Category Archives: fourfolds

The Four Immeasurables

May all beings have happiness and the causes of happiness.
May they be free of suffering and the causes of suffering.
May they never be separated from supreme joy beyond all sorrow.
May they abide in equanimity free from attachment and aversion.

— Buddhist Prayer

I’m currently watching a beautiful anime called “The Heike Story”, based on the Japanese Tale of the Heike. The central character is a child plagued with the ability to see visions (usually of death and destruction) of the future and remote events. She is anguished to witness  these and is powerless to do anything about them,  but finally (spoilers!) determines that she might ease her mind by praying for those involved.

This character is not portrayed as any sort of  religious individual, so I wondered what kind of prayer might be appropriate for her. Searching for an “Atheist Prayer”, I quickly found the Buddhist Prayer above that might be something like she would say, that encodes the “Four Immeasurables” of Buddhist thought. This prayer is not offered to any god or gods, but just a wish and hope for those in mind and indeed for all sentient beings.

The Four Immeasurables of Buddhism are

  • Maitri: Loving kindness
  • Karuna: Compassion
  • Mudita: Sympathetic Joy
  • Upeksha: Equanimity

Further Reading:

The Four Immeasurables


The Four Elements of Thinking

While searching for something else I chanced upon “The Four Elements of Thinking: Reasoning, Creativity, Synthesis, Evaluation” by Benjamin Cheung, Ph.D., published in 2019. Any book about the four classical elements being used as metaphors for other things is of personal interest, plus that the things being four aspects of thinking was immediately intriguing. Dr. Cheung divides thinking into the four aspects of the subtitle, plus he divides each aspect into four sub-aspects or skills as follows:

    • Reasoning (Earth Thinking)
      • Evidence
      • Inductive Reasoning
      • Deductive Reasoning
      • Abductive Reasoning
    • Creativity (Air Thinking)
      • Investigation
      • Incubation
      • Insight
      • Innovation
    • Synthesis (Water Thinking)
      • Linking
      • Perspective
      • Synthesis
      • Pivots
    • Evaluation (Fire Thinking)
      • Decisions
      • Judgments
      • Contingency Plans
      • Validation

Note his choice in assignment of the Classical Four Elements to each of these aspects of thinking. I would have assigned them differently: Reasoning to Fire, Creativity to Earth, Synthesis to Air, and Evaluation to Water. The price of the e-book is reasonable, so I may investigate the “thinking” behind his alignments by purchasing and reading further.

He also has an interesting book on collections of ideas which he arranges into a “periodic table,” which might be analogous to a more modern scientific elemental assignment. Additionally, he has had Kickstarters on playing or flash cards for both books, which is a notion somewhat dear to my heart (See A Game of Fourfolds).

I have mentioned thinking or thought often in this blog, and believe that poor thinking or irrational thinking is greatly to blame for many of our current ills. Blame can also be attributed to poor communication skills. The best thinking can be obscured by poor communication. What is the best theory of the linkage between thought and language?

Further Reading:

Benjamin Cheung, Ph. D. / The Four Elements of Thinking: Reasoning, Creativity, Synthesis, Evaluation

Link to Amazon



Maxwell Relations

Maxwell Relations are commonly known as a set of four partial differential equations between four thermodynamic quantities or potentials: pressure (P), volume (V), temperature (T), and entropy (S). So for example the expression (∂T/∂V) |S  means the partial derivative of T with respect to V while keeping S constant.

    • (∂T/∂V) |S = -(∂P/∂S) |V
    • (∂P/∂T) |V = (∂S/∂V) |T
    • -(∂S/∂P) |T = (∂V/∂T) |P
    • (∂V/∂S) |P = (∂T/∂P) |S

In my diagram above, the expressions that are equal are on either side of the common leg of adjacent isosceles right triangles.

Further Reading:

Thermodynamics and the Four Thermodynamic Potentials

[*12.194, *12.195]


Linear Process Algebra

One of computer scientist and Professor Emeritus Vaughan Pratt’s most recent conference papers is on “linear process algebra,” which relates several of his previous interests on linear logic, Chu spaces, concurrent processes, events and states, etc.

The paper opens with a nice overview of computer science research primarily concerned with concurrent processes. Computation itself divides into the aspects of logical and algorithmic, formal methods into the logical and algebraic, concurrent computation into operational and denotational, and then the author gives a brief list of models of processes by a variety of mathematical structures until he comes to his theme of using Chu spaces.

As an example, he presents processes as Chu spaces over the set K, where K = { 0, T, 1, X}, with names and meanings :

  • 0: Ready
  • T: Transition
  • 1: Done
  • X: Cancelled

and then details four binary operations as working in Chu spaces over K:

  • P ; Q: Sequence
  • P + Q: Choice
  • P || Q: Concurrence
  • P ⊗ Q: Orthocurrence

Further Reading:

Vaughan Pratt / Linear Process Algebra

Click to access bhub.pdf

Click to access lpa.pdf

Click to access bud.pdf



Neon Genesis Evangelion Rebuilt, V2

The fourth movie was finally made and finally shown! Thank you Hideaki Anno, for finishing your rebuild, and Amazon Prime, for letting us easily see all four.

Full of battles between giant robots and kaiju called angels, full of teenage, human, and non-human emotional struggles, and full of signature Evangelion nonsense, about midway I was getting a bit unhappy with it. But as it coming to a close I thought that this was indeed a good ending.

So what does “Thrice Upon a Time” mean? That this is the third ending? First for the series, second for the movies after the series, and thirdly for the rebuilt movies? And what does the designation “3.0+1.0” mean? Three movies plus one more?

Further Reading:

‘Evangelion: 3.0+1.0 Thrice Upon a Time’ Review: Hideaki Anno’s Iconic Anime Finally Gets a Proper Ending

Neon Genesis Evangelion Rebuilt




On the Death of a Giant

Renowned physicist Steven Weinberg passed away recently. He was a giant in the world of physics and winner of the Nobel prize, advancing knowledge about the Standard Model and the unification of physical forces. He was also, famously, a materialist and atheist.

In his book “The Sophist”, Plato wrote (metaphorically?) about the battle of the gods and the giants. He related how the gods were friends of Platonic forms (perhaps being close to forms themselves) whereas the giants were materialists. Plato, being partial to forms, painted the giants as militant and unreasonable materialists, and the gods as a friendly and peaceful sort.

The Greek gods were friendly and peaceful? Perhaps the giants of the legend were the easy-going and reasonable sort, since the gods of the Greeks seemed the opposite. They say that history is rewritten by the victors.

Further Reading:

With Steven Weinberg’s death, physics loses a titan

A very nice article:

Steven Weinberg (1933-2021): a personal view


John Buridan’s Octagon of Opposition

Medieval logician John (or Jean) Buridan was a scholar of Aristotle, and wrote many works of commentary and elaboration on Aristotelian philosophy. Several items in logic and philosophy are tied to Buridan (such as Buridan’s Bridge and Buridan’s Ass) but he may now be more widely known for his Octagon which combines Aristotle’s Square of Opposition with a Square of Modality.

Below and to the right is a fourfold diagram of Aristotle’s Square of Opposition. The modern universal and existential (or particular) qualifiers are ∀ (meaning All) and ∃ (meaning Some), respectively. Also in these diagrams, ¬ means logical Not.

  • ∀ S are P
  • ∃ S are P
  • ∀ S are ¬ P
  • ∃ S are ¬ P

Next I show a fourfold of modal operators and their equivalents. The modern modal symbols are (meaning Necessarily) and or ◊ (meaning Possibly).

  • P ≡ ¬ ◊ ¬ P
  • ◊ P ≡ ¬ ¬ P
  • ¬ P ≡ ◊ ¬ P
  • ¬ ◊ P ≡ ¬ P


Further Reading:

The Art of the Syllogism

Click to access Demey_DWMC2015_Buridan_Avicenna_slides.pdf

Click to access Buridan_Octagon.pdf

Click to access hughes-buridan.pdf





What am I?

I am the Beginning of Everything,
I am the End of Time and Space,
I am the Beginning of Every End,
and the End of Every Place.

What am I? (Hint: the answer isn’t Four!)

Further Reading:

Other images of this riddle are here.

Such riddles remind me of the Song of Amergin.




The Square of Epictetus

Here is a nice two-by-two matrix by engineer David E. Goldberg derived from the stoic philosophy of Epictetus. For each and every concern, it’s the cross product of one’s Activity (control vs. no control) and State of Mind (concerned vs. not concerned). And so we have the four combinations:

  • Concerned with Control: Accomplishment
  • Unconcerned with Control: Forgone Opportunity
  • Concerned but No Control: Needless Worry
  • Unconcerned and No Control: Peace of Mind

Of course the key is to dwell within the positive Accomplishment and Peace of Mind regions, and not to inhabit the negative ones of Needless Worry and Forgone Opportunity.

Further Reading:

More Accomplishment, Less Worry: Follow the Epictetus Square




The Four Worlds of the Kabbalah

The Kabbalah (correspondence) is a traditional and esoteric school of thought in Jewish mysticism. The ten Sephirot (emanations) of the Kabbalah in the Tree of Life diagram can be divided into Four Worlds as follows, and correspond with the Four Suits of the Tarot and the Four Elements:

  • Atziluth (אֲצִילוּת): World of Emanation (Wands, Fire, Spirit)
  • Beri’ah (בְּרִיאָה): World of Creation (Swords, Air, Intellect)
  • Yetzirah (יְצִירָה): World of Formation (Cups, Water, Emotion)
  • Asiyah (עֲשִׂיָה): World of Manifestion (Disks, Earth, Action)


Further Reading:


The Four Worlds