Professional scientist here. I would take a table of logarithms. In a world without computers, the logarithm table and slide rule are the essential tools of how things got built. We built the Golden Gate Bridge and put a man on the moon using nothing more than log tables.

Any one person can remember the gist of the scientific method and write it down on a page. To write down a quality logarithm table you would need 500 pages.

Resist the urge to fall in line behind a “strong man.” Once a community is beholden to an individual, it’s tainted.

The scientific method, we’ll be able to extract most information of the world around with just that and time

‘In the beginning the Universe was created.This had made many people very angry and has been widely regarded as a bad move.’

This exercise recurs regularly and there have been a few formulations.

One of the big ones is atomic theory. It took a long time to figure out - and I’m intentionally discounting the Greek version and monads here because I’m talking about actual atomic theory and not a philosophy of essences.

Darwinian evolution and Mendelian genetics are a second option, especially if you could squeeze in things like the germ theory of disease.

I’m not familiar enough with pure math to say that there’s one concept that would have let the Greeks or Mesopotamians develop the calculus millennia earlier than we did, but that would also massively accelerate scientific progress.

Brewing beer. It might not be “essential,” but the apocalypse is gonna be bad enough, might as well have beer.

• Crafting bows to hunt. Wood selection, shaping, tillering, natural bowstring materials.
• Some edible wild plants
• Some basic farming knowledge
• Some construction/shelter repair techniques
• Algebra and concepts of calculus, and why they’re useful
• How to preserve foods
• Basic concepts of electricity’s importance and how to make it, but someone would need to explain how to go from raw material to a functional wire, find some rare earth magnets, and figure out how to make LEDs or something else worth using the electricity for.
• The scientific method
• Concepts of how to engineer/design a solution to a problem
• Troubleshooting techniques
• Some basic concepts of boat stability and construction
• Some concepts of modern psychology
• Concepts of critical thinking and rejection of groupthink
• Basic physics. Loose explanations of kinematic equations, gravity, friction, pendulums, air resistance, aerodynamics, basic concepts of rocketry and flight/parachutes/gliders
• Evaporative cooling? I could describe the concepts of modern air conditioning, but that doesn’t seem useful yet.
• I could probably work out how a windmill works, how to make a wagon, how to purify water, how to make water-tight storage.
• Germ Theory
• The Paradox of Tolerance
• How pasteurization works
• Fermentation, concepts of distillation
• Basic oral hygiene? Habits of at least rinsing sugar out of your mouth afterwards, if brushes aren’t available.
• Use of alcohol and heat as antiseptics. Suggestion to use honey in a pinch
• Basic concepts of how magnifying lenses work and why they’re important

Basic system and web security might not seem important now, but let me tell you, if you adopt good cyber security practices early it will help you create a much more secure environment…

What’re you guys doing with those rocks?

I’m so far from an expert it’s not even funny but I’m a hobbyist for old valve (tube on the other side of the Atlantic) electronics. You need an industrial base to make semiconductors but if you can do flamework with glass and build a good enough pump that opens the door to amplifiers, radio, telecommunications, and even crude computers which in turn opens the door to a lot of creature comforts and social improvement that wouldn’t otherwise be possible.

I can’t help but feel soap making itself wouldn’t be as much use as why/when to use it?

Mixing oil with the ashy water (which is as simple as soap’s gonna get) is reasonably easy to do and so useful that even without a civilisation people would probably be doing it either through discovery or by keeping doing it?

I think things like “how to build a wooden bridge so it will hold a laden cart and not fall down” are more likely to be lost without civilisation while still being incredibly useful (although I can’t say I’d be very good for that)

I might add a section on refrigeration methods like zeers or wind towers/yakhchāls if the civilisation would be somewhere hot and dry, otherwise maybe something on using rivers for powering looms, mills etc.

The meaning of life is very very simple, love yourself and those around you as much as possible and have as much fun as you can. If it doesn’t hurt anyone or anything and you have fun doing it, do it a lot. When you genuinely love everyone around you, living becomes a lot easier and the meaning of life becomes simple.

Who’s ready to learn a lot about fermentation?!

I wonder if a book along these lines already exists. The nearest I can think of is The Art of Manliness website.

I would probably buy a book that covered a lot of the basic skills needed for a society if it were done well. I want to try a lot of those things like smelting, house construction, metalworking, etc. I’m sure books exist for each of these but I doubt one book tries to give overviews of all.

Also an interesting question: What ARE the skills needed for a civilization? Start from skills needed when dropped off alone in the wilderness and work your way up to “needing” bureuacrats.

All these tasty nutritious facts are great, but they’re doomed without a robust immune system.

They need to know how there’s a drunkard’s walk or one-way tropism for wealth and power to accumulate in the hands of the few, how the noblest intents get degraded and corrupted over time, how rich people get to make the rules and thereby get even richer, giving them even more control over the rules.

How this is what killed our civilisation in the first place, and how it will kill theirs if they let it. How you need to water the roots, not the leaves, unless you want the whole tree to collapse.

What rent-seeking looks like, how tribalism works, how propaganda and psyops and PR campaigns work, what narcissists and sociopaths are like, what abusive relationships look like (since they use the same tactics), how to spot demagogues, grifters and think-of-the-children paternalism. How internecine conflict is encouraged and used to distract from actual oppression. How the church maintained a vast grip on power for millennia just by manipulating shame, fear and self-righteousness.

How you can (and should!) make a bunch of rules to slow or mitigate this, but cancer finds a way; it will worm its way past your defenses in time. And when it does, you can’t fix it from within the system, pretty much by definition, because it subverts the law and the entire social contract to protect and serve itself.

How the only fix is to step outside the law, step outside the system and root it out the hard way, from the top down. You can’t put a formal trigger condition on this, as the failure mode will game its way round it: just say that when you need it, you’ll know.

Caring for animals in a humane way. Post apocolypse civilisation will be kind to our fluffy friends.