The Ladder
Every step lists what you need first, what it unlocks, how it can hurt you, and how to check it worked. Mark off what you have done and the ladder shows what you can start next.
0
Triage
Stop dying. Nothing else on this site matters until this tier is closed.
Energy used: about 5,000 kcal per person per day, Cook's hunting stage (100,000 BC) · where civilization stands
Binding constraint. The binding constraint is water and body heat, not food. You have roughly 3 days without water and 3 hours without shelter in a cold wind, against 3 weeks without food. Almost everyone who dies in the first month dies of dehydration, hypothermia, or a diarrhoeal infection from their own camp — not of starvation, and not of predators.
t0-water-find
Secure a source you can reach twice a day, forever, without a fight.
Water
Guide ×3BuildSheet ×2
t0-water-safe
Kill what is in the water before it kills you.
Water
Guide ×5BuildSheet ×2
70–100 °C
t0-fire
Make fire from nothing, then never make it from nothing again.
Energy
Guide ×3Sheet ×16
Up to ~600 °C in an open fire
t0-shelter
Get off the ground, out of the wind, and dry.
Shelter
Guide ×2Sheet ×11
t0-latrine
Break the faecal–oral route on day one, before habits form.
Water
Guide ×5BuildSheet
t0-camp
Place shelters, water, latrines and paths on the first day so that fire, flood and faecal disease cannot sweep the camp.
Settlements
Guide
t0-cut
Make something that cuts, and something that can make another one.
Tools
Guide ×3Sheet
t0-cord
Turn plant fibre into string, then string into rope.
Materials
Guide ×4Build ×2Sheet ×7
t0-food
Take calories out of the landscape while you wait for agriculture to start paying.
Food
Guide ×5Build ×2Sheet ×7
t0-firstaid
Stop bleeding, prevent infection, and set what is broken.
Health
Guide ×5
t0-seed
Protect the genetic capital that everything above this tier is built on.
Food
Guide ×5
t0-org
Agree the rule for making decisions, before you need to make a hard one.
Society
Guide
t0-record
Begin, on day one, the deliberate transfer of what you know to people who will outlive you.
Knowledge
1
Foothold
Convert from taking calories out of the landscape to putting them in. Stop moving.
Energy used: about 12,000 kcal per person per day, Cook's primitive agricultural stage (5000 BC) · where civilization stands
Binding constraint. The binding constraint is the first harvest. Between clearing ground and eating from it there is a gap of six to eighteen months during which the group is still living on foraged food while spending its labour on something that pays nothing yet. Groups fail here by planting too late, planting too little, or eating the seed stock in the hungry month before harvest.
t1-clear
Turn wild land into a field that does not lose its fertility in five years.
Food
Guide ×5BuildSheet
t1-preserve
Still be eating in March what you grew in August.
Food
Guide ×4Build ×2Sheet ×4
t1-nutrition
Keep a farming group from sickening on its own staple.
Health
Guide ×2
t1-teeth
Keep teeth through a starch-heavy diet, and recognise the dental infection that kills.
Health
t1-animals
Convert grass you cannot eat into food, fibre, fertiliser and power.
Food
Guide ×3Sheet ×2
t1-shelter
Build something that lasts thirty years, from what is under your feet.
Shelter
Guide ×3Build ×4Sheet ×11
t1-site
Settle where water lasts the dry season, floods cannot reach the floors, the ground drains and the wind carries smoke away.
Settlements
Guide ×2
t1-dwelling
Before the first footing is dug, a plan drawn to scale fixes where the fire and its smoke go, how many people sleep in each room, the wall weight for the climate, the house's turn to the winter sun, the overhang for its latitude, the openings for a through-draught, the floor height, and where the animals and the latrine stand.
Shelter
Guide
t1-pottery
Make a fire-proof, waterproof, permanent container — and learn to control temperature.
Materials
GuideBuild
600–1,000 °C
t1-textiles
Make cloth, so you are not dependent on hides.
Materials
Guide ×2BuildSheet ×2
t1-tanning
Turn raw hide into a material that does not rot.
Materials
Guide ×2BuildSheet
t1-midwifery
Stop losing mothers and infants to preventable causes.
Health
Guide ×2
t1-woodwork
Make things accurately from wood, including the machines that will later work metal.
Tools
Guide ×2Build ×2
t1-boats
Cross and work water without drowning — raft, dugout and paddle.
Transport
Guide ×2Build ×3Sheet ×9
t1-property
Establish who holds which ground, in a form that outlives the argument.
Society
Guide ×2
t1-commonworks
Build the thing everyone needs and nobody owns — and settle who pays for it.
Society
Guide ×2Sheet
t1-watch
Make the settlement hard to surprise, raid or burn — without starting a feud.
Society
Guide
2
Forge
Get above 1,100 °C and keep a written record. These two moves open more doors than everything below them combined.
Energy used: Bronze and Iron Age societies sit between Cook's primitive (12,000) and advanced (26,000) agricultural stages; he gives no figure for them. · where civilization stands
Binding constraint. The binding constraint is fuel, not ore. Bog iron and surface copper are common; sustained high temperature is not. A single bloomery smelt eats a stack of charcoal that takes a week to burn and a hectare of coppice to grow. Groups that skip charcoal and try to smelt with raw wood never reach temperature and conclude, wrongly, that they have no ore.
t2-charcoal
Make a fuel that burns hot enough to melt metal.
Energy
Guide ×5Build ×2Sheet ×16
Produces fuel capable of 1,200 °C+
t2-smelt
Extract metal from rock.
Materials
Guide ×6Build ×4Sheet
1,100–1,300 °C
t2-smith
Shape metal into tools — including the tools for shaping metal.
Tools
Guide ×2Build ×4Sheet
800–1,300 °C
t2-lime
Burn limestone and unlock mortar, plaster, flux, and disinfection.
Materials
Guide ×6Build ×2Sheet ×10
900 °C+
t2-brick
Make a standard, repeatable building unit — and something that will line a furnace.
Materials
Guide ×3Build ×3Sheet ×10
900–1,100 °C
t2-masonry
Walls of fired brick or stone in lime mortar, a roof that does not burn, and a chimney that takes every trace of smoke out of the house.
Shelter
GuideBuildSheet ×10
t2-barn
House the herd and its winter fodder so that the bedding stays dry, the air stays below the ammonia limit, the hay cannot burn the byre or the house, and nothing from either reaches the well or the people.
Shelter
Hay core: pull it apart at 66 °C; at 79 °C stop the air and call fire cover
Floor fall 1.5–2 % to the channel; ridge slot 5 cm per 3 m of building width
t2-writing
Move knowledge out of heads and onto something that outlives them.
Knowledge
t2-school
Build the institution that makes knowledge survive a death.
Knowledge
Guide
t2-wheel
Move heavy things further than you can carry them.
Transport
GuideBuild ×2
t2-plank-boats
Build boats of planks that carry a family and its goods, row them with oars sized by rule, and add a sail only to a boat that passes the stability test.
Transport
GuideBuildSheet ×8
t2-kites
Fly kites that carry a line across a river or a gorge, lift an aerial or a signal, and show how a surface held at an angle to the wind makes lift.
Transport
GuideBuildSheet ×5
t2-irrigate
Put water where the crop is, when the crop needs it.
Food
Guide ×5Sheet ×2
t2-fishpond
Grow a crop of fish in a fenced, drainable earthen pond that holds its water, keeps the dawn oxygen above the species' minimum, and is drained, harvested and dried each cycle.
Food
GuideBuild
Nile tilapia grow best at 27–30 °C and are in danger below 12 °C; common carp 23–26 °C
Secchi disc 40–60 cm; dawn oxygen above 3–4 mg/l
t2-brew
Put microbes to work — your first biotechnology.
Materials
Guide ×4Build
78 °C (ethanol boiling point)
t2-medicine
Build a small, honest pharmacopoeia from what grows locally.
Health
Guide
t2-numeracy
Make counting, measuring and reckoning ordinary rather than specialist.
Knowledge
Guide ×3
t2-writtenlaw
Put the rules where everyone can read them, and separate judging from ruling.
Society
Guide
t2-weights
Give every market a balance whose readings can be checked and a set of reference weights within published tolerances, held to a master by an office that verifies, stamps and re-inspects them.
Economy
Guide
Trade weights within OIML class M tolerances: 1 kg to ±50 mg (M1), ±160 mg (M2) or ±500 mg (M3)
t2-census
Count every person and dwelling as at one date, so that decisions about food, water, schools and shares start from a number rather than a guess.
Society
Guide
t2-plot
Lay out the settlement before it lays itself out.
Settlements
GuideBuild
3
Mill
Put something other than muscle to work, and start making machines that make machines.
Energy used: about 26,000 kcal per person per day, Cook's advanced agricultural stage (AD 1400) · where civilization stands
Binding constraint. The binding constraint is precision. A water wheel is easy; a water wheel driving a lathe that cuts a true cylinder is not. You cannot make a tool more accurate than the tool that made it — except through a handful of self-referential tricks, and until you know them you are stuck at the accuracy of your hands.
t3-waterpower
Get a source of continuous power that is not a muscle.
Energy
Guide ×4BuildSheet ×21
t3-windpower
Get continuous power where there is no falling water — which is most places.
Energy
Guide ×2BuildSheet ×23
t3-canals
Carry bulk goods by water where no river goes, and lift boats over hills.
Transport
Guide ×2Sheet ×7
t3-ships
Build and sail decked ships that cross open sea with cargo and crew, without capsizing, sinking or losing the crew to scurvy.
Transport
Guide ×2Sheet ×7
t3-balloons
Lift a load with heated air or a light gas, tether it for observation or signals, and know exactly how much it can carry and what makes it burn.
Transport
GuideBuildSheet ×5
t3-machinetools
Build machines that make machines — and break the accuracy ceiling.
Tools
Guide ×3Build ×3
0.1 mm → 0.01 mm
t3-steel
Make metal hard enough to cut other metal.
Materials
Guide ×2Build
900–1,100 °C
t3-cement
Make artificial stone you can pour into any shape.
Materials
Guide ×4BuildSheet ×10
1,400–1,450 °C
t3-glass
Make a transparent, chemically inert, formable solid.
Materials
Guide ×2Build ×2
1,100–1,500 °C
t3-glasshouse
Raise transplants before the last frost and keep tender crops growing after the first, under glass warmed by the sun, by rotting manure and by a wall that holds the day's heat.
Food
GuideBuild
Sow at 24 °C in the hotbed soil
t3-rotation
Run the fields as one system: a rotation whose fodder crops feed the stock and whose manure feeds the grain, wet land underdrained so it can be worked and sown, and grain drilled in rows at a known rate and depth so it can be counted and hoed.
Food
GuideSheet
t3-frame
Frame a building in timber on a masonry plinth, brace it so it cannot rack, glaze its windows, and keep it dry, warm and ventilated.
Shelter
Guide ×4Sheet ×10
t3-battery
Make a steady electric current from chemicals — for the telegraph, plating and electrolysis — before there is any generator.
Energy
Guide
Zinc boils at 907 °C; distil it at 1,100–1,200 °C
t3-germ
Establish that disease is caused by organisms — and act on it.
Health
Guide ×6Build
t3-chlorine
Make sodium hypochlorite from salt, water and direct current, measure its strength, and dose drinking water so that 0.2–0.5 mg/L of free chlorine remains 30 minutes later.
Water
Guide ×2Sheet
Brine 20–27 °C at the start; keep the cell below 35 °C
Free chlorine 0.2–0.5 mg/L at the collection point, 30 minutes after dosing
t3-instruments
Turn observation into numbers.
Knowledge
Guide ×5Build ×2
Repeatable to 1%
t3-units
Fix the units, hold the standards, and make every measurement comparable to every other.
Knowledge
Guide ×4
t3-method
Establish how you decide whether something is actually true.
Knowledge
Guide
t3-ledger
Keep accounts a stranger can check.
Economy
Guide ×2
t3-coin
Strike coins of a weight, fineness and size fixed in law, at one mint working under seal, and prove every year, in public, that they meet the standard.
Economy
Guide
Every coin within the weight, size and fineness limits the law sets, shown by the yearly public trial
t3-contract
Make a promise between strangers as reliable as one between kin, by writing it down and having a court enforce it quickly and cheaply.
Society
Guide
t3-publichealth
Give someone the standing, the information and the power to act on disease before it spreads.
Society
Guide ×5
t3-fire
Write and enforce a building code that stops a fire in one building from reaching the next, gets everyone out of the building it starts in, and puts enough water within reach of every building.
Settlements
Guide
Party wall at least 375 mm above the roof; escape window at least 0.33 m² and 450 × 450 mm
4
Engine
Burn stored sunlight instead of current sunlight. Break the land-area limit on energy.
Energy used: about 77,000 kcal per person per day, Cook's industrial stage (AD 1875) · where civilization stands
Binding constraint. The binding constraint is concentrated fuel and the pressure vessel that survives it. Coal and coke are worth nothing without boiler plate that will not split, which needs rolling mills, which need steam. The bootstrap out of this circle is small, low-pressure, and made of the best wrought iron you can forge by hand.
t4-coal
Break the land-area limit on energy.
Energy
Guide ×2Sheet ×16
Coke supports 1,600 °C+
t4-blast
Make iron by the tonne instead of by the kilogram.
Materials
Guide
1,500–2,000 °C
t4-steam
Turn heat into motion, anywhere you want it.
Energy
Guide ×3Sheet ×16
Bore round and parallel within ~0.5 mm
t4-factory
Make many identical things, and make them repairable.
Tools
Guide
Held to specified tolerance, not fitted
t4-steamships
Drive ships by steam against wind and current, build them of iron and steel, and stop them being overloaded or blown up by their own boilers.
Transport
GuideSheet ×7
t4-gliders
Design wings from measured data, make a glider stable and controllable in all three axes, and prove it with models, a wind tunnel and unmanned tests before anyone rides it.
Transport
GuideBuild ×2Sheet ×6
t4-cold
Hold food and medicine at a set cold temperature, all year, anywhere.
Food
Guide
2–8 °C held; −18 °C for frozen food
t4-anaesthesia
Make surgery survivable and therefore worth attempting.
Health
Guide ×2
t4-journal
Make disclosing what you know the self-interested move.
Knowledge
Guide
t4-university
Found universities that hold knowledge beyond any one teacher's lifetime: self-governing, free to teach and publish, examining to standards checked from outside, and reviewed by an independent agency.
Knowledge
Guide
t4-lab
Run laboratories whose results can be trusted and reconstructed after the investigator has gone: written procedures, calibrated instruments, raw data recorded and archived, quality checked by people independent of the work, hazards controlled by assessment, and competence proven to an outside body.
Knowledge
Guide
t4-credit
Move purchasing power across time, and survive the moment everyone wants it back at once.
Economy
Guide
t4-company
Let anyone form a company by registering it, let thousands of people invest in it while risking only what they put in, and pay for that protection with a public register, audited accounts and a board bound by duties to the shareholders.
Economy
Guide
t4-registry
Keep one public, durable record of who owns which land, who was born and who died, and which companies exist and who controls them.
Society
Guide
t4-service
Run each public function through a department with one written mandate, staffed by officials hired on merit who serve whoever is lawfully in charge.
Society
Guide
t4-zoning
Every parcel has a published zone, every odour, dust or major-hazard works stands at least its separation distance from homes and downwind and downstream of them, no home stands in the functional floodplain, and no hazardous-substance store stands in the 1 % flood zone.
Settlements
Guide ×2
t4-ironframe
Raise buildings of three storeys and more on iron columns, iron or steel beams and brick walls, with every load traced to the ground, cast iron used only where it is squeezed, walls no more slender than the code allows, and the iron protected from fire.
Shelter
Guide
5
Current
Move energy without moving matter, and break the nitrogen limit on food.
Energy used: about 230,000 kcal per person per day, Cook's technological stage (AD 1970) · where civilization stands
Binding constraint. The binding constraint is copper, insulation, and clean chemistry. Electricity is conceptually simple and materially demanding: it needs drawn wire in quantity, an insulator that does not fail wet, and — for anything past lighting — sulphuric acid at industrial scale. Haber-Bosch, which decides how many people you can feed, needs high pressure and a catalyst, and is the single hardest process on this site.
t5-generator
Convert motion into electricity, and electricity back into motion.
Energy
Guide ×4Sheet ×21
t5-electrochem
Use electricity to do chemistry that heat cannot.
Materials
Guide ×2Sheet ×6
t5-oil
Get a liquid fuel — dense, portable and pourable.
Energy
GuideSheet ×16
Fractions from 40 °C to 400 °C
t5-engine
Put a compact engine in a vehicle.
Transport
Bore and piston within ~0.02 mm
t5-aeroplane
Add an engine and propellers to a controllable airframe, keep weight and balance inside limits, and fly only proven, inspected designs with trained pilots.
Transport
GuideSheet ×7
t5-submarines
Take a hull under water and bring it back: trim it with ballast, build it for the pressure at its depth, and dive only a classed, tested design with a trained crew.
Transport
Sheet
t5-haber
Pull fertiliser out of the air.
Materials
Guide
400–500 °C at 150–300 atmospheres
t5-greenhouse
Hold the crop's temperature, humidity, light and carbon dioxide within range all year, at a heating and cooling cost worked out before the house is built.
Food
GuideBuild ×2
Crop air 17–27 °C; below 10 °C or above 35 °C most crops stop
t5-hydroponics
Grow greenhouse crops with their roots in a flowing nutrient solution or an inert substrate, with the solution's strength, acidity and oxygen measured every day and held in the crop's range.
Food
GuideBuild
Air for lettuce about 24 °C by day and 18 °C at night
EC and pH read every day; NFT channels at 1.2–3.0 % fall with no dips
t5-concrete
Build frames of reinforced concrete or steel, or confined masonry, that carry their loads with the steel where the tension is, the concrete mix, cover and curing the exposure needs, and the earthquake detailing the region needs, each stage inspected before it is hidden.
Shelter
Guide
Keep fresh concrete damp for at least 7 days; structural steel keeps about 60 % of its strength at 550 °C
Cover to the bars within the drawing's figure; hoops 75–100 mm apart in earthquake zones
t5-rights
Put the rules that bind the rule-makers into a supreme, published law that they cannot change alone and that courts enforce against them.
Society
Guide
t5-citizen
Give every person one place to get any public service, with published requirements, fee and deadline, and someone independent to complain to.
Society
Guide
t5-monetary
Measure the price level every month, give an independent central bank a published inflation target and the tools to meet it, and make banks safe enough that a run on one does not become a run on all.
Economy
Guide
Inflation held close to a published target, such as 2 % a year
t5-statistics
Draw samples at random, state the uncertainty of every estimate, fix the plan before the data arrive, read significance tests for what they are, and believe a finding only when it has been replicated.
Knowledge
Guide
t5-press
Let anyone publish without a licence, protect what they publish from punishment for criticising the powerful, keep the media many and independent, protect journalists and their sources, and hold the press to correcting its own errors.
Knowledge
t5-drip
Put each crop's water at its roots through pipes, in the amount the crop uses, when the soil says it needs it, with every emitter on a line delivering within 10 % of the others.
Food
GuideBuildSheet
Emitter flows within 10 % of each other along a line; pressure within 20 %
t5-city
Before the city reaches its fringe, reserve the land it will need for 20–30 years, secure an arterial grid about 1 km apart with its rights-of-way, lay a street hierarchy and utility corridors inside it, and publish the plan.
Settlements
Guide ×2
6
Logic
Make matter that computes. Stop paying for every copy of a thing you know.
Energy used: about 230,000 kcal per person per day, Cook's technological stage (AD 1970) · where civilization stands
Binding constraint. The binding constraint is purity and cleanliness, not cleverness. Semiconductor silicon must be 99.9999999% pure — nine nines — and worked in air cleaner than an operating theatre. Every step is understood; none is achievable by a workshop. This tier cannot be reached by a village, however skilled, and that is the honest answer.
t6-electronics
Control a large current with a small one.
Computing
Guide ×4Sheet
t6-semiconductor
Make matter with controllable conductivity — the hardest thing on this site.
Computing
Guide
Nine-nines purity; sub-micron features
t6-jets
Understand the gas turbine, the pressurised cabin, the helicopter and the air traffic system that let aircraft fly high, fast and safely in crowded skies.
Transport
GuideSheet ×9
t6-accountability
Give the public numbers it can trust about what government spends and achieves, produced and checked by offices the government cannot instruct.
Society
Guide ×2
t6-greenrev
Breed and supply short-strawed, high-yielding cereal varieties with the fertilizer and water they need, and pay their known costs up front: metered groundwater, no highly hazardous pesticides, a gene bank for the varieties they replace, and nutrients bred back into the staples.
Food
Guide ×2Sheet
7
Frontier
Reach the point you started from — then decide, deliberately, what to do differently.
Energy used: about 230,000 kcal per person per day, Cook's technological stage (AD 1970) · where civilization stands
Binding constraint. The binding constraint is no longer technical. Everything in this tier is a choice about coordination, incentives and time horizons. The failure modes are institutional: extraction outrunning replacement, knowledge held privately, and short-term decisions with century-long consequences.
t7-energy
Reach an industrial energy supply that does not have to be paid for twice.
Energy
Guide ×5Sheet ×21
t7-shipping
Move the world's goods by sea safely and with falling emissions, and build and equip small boats to the standards that keep their crews alive.
Transport
Guide ×2Sheet ×11
t7-aviation
Fly people and goods with the safety of today's airlines, fly drones within the rules, and cut aviation's emissions.
Transport
GuideSheet ×8
t7-institutions
Build the machinery that makes the other steps hold.
Society
Guide
t7-choose
Use the one genuine advantage a second attempt has: hindsight.
Society
Guide ×2
t7-cea
Grow leafy greens, herbs and transplants on stacked tiers under electric light, with the electricity per kilogram worked out before building, and the room held safe for the people working in it.
Food
Guide
Lettuce about 24 °C by day and 18 °C at night
Light, temperature, humidity and CO₂ logged and held to set points around the clock
t7-farming
Raise yields on the land already farmed while cutting the nitrogen, water, methane and soil each tonne costs, and stop losing the harvest after it is grown, each change measured on the farm.
Food
GuideSheet
t7-city
Build and renew neighbourhoods to UN-Habitat's five principles, with public transport and open space within a short walk of everyone, and plan, measure and report disaster risk against the Sendai Framework's targets.
Settlements
Guide