is no guarantee you will survive, even past this very day!
The time has come to develop perseverance in practice.
For, at this singular opportunity, you could attain the everlasting bliss.
So now is not the time to sit idly.
But starting with death, you should bring your practice to completion.
The moments of our life are not expendable.
And the circumstances of death are beyond imagination.
All phenomena are selfless, empty, and free from conceptual elaboration.
In their dynamic they resemble an illusion, mirage, dream, or reflected image. All phenomena are naturally uncreated.
They neither abide nor cease, neither come nor go.
They are without objective referent, signless, ineffable, and free from thought.

From this we might get:
Death is always something that can happen, and no one knows when or how they will die. So pay attention, and notice that what Is cannot be spent, because there is nothing to spend. What is shown does not have anything behind what is shown. It is what is, and nothing more. Together, what is shown is a sort of mirror, a dream, something to look at that is not more than the act of seeing. So everything that is shown is made to fall away. They do not live outside us, they leave no track, and nothing can be said of them.

Or: all priors are uncertain. The expectation that forms them is made up, and changes as soon as new information comes in. One thing that seems certain is that everything changes- surprise is guaranteed. A lot of our surprise has to do with death- we are surprised about death, and this causes stress. So get used to death.

Memento Mori? Perhaps that's good place to stop with Buddhism. Next time, we'll consider Stoicism in light of all this.