Science Sunday 7 August 2022

Science Sunday 7 August 2022

I had a science Sunday; the day revolved around experiencing and learning about science. My friend Claudia inspired us to have a wonderful day. A week ago, she suggested that we might visit The Infinite, a virtual reality (VR) experience centered on life in space. Users experience the project via Oculus VR goggles. I talked with my wife, Mary Ellen, and we thought it would make for a good outing. We met with our friends Claudia and Pat on a sunny morning and journeyed to Tacoma.

On the drive down to Tacoma, we started with a science appetizer. We listened to part of Claudia’s audiobook: “An Immense World: How Animal Senses Reveal the Hidden Realms Around Us” by Ed Yong. The section we listened to was about dogs’ sense of smell, the primary sense for dogs. Since I spend a fair amount of time with my granddog Juniper, it was eye-opening to learn how she views the world. I hadn’t realized that dogs have a separate pathway for air to smell and air to breathe. Different paths let a dog sniff and observe scent many times a second. It was a sound learning snippet on our drive.

When we arrived, we decided we all needed a snack. Pat knew his donuts and remembered a great donut shop, The Original Donut House. After consulting with Google and Siri, we decided the Donut House was defunct. Luckily, Le Duc Donuts was nearby. I fortified myself with a cake donut with coconut sprinkles and green tea.

We went on to The Infinite, a traveling exhibit hosted in the Tacoma Armory. It was interesting to have a cutting-edge technology exhibit hosted in a building constructed in 1908. We went through a brief introduction and then entered an area where we learned how to get the most out of our Oculus VR sets. I found that I needed to have my glasses on to see effectively. The VR set allowed my glasses to fit in, it was slightly uncomfortable, but I adapted quickly.

We got a minute to adjust to the VR set. In our view, our group of four appeared as gold avatars, other visitors as blue avatars, and exhibit staff as green avatars. White dots delineated the floor below us. I found I walked cautiously. We entered the exhibit, and I was awestruck; I was floating in orbit around the Earth with the heavens above. Wow.

In a minute, the outline of the International Space Station (ISS) appeared. I slowly walked towards it and entered.

The station pictured from the SpaceX Crew Dragon, 2021 Source: NASA

Floating around us were orbs; I touched my first orb. The astronaut explained what she was doing in a science experiment on the ISS. I went on to another orb and another. A favorite was the astronaut and cosmonauts preparing and eating appetizers; I was next to the table with them. In another experience, an astronaut was floating toward me. I could look up into another node of the station. I was well above the floor when I looked down. I floated gravity free on orbit around Earth.

Four chapters of seven minutes divide the Infinite experience: Adaptation, Progress, Unity, and Expansion. In between each chapter is a transition of a few minutes. You leave the confines of the station and float above the Earth. There’s some ethereal music coming in via your headphones. The ISS appears in front of you, and you enter the next chapter. I saw the Earth from the cupola, a domed viewing port added to let astronauts see the Earth through large viewing windows. I also floated outside the station; nearby, a SpaceX Crew Dragon capsule was docked, and the solar panels towered above me; what a view.

Most memorable were the crew interactions, the human element, and emotion. There was joy when a crew floated in; sadness when a crew departed. The station crews are “space people,” a term I learned from MIT researcher Ariel Ekblaw. [1]

Near the end, I had something upsetting happen. A message flashed that said a staff member wanted to talk with me. We connected after I lifted my headset. My VR set battery was 16%; I needed to change headsets. I struggled awkwardly to get the headset off; the headset captured my glasses. With my headset off, I was catapulted back to reality. There were a bunch of people standing in a warehouse. It was disconcerting. I asked to leave; I felt I would not reengage with the VR experience. The staff member guided me to an exit. I did talk with a manager and explained my concern; getting a partially charged headset that did not compute to me.

I think we just visited a section of the Metaverse; the experience was terrific despite the glitch. The exhibit is complex; taking it all in on a 35-minute visit is impossible. The good news is that I will get to come back and do the show again. In preparation for my next time, I bought a book about the exhibit: The Infinite, by Phoebe Greenberg and nine co-authors.

After our time in virtual reality, we needed lunch. We picked the Red Elm cafe in the Hilltop neighborhood of Tacoma. It was some great food; I had a vegan breakfast waffle with hashbrowns and a soy latte. Mary Ellen enjoyed a chicken avocado sandwich with a cold latte. The food was delicious, and the staff was friendly and attentive. We met Henry; he teaches crochet lessons. Some of his knitted art was on the wall of the cafe.

On our way home, Claudia gave us another recommendation – to see the documentary AlphaGo. I knew the general story about a Google DeepMind team building an artificial intelligence (AI) program that defeated the world’s best Go player. We started the documentary; I thought we might spend 15 minutes viewing this 90-minute film. Wrong. The film captivated us. I was intrigued by the development of neural networks; I had colleagues who worked in this field in the early 1990s. The struggles of Fan Hui and Lee Sedol against the AlphaGo program was mesmerizing. Sedol learned new insights from AlphaGo; perhaps humans and AIs will team up to reach new levels of learning in the game of Go.

Well, that’s a summary of science Sunday. I woke up Monday morning with the thought of capturing a wonderful day with Mary Ellen, Claudia, and Pat. I found it took me longer than I thought to capture my thoughts in writing; about 2.5 hours from start to finish.

My writing was aided and abetted by visits from Gus the cat, who decided I needed to take an occasional break.

[1] Ariel Ekblaw: Space Colonization and Self-Assembling Space Megastructures | Lex Fridman Podcast #271 One of my favorite podcasts; I always learn something when Lex interviews people.

Going Postal on Inflation

Going Postal on Inflation

I like collecting stamps. My grandmother got me started in 1969 with a six-cent stamp [1] honoring explorer John Wesley Powell, who went down the Colorado River through the Grand Canyon. Here’s a picture:

A few months ago, talked with a friend who is sorting his father’s old stamps. My friend observed that it costs a lot more to mail a letter these days. I agreed and filed that fact away. A few weeks ago, I read that the first-class letter rate increased from 58 to 60 cents. Wow, mailing a letter has risen by ten times since I started collecting in 1969!

I decided to quantify this rise using Postal Service data. I looked at what it cost to mail a one-ounce letter via first class mail from 1885 to 2022. I plotted the first-class postage rate versus time using a logarithmic scale; that makes it easier to view change over time. Note: You can scroll into this plot to see the dates and rates. The formatting and weird spacing after the plot – that’s due to my poor knowledge of WordPress.

I first noticed how flat the left side of the plot was. It cost two cents to mail a letter from 1885 to 1932 except for one interval around World War One; the rate was increased to three cents from 1917 to 1919. So, the rate stayed flat for most of 47 years.

The first long-term increase was from two to three cents in July 1932 during the Depression. This rise of 50%was a decision by the Hoover administration. Now, we might think it was just a penny but keep in mind that the value of a penny in 1932 was equal to about 21 cents in 2022. [2]

First-class postage jumped to 4 cents in August 1958; this was 26 years after the last increase. Another way to think about this is the doubling time, which was 73 years to double from 2 to 4 cents.

Our next doubling of rates from 4 cents to 8 cents happened in 1971, just 13 years. The plot is starting on an upward trend. The increase from six cents in 1969 to 8 cents in 1971 coincides with a significant change for the Post Office, which moved from a government department to an independent United States Postal Service as defined in the Postal Reorganization Act of 1970. President Nixon said: ““Our present postal system is obsolete; it has broken down; it is not what it ought to be for a nation of 200 million people.… And now is the time to act.“ My take is that you might want to hold on to your wallet when a President decides to tinker with the postal system. [3]

Our fastest doubling of postal rates took only seven years during the stagflation years of the 1970s, under the Nixon, Ford, and Carter administrations. [4] These were tough times for the United States; we experienced high inflation with high unemployment. Sadly, the 2020s look like they will mirror the 1970s.

We had another 13-year doubling period in 1991. The inflation-fighting of Fed Chairman Paul Volcker had tamed inflation. We reaped the benefits of lower inflation for the next 30 years; it took that long for postal rates to jump from 29 to 58 cents. The table below summarizes the doubling data, I have added a column for Consumer Price index (CPI) data as a reference.

July 1, 1885273.17.99
August 1, 1958473.128.9
May 16, 1971812.840.3
May 29, 1978157.064.5
February 3, 19912912.7134.8
August 29, 20215830.6273.57
Summary of First Class Postage Doubling Interval, 1885-2021

Now, any bets on the time it takes for postage to double from the 58-cent rate of 2021? My best guess is seven years since we just entered what looks to be another period of epic inflation.

Notes and Sources

[1] “John Wesley Powell, the noted geologist who explored the Colorado River, was honored on a 6-cent stamp issued August 1, 1969. Powell led an 1869 expedition down the Green and Colorado Rivers, a 1,000-mile, four-months’ journey.” Image and text from US Bureau of Engraving and Printing via Wikipedia accessed 25 July 2022

I should mention that the John Wesley Powell stamp made me realize I wanted to explore the Grand Canyon. I got my first look at the Grand Canyon, from he North Rim, in the summer of 1978. I have now hiked around and across many times. I still hope to raft the Colorado some day.

[2] The Consumer Price index (CPI) was 13.60 for July 1932. The CPI was 292.3 in May 2022. the ratio 292.3 / 13.6 is 21.5

Source U.S. Robert Shiller data set, Stock Markets 1871-Present and CAPE Ratio

[3] The Nixon quote is from Ryan Ellis, he provides a good description of the background behind the Postal Reorganization Act of 1970
The Birth of the USPS and the Politics of Postal Reform by Ryan Ellis accessed 25 July 2022

[4] Doubling the 8 cent rate of 1971 would require a 16 cent rate. I chose the closest rate of 15 cents in 1978, which isn’t quite double. I also chose 29 cents in 1991 as the next closest rate from 15 cents. While not perfectly accurate, I think they make the point.

Hydrogen Part 1 Today

Bill Gates wrote an insightful new blog post: “To cut emissions, use this Swiss Army Knife.” [1] He explains why hydrogen is essential now, how we might produce it without carbon dioxide, and why it may be more critical in our future. It’s worthwhile reading. My friend Christopher recently talked to me about future uses of hydrogen. Christopher and Bill Gates are both on to a good idea; they triggered me to start thinking more about hydrogen.

When I think about hydrogen, three things spring to mind: Lots of energy, easily made from water and electricity, and very dangerous. These were lessons I learned more than fifty years ago.

The energy available from hydrogen propelled the Apollo moon program. The Saturn V second and third-stage rockets used liquid hydrogen fuel; that was a lot of liquid hydrogen! I found that hydrogen was easy to make in my high school chemistry lab using electrolysis. The collected hydrogen would burn with a bit of pop.

I had seen proof of the dangers of hydrogen. A friend owned a melted piece of structural aluminum from the Hindenburg; this hydrogen-filled dirigible had burned while mooring in 1937. A more memorable use: the hydrogen-oxygen fuel cells on Apollo 13. The explosion of one of these fuel cells almost killed the crew and led to a remarkable space rescue effort. 

After reading Bill’s article and talking with my friend about the future of hydrogen, I decided it was time to upgrade my knowledge of hydrogen. I decided upon a four-part plan: How do we make hydrogen today? What are the current applications of hydrogen? How might we use hydrogen in the future? Finally, how would we produce hydrogen in the future? I divided this blog into two. The first part covers hydrogen production and application today; the second will address the future. My goal was to teach myself a bit more about hydrogen, and hopefully, it will interest readers.

So, how do we make industrial quantities of hydrogen today? I found an explanation from the Department of Energy of one method of making hydrogen. [2] Hydrogen is primarily made via a Steam-Methane Reforming reaction (SMR). Methane gas reacts with steam and heat to produce hydrogen and carbon monoxide:
CH4 + H2O (+ heat) → CO + 3H2
The remaining carbon monoxide reacts with steam in the Water-gas Shift (WGS) reaction. It produces more hydrogen and carbon dioxide:
CO + H2O → CO2 + H2 (+ heat)

Another method used to produce hydrogen is coal gasification. [3] In this process, oxygen combusts carbon in coal to produce carbon dioxide:
C + O2 → CO2 ( + heat)
The CO2 and heat react (gasification) to produce carbon monoxide:
C + CO2 (+ heat) → 2CO
The Water-gas Shift (WGS) reaction produces hydrogen and carbon dioxide:
CO + H2O → CO2 + H2 (+ heat)

In 2020, the world produced 70 million tons of hydrogen. According to the US Department of Energy, 76% of global hydrogen comes from the Steam-methane reforming reaction, 22% more from coal gasification, and 2% from electrolysis. [4]

Why change these processes? Bill Gates said that industrial hydrogen manufacture produces 1.6% of CO2 emissions. The  International Energy Agency (IEA) estimated that hydrogen generation would generate about 900 million tons of carbon dioxide in 2020. [5] Hydrogen produced from uncontrolled fossil fuels is referred to as “grey” hydrogen, as defined by researchers at Columbia University. [6]

I was surprised that petroleum refining is today’s most important use of hydrogen. The hydro-desulfurization reaction lowers the sulfur content of fossil fuels, thus using more than half the world’s hydrogen. The manufacture of ammonium nitrate fertilizer via the Haber process uses lots of hydrogen. Metal refining, chemicals  (acid, methanol, hydrogen peroxide), and hydrogenated oil food production also use hydrogen. [7]


[1] Gates, Bill. THE OTHER HYDRO POWER: To cut emissions, use this Swiss Army Knife. GatesNotes The Blog of Bill Gates, 21 June 2022.  Accessed 22 June 2022.

[2] US Department of Energy.  Hydrogen Production: Natural Gas Reforming. Accessed 22 June 2022. 

[3] Allen, Jessica. Explainer: how do we make hydrogen from coal, and is it really a clean fuel?, The Conversation website, 13 April 2018.  Accessed 25 June 2022.  

[4] US Department of Energy. Hydrogen Strategy, July, 2020. Accessed 22 June 2022.

[5] Bermudez, Jose M.; Hannula, Ikulla et. al. Hydrogen – More efforts needed. International Energy Agency, November, 2021. Accessed 25 June 2022. 

[6] Ochu, Emeka; Braverman, Sarah; Smith, Griffin; and Friedman, Julio. Hydrogen Fact Sheet: Production of Low-Carbon Hydrogen. Columbia University,  17 June 2021. Accessed 22 June 2022.

[7] Brown, Andy. Uses of Hydrogen in Industry. The Chemical Engineer, 16 July 2019. Accessed 25 June 2022. 

Life is better than ever for most of humanity.

Life is better than ever for most of humanity.

In 2019, I wrote a book review of “Enlightenment Now” by Stephen Pinker. I revisited this review in 2022. In these three years, I’ve experienced a worldwide pandemic, Russia at war with Ukraine, and domestic turmoil in the US. Despite the turbulent times, I still agree with Pinker. Here’s my review; this is a book worth reading.

Life is better than ever for most humanity; despite a barrage of media that paints a dismal picture of life on Earth. Most of society would agree with Barack Obama’s 2016 view “…. if you had to choose blindly what moment you’d want to be born, you’d choose now.” [1] In “Enlightenment Now,” Stephen Pinker provides a quantitative assessment of how life has improved throughout human history. He asserts:

“…. I will show that this bleak assessment of the state of the world is wrong. …. I will present a different understanding of the world, grounded in fact and inspired by the ideals of the Enlightenment: reason, science, humanism, and progress.” [2]

The book starts with three chapters that explain the Enlightenment, some basic science, and the counter-Enlightenment. The majority of the books, seventeen chapters, deal with progress in life, health, sustenance, wealth, inequality, the environment, peace, safety, terrorism, equal rights, knowledge, quality of life, and happiness. The final three chapters deal with reason, science, and humanism in our world.

First, Pinker asks: What is the Enlightenment? He starts with Immanuel Kant’s 1784 definition:

“Enlightenment is man’s release from his self-incurred immaturity. Immaturity is man’s inability to make use of his understanding without direction from another. This immaturity is self-imposed when its cause lies not in lack of reason but in lack of resolution and courage to use it without direction from another. Sapere aude! “Have courage to use your own reason!” — that is the motto of Enlightenment.” [3]

Of course, if the Enlightenment was so great, why aren’t all human problems solved? Pinker says:

“And if you’re committed to progress, you can’t very well claim to have it all figured out. It takes nothing away from the Enlightenment thinkers to identify some critical ideas about the human condition and the nature of progress that we know and they didn’t. Those ideas, I suggest, are entropy, evolution, and information.”

Pinker next explains entropy, evolution, and information. I found this chapter a bit hard to grasp. Perhaps my engineering background causes me to yearn for straightforward definitions. Let’s say that entropy is the tendency towards disorder (such as in my office), and energy is required to counteract entropy. A brief synopsis of Pinker’s description:

[Entropy] “Living things are made of organs that have heterogeneous parts which are uncannily shaped and arranged to do things that keep the organism alive (that is, continuing to absorb energy to resist entropy).”

[Evolution] “The replicating systems would compete for the material to make their copies and the energy to power the replication. Since no copying process is perfect—the Law of Entropy sees to that—errors will crop up, and though most of these mutations will degrade the replicator (entropy again), occasionally dumb luck will throw one up that’s more effective at replicating, and its descendants will swamp the competition.”

[Information] “Information may be thought of as a reduction in entropy—as the ingredient that distinguishes an orderly, structured system from the vast set of random, useless ones.” [4]

Here’s a summary of why we should care about entropy, evolution, and information:

“Getting back to evolution, a brain wired by information in the genome to perform computations on information coming in from the senses could organize the animal’s behavior in a way that allowed it to capture energy and resist entropy. …. Energy channeled by knowledge is the elixir with which we stave off entropy, and advances in energy capture are advances in human destiny.” [5]

Next chapter, there are some details of the counter-Enlightenment. Pinker provides four alternatives:

  1. Religious faith
  2. “People are the expendable cells of a superorganism .…”
  3. [declinism] “One form of declinism bemoans our Promethean dabbling with technology.”
  4. [scientism] “… the intrusion of science into the territory of the humanities ….

A summary of why the counter-Enlightenment should be transcended:

“Our greatest enemies are ultimately not our political adversaries but entropy, evolution (in the form of pestilence and the flaws in human nature), and most of all ignorance—a shortfall of knowledge of how best to solve our problems.” [6]

The majority of “Enlightenment Now” deals with progress in many areas of human life. Here are a few of my most significant findings from Pinker’s extensive research, supported by much data.

[Sustenance] “… in spite of burgeoning numbers, the developing world is feeding itself. Vulnerability to famine appears to have been virtually eradicated from all regions outside Africa.”. … “Famine as an endemic problem in Asia and Europe seems to have been consigned to history.”…

“Once the secrets to growing food in abundance are unlocked and the infrastructure to move it around is in place, the decline of famine depends on the decline of poverty, war, and autocracy.” [7]

[Wealth] “Among the brainchildren of the Enlightenment is the realization that wealth is created. It is created primarily by knowledge and cooperation: networks of people arrange matter into improbable but useful configurations and combine the fruits of their ingenuity and labor. The corollary, just as radical, is that we can figure out how to make more of it. …. “Also, technology doesn’t just improve old things; it invents new ones. How much did it cost in 1800 to purchase a refrigerator, a musical recording, a bicycle, a cell phone, Wikipedia, a photo of your child, a laptop and printer, a contraceptive pill, a dose of antibiotics? The answer is: no amount of money in the world. The combination of better products and new products makes it almost impossible to track material well-being across the decades and centuries. “[8]

[Inequality] “Inequality is not the same as poverty, and it is not a fundamental dimension of human flourishing.” … “As globalization and technology have lifted billions out of poverty and created a global middle class, international and global inequality have decreased, at the same time that they enrich elites whose analytical, creative, or financial impact has global reach. The fortunes of the lower classes in developed countries have not improved nearly as much, but they have improved….” [9]

[Environment] “The key idea is that environmental problems, like other problems, are solvable, given the right knowledge. …. humanity is not on an irrevocable path to ecological suicide.” “An enlightened environmentalism recognizes that humans need to use energy to lift themselves out of the poverty to which entropy and evolution consign them.” [10]

[Knowledge] “Homo sapiens, “knowing man,” is the species that uses information to resist the rot of entropy and the burdens of evolution. …. But some of the causal pathways vindicate the values of the Enlightenment. So much changes when you get an education!

• They are less racist, sexist, xenophobic, homophobic, and authoritarian.

• They place a higher value on imagination, independence, and free speech.

For all these reasons, the growth of education—and its first dividend, literacy—is a flagship of human progress.” [11]

[The Future of Progress] “Ever since the Enlightenment and the invention of science, we’ve managed to create a tiny bit more than we’ve destroyed each year. But that few percent positive difference is compounded over decades into what we might call civilization . . . . [progress] is a self-cloaking action seen only in retrospect. Which is why I tell people that my great optimism of the future is rooted in history.” Hans Rosling, who, when asked whether he was an optimist, replied, “I am not an optimist. I’m a very serious possibilist.” [12]

The final part of “Enlightenment Now” explains the importance of reason, science, and humanism. Pinker makes a strong case for using reason to understand the world. Here’s a brief selection of why reason matters:

  • “Making reason the currency of our discourse begins with clarity about the centrality of reason itself.”
  • “The human brain is capable of reason, given the right circumstances; the problem is to identify those circumstances and put them more firmly in place.”
  • “People understand concepts only when they are forced to think them through, to discuss them with others, and to use them to solve problems. A second impediment to effective teaching is that pupils don’t spontaneously transfer what they learned from one concrete example to others in the same abstract category.” [13]

Pinker advocates that science is the best tool humanity has to understand the world. Here is his explanation of what distinguishes science from other exercises of reason:

“All the methods are pressed into the service of two ideals, and it is these ideals that advocates of science want to export to the rest of intellectual life.

1. The first is that the world is intelligible.

2. The second ideal is that we must allow the world to tell us whether our ideas about it are correct.

When scientists are pressed to explain how they do this, they usually reach for Karl Popper’s model of conjecture and refutation, in which a scientific theory may be falsified by empirical tests but is never confirmed.” [14]

The book’s final chapter explains humanism, why it matters, and how it substitutes for religion in the modern world. Here are some of Pinker’s explanations of humanism:

  • “Spinoza: “Those who are governed by reason desire nothing for themselves which they do not also desire for the rest of humankind.” Progress consists of deploying knowledge to allow all of humankind to flourish in the same way that each of us seeks to flourish. The goal of maximizing human flourishing—life, health, happiness, freedom, knowledge, love, richness of experience—may be called humanism.”
  • “There is a growing movement called Humanism, which promotes a non-supernatural basis for meaning and ethics: good without God.” [15]

Pinker addresses many of the deficits of religion in this chapter. I can’t synopsize all his arguments, but here is one quote that stuck in my mind:

“To begin with, the alternative to “religion” as a source of meaning is not “science.” No one ever suggested that we look to ichthyology or nephrology for Enlightenment on how to live, but rather to the entire fabric of human knowledge, reason, and humanistic values, of which science is a part.” [16]

One issue I see is that current representations of human knowledge aren’t in a holistic framework that covers the “entire fabric of human knowledge” accessible to most humans. It would be helpful to have an accessible form of humanism, the closest that I’m aware of are Unitarian Universalists.

To summarize, “Enlightenment Now” makes a strong case, using data, references, and compelling explanations, that life is improving for most humans. As Pinker asserts: “As always, the only way to know which way the world is going is to quantify.” [17]

The author makes a strong case that reason and science are the root cause for the progress of human life across many dimensions. In contrast, while Pinker explains well the importance of humanism, in the end, I’m not sure how to truly put humanism into practice in my life and community. That said, “Enlightenment Now” is a profound and encouraging book. I agree with Pinker:

“We will never have a perfect world, and it would be dangerous to seek one. But there is no limit to the betterments we can attain if we continue to apply knowledge to enhance human flourishing.” [18]


[1] As quoted in “Enlightenment Now”, Part III
[2] “Enlightenment Now”, Preface.
[3] Kant, Immanuel. “An Answer to the Question: What is Enlightenment?” (Was ist
Äufklarung?), 30 September, 1784. Pinker translates the Latin “Sapere aude!” as “Dare to understand!” Instead of “Have courage to use your own reason!”
[4] “Enlightenment Now”, Chapter 2. I’d note that the majority of living things are single cell organisms but that doesn’t change Pinker’s observation.
[5] “Enlightenment Now”, Chapter 3.
[6] “Enlightenment Now”, Chapter 3.
[7] “Enlightenment Now”, Chapter 7.
[8] “Enlightenment Now”, Chapter 8.
[9] “Enlightenment Now”, Chapter 9.
[10] “Enlightenment Now”, Chapter 10.
[11] “Enlightenment Now”, Chapter 16.
[12] “Enlightenment Now”, Chapter 20.
[13] “Enlightenment Now”, Chapter 21.
[14] “Enlightenment Now”, Chapter 22.
[15] “Enlightenment Now”, Chapter 23.
[16] “Enlightenment Now”, Chapter 23.
[17] “Enlightenment Now”, Chapter 14.
[18] “Enlightenment Now”, Chapter 23.