JP Castlin
@jpcastlin.bsky.social
Ex-lawyer strategy advisor + author. Discoverer of dynamic uncertainty, inventor of the 4E model of market dynamics, creator of frameworks, and PA of (a.k.a. father to) Idun and Edda. As seen on stage, on TV, in books, in newspapers, in columns, etc.
Is it a flock, or a single bird repeating its average behavior at the moment? Why, no - it is a newsletter on ergodicity!
The TL;DR
- Ergodicity ends when yesterday’s outcome changes tomorrow’s odds, which quietly breaks many assumptions in strategy.
The TL;DR
- Ergodicity ends when yesterday’s outcome changes tomorrow’s odds, which quietly breaks many assumptions in strategy.
The one on ergodicity
Are you a gambler or a gamble?
strategyinpraxis.substack.com
January 16, 2026 at 8:01 AM
Is it a flock, or a single bird repeating its average behavior at the moment? Why, no - it is a newsletter on ergodicity!
The TL;DR
- Ergodicity ends when yesterday’s outcome changes tomorrow’s odds, which quietly breaks many assumptions in strategy.
The TL;DR
- Ergodicity ends when yesterday’s outcome changes tomorrow’s odds, which quietly breaks many assumptions in strategy.
Is it a bird? Is it a plane? No, it is a newsletter on strategy, uncertainty, and time.
The TL;DR:
The obvious answers to one of strategy’s most important questions do not survive scrutiny; they are either too universal to be useful in practice or confuse outcomes with strategy itself.
The TL;DR:
The obvious answers to one of strategy’s most important questions do not survive scrutiny; they are either too universal to be useful in practice or confuse outcomes with strategy itself.
The one on time
And fundamental aspects of strategy
strategyinpraxis.substack.com
January 9, 2026 at 8:36 AM
Is it a bird? Is it a plane? No, it is a newsletter on strategy, uncertainty, and time.
The TL;DR:
The obvious answers to one of strategy’s most important questions do not survive scrutiny; they are either too universal to be useful in practice or confuse outcomes with strategy itself.
The TL;DR:
The obvious answers to one of strategy’s most important questions do not survive scrutiny; they are either too universal to be useful in practice or confuse outcomes with strategy itself.
Is it a shooting star? Is it fireworks? No, it is the first newsletter of the year!
Today, we discuss morality and ethics as tools with which to reduce perceived uncertainty, how organizations go wrong when they try to navigate the moral landscape, and what they ought to do instead.
Today, we discuss morality and ethics as tools with which to reduce perceived uncertainty, how organizations go wrong when they try to navigate the moral landscape, and what they ought to do instead.
The one on ethics and uncertainty
Slippery slopes and unintended consequences
strategyinpraxis.substack.com
January 2, 2026 at 8:44 AM
Is it a shooting star? Is it fireworks? No, it is the first newsletter of the year!
Today, we discuss morality and ethics as tools with which to reduce perceived uncertainty, how organizations go wrong when they try to navigate the moral landscape, and what they ought to do instead.
Today, we discuss morality and ethics as tools with which to reduce perceived uncertainty, how organizations go wrong when they try to navigate the moral landscape, and what they ought to do instead.
Is it a bunch of fireflies? Are those fireworks? No, it is the final free-for-all newsletter of 2025.
Today, we round off the year by looking back at the past twelve months and ahead to those that will come.
From the bottom of my heart, thank you for subscribing. 2026 will be better than ever.
Today, we round off the year by looking back at the past twelve months and ahead to those that will come.
From the bottom of my heart, thank you for subscribing. 2026 will be better than ever.
The one on 2025
And a look ahead to 2026
strategyinpraxis.substack.com
December 26, 2025 at 7:19 AM
Is it a bunch of fireflies? Are those fireworks? No, it is the final free-for-all newsletter of 2025.
Today, we round off the year by looking back at the past twelve months and ahead to those that will come.
From the bottom of my heart, thank you for subscribing. 2026 will be better than ever.
Today, we round off the year by looking back at the past twelve months and ahead to those that will come.
From the bottom of my heart, thank you for subscribing. 2026 will be better than ever.
Is a bird? Is it Rudolph? No, it is the annual free-for-all list of six books to read over the holidays, this time featuring recommendations from people such as Rory Sutherland, Jag Bhalla, and Doug Garnett.
As always, I hope that you will like it and have a great holiday!
As always, I hope that you will like it and have a great holiday!
The (annual) one on books
Just-in-time gift ideas
strategyinpraxis.substack.com
December 19, 2025 at 10:14 AM
Is a bird? Is it Rudolph? No, it is the annual free-for-all list of six books to read over the holidays, this time featuring recommendations from people such as Rory Sutherland, Jag Bhalla, and Doug Garnett.
As always, I hope that you will like it and have a great holiday!
As always, I hope that you will like it and have a great holiday!
Reposted by JP Castlin
The one on mental health.
The one to read if you haven’t.
The one to read if you haven’t.
Is it a bird? Is it Santa Claus? No, it is a thick newsletter on mental health challenges that strategists face + a very special offer that ends as the year does + the 2026 schedule.
Topic TL;DR:
Topic TL;DR:
The one on mental health
A brief off piste
strategyinpraxis.substack.com
December 13, 2025 at 10:14 AM
The one on mental health.
The one to read if you haven’t.
The one to read if you haven’t.
Is it a bird? Is it Santa Claus? No, it is a thick newsletter on mental health challenges that strategists face + a very special offer that ends as the year does + the 2026 schedule.
Topic TL;DR:
Topic TL;DR:
The one on mental health
A brief off piste
strategyinpraxis.substack.com
December 12, 2025 at 9:30 AM
Is it a bird? Is it Santa Claus? No, it is a thick newsletter on mental health challenges that strategists face + a very special offer that ends as the year does + the 2026 schedule.
Topic TL;DR:
Topic TL;DR:
Is it a bumblebee? Is it a really large bumblebee?
No, it is a newsletter on the importance of self-similarity in strategy.
The TL;DR:
No, it is a newsletter on the importance of self-similarity in strategy.
The TL;DR:
The one on fractality
Crucial yet overlooked
strategyinpraxis.substack.com
December 5, 2025 at 9:54 AM
Is it a bumblebee? Is it a really large bumblebee?
No, it is a newsletter on the importance of self-similarity in strategy.
The TL;DR:
No, it is a newsletter on the importance of self-similarity in strategy.
The TL;DR:
Is it a bird? Is it a plane? Well, what are you most biased to see?
In today’s free-for-all newsletter, I take a critical view on the branch of behavioral science that is often reduced to social media memes.
In today’s free-for-all newsletter, I take a critical view on the branch of behavioral science that is often reduced to social media memes.
The one on behavioral science
Well, part of it anyway.
strategyinpraxis.substack.com
November 28, 2025 at 9:45 AM
Is it a bird? Is it a plane? Well, what are you most biased to see?
In today’s free-for-all newsletter, I take a critical view on the branch of behavioral science that is often reduced to social media memes.
In today’s free-for-all newsletter, I take a critical view on the branch of behavioral science that is often reduced to social media memes.
Is it a condor? Is it a UFO? Well, it must be the latter, because we can’t really see what it is.
So here is today’s newsletter, featuring an analysis of Nvidia’s quarterly report and a first look at my new WeftPoints method, but not featuring a TL;DR.
So here is today’s newsletter, featuring an analysis of Nvidia’s quarterly report and a first look at my new WeftPoints method, but not featuring a TL;DR.
The (last) one on decision-making
A work in progress
strategyinpraxis.substack.com
November 21, 2025 at 9:01 AM
Is it a condor? Is it a UFO? Well, it must be the latter, because we can’t really see what it is.
So here is today’s newsletter, featuring an analysis of Nvidia’s quarterly report and a first look at my new WeftPoints method, but not featuring a TL;DR.
So here is today’s newsletter, featuring an analysis of Nvidia’s quarterly report and a first look at my new WeftPoints method, but not featuring a TL;DR.
Before you have kids, the concept of catching vomit with your hands does not really exist in your realm of imagination.
November 17, 2025 at 3:33 PM
Before you have kids, the concept of catching vomit with your hands does not really exist in your realm of imagination.
Is it a penguin with a jet pack? Is it a flying saucer? No, it is a newsletter on the essence of strategy!
The TL;DR:
The TL;DR:
The one about the essence of strategy
A one-week off piste
strategyinpraxis.substack.com
November 14, 2025 at 8:04 AM
Is it a penguin with a jet pack? Is it a flying saucer? No, it is a newsletter on the essence of strategy!
The TL;DR:
The TL;DR:
Reposted by JP Castlin
Scott Galloway is a raging misogynist and it’s good to see this piece actually grapple with the toxic worldview he pushes
What Did Men Do to Deserve This?
Changes in the economy and in the culture seem to have hit them hard. Scott Galloway believes they need an “aspirational vision of masculinity.”
www.newyorker.com
November 10, 2025 at 4:36 PM
Scott Galloway is a raging misogynist and it’s good to see this piece actually grapple with the toxic worldview he pushes
Oh, and I'm back writing columns for MarketingWeek. How about that?
www.marketingweek.com/brand-buildi...
www.marketingweek.com/brand-buildi...
Don’t confuse brand building for a measure of ROI
Marketers who see brand building as an end in itself are mistaking the work they do for the results it delivers.
www.marketingweek.com
November 7, 2025 at 9:32 AM
Oh, and I'm back writing columns for MarketingWeek. How about that?
www.marketingweek.com/brand-buildi...
www.marketingweek.com/brand-buildi...
Is it a bat? Is it a UFO? No, it is another newsletter on decision-making — this time on how to improve both quality and speed of movement by shifting from stage gates to guardrails.
The (fourth) on decision-making
Just one more
strategyinpraxis.substack.com
November 7, 2025 at 8:41 AM
Is it a bat? Is it a UFO? No, it is another newsletter on decision-making — this time on how to improve both quality and speed of movement by shifting from stage gates to guardrails.
One of these days, some poor marketer is going to discover Hotelling's law and end up hospitalized.
October 31, 2025 at 2:35 PM
One of these days, some poor marketer is going to discover Hotelling's law and end up hospitalized.
Is it a kite? Is it Superman? No, wait. It is a free-for-all newsletter on theory vs practice.
TL;DR:
TL;DR:
The one on theory vs practice
A free-for-all
strategyinpraxis.substack.com
October 31, 2025 at 9:02 AM
Is it a kite? Is it Superman? No, wait. It is a free-for-all newsletter on theory vs practice.
TL;DR:
TL;DR:
Is it a seagull? Is it a space ship? No, it is an analysis of the state of AI investments. Oh, and the actual newsletter: this week on Gary Klein’s RPD model for decision-making under uncertainty.
TL;DR:
TL;DR:
The (third) on decision-making
Introducing RPD
strategyinpraxis.substack.com
October 24, 2025 at 7:56 AM
Is it a seagull? Is it a space ship? No, it is an analysis of the state of AI investments. Oh, and the actual newsletter: this week on Gary Klein’s RPD model for decision-making under uncertainty.
TL;DR:
TL;DR:
Is it a bird? Is it a plane? No, it is the supply for popular demand: a free-for-all one off newsletter on writing and AI.
Is it doomed to constitute, as so many writers appear to believe, intellectual entropy?
strategyinpraxis.substack.com/p/the-only-o...
Is it doomed to constitute, as so many writers appear to believe, intellectual entropy?
strategyinpraxis.substack.com/p/the-only-o...
The (only) one writing and AI
A pause in the natural order of things
strategyinpraxis.substack.com
October 17, 2025 at 8:55 AM
Is it a bird? Is it a plane? No, it is the supply for popular demand: a free-for-all one off newsletter on writing and AI.
Is it doomed to constitute, as so many writers appear to believe, intellectual entropy?
strategyinpraxis.substack.com/p/the-only-o...
Is it doomed to constitute, as so many writers appear to believe, intellectual entropy?
strategyinpraxis.substack.com/p/the-only-o...
Is it a dragonfly? Is it a kite? We are still not quite sure. Oh, wait! It is another newsletter on uncertainty — this one on my own work.
The TL;DR:
The TL;DR:
The (second) one on decision-making
Enter dynamic uncertainty
strategyinpraxis.substack.com
October 10, 2025 at 7:49 AM
Is it a dragonfly? Is it a kite? We are still not quite sure. Oh, wait! It is another newsletter on uncertainty — this one on my own work.
The TL;DR:
The TL;DR:
Is it a bird? Is it a plane? We aren’t really sure. Oh, wait! It’s a free-for-all newsletter about decision-making under uncertainty! And the 2026 keynotes too!
TL;DR:
TL;DR:
The (first) one on decision-making
A free-for-all
strategyinpraxis.substack.com
October 3, 2025 at 7:49 AM
Is it a bird? Is it a plane? We aren’t really sure. Oh, wait! It’s a free-for-all newsletter about decision-making under uncertainty! And the 2026 keynotes too!
TL;DR:
TL;DR:
Is it a pterodactyl? Is it an airship? No, it’s the latest newsletter: the second on emergent strategy.
The (second) on emergent strategy
The Strategy Omnibus contined
strategyinpraxis.substack.com
September 19, 2025 at 7:42 AM
Is it a pterodactyl? Is it an airship? No, it’s the latest newsletter: the second on emergent strategy.
Is it a bird? Is it a plane? No, it is a free-for-all newsletter introducing emergent strategy.
The TL;DR:
The TL;DR:
The (first) one on emergent strategy
A free-for-all
strategyinpraxis.substack.com
September 12, 2025 at 7:46 AM
Is it a bird? Is it a plane? No, it is a free-for-all newsletter introducing emergent strategy.
The TL;DR:
The TL;DR:
Is it a bird, is it a plane? No, it is the last newsletter in our series on visioning and missioning.
TL;DR:
TL;DR:
The (final) one on visions
The pragmatic view
strategyinpraxis.substack.com
September 5, 2025 at 7:06 AM
Is it a bird, is it a plane? No, it is the last newsletter in our series on visioning and missioning.
TL;DR:
TL;DR:
Is it a bird, is it a plane?
No, it’s a free-for-all newsletter about visions and missions.
Enjoy.
strategyinpraxis.substack.com/p/the-first-...
No, it’s a free-for-all newsletter about visions and missions.
Enjoy.
strategyinpraxis.substack.com/p/the-first-...
The (first) one on visions
The Strategy Omnibus continued
strategyinpraxis.substack.com
August 22, 2025 at 8:23 AM
Is it a bird, is it a plane?
No, it’s a free-for-all newsletter about visions and missions.
Enjoy.
strategyinpraxis.substack.com/p/the-first-...
No, it’s a free-for-all newsletter about visions and missions.
Enjoy.
strategyinpraxis.substack.com/p/the-first-...