The Things We Make

Have you ever stopped to wonder how humanity built cathedrals long before anyone understood calculus or the science of materials? In The Things We Make, engineer and educator Bill Hammack argues that what makes this possible—and what continues to shape every technology around us—is not science or mathematics alone, but a distinct mode of thinking: the engineering method. He contends that from medieval masons to modern innovators, the true engine of progress is the use of rules of thumb—experience-based heuristics that enable creation even amid uncertainty.

Hammack’s central claim is deceptively simple: engineers solve problems with incomplete information using practical judgment rather than perfect knowledge. Their genius lies not in applying known science, but in working at the margins of the unknown to make functional solutions that fit the materials, energy, and cultural values of their time. Through vivid historical storytelling—from the medieval cathedrals of France to the light bulb wars of the 19th century and the microwave oven’s accidental rise after World War II—Hammack unveils the invisible method that binds centuries of human creativity.

Engineering vs. Science

The book begins with a striking comparison between the scientific method and the engineering method. While science seeks universal truths, engineering seeks usable solutions. Scientists ask “Why does it behave this way?”; engineers ask “How do we make it work?” In Sainte-Chapelle cathedral, 13th-century craftsmen built soaring arches without modern mathematics, relying instead on proportion rules passed orally from mason to mason. Hammack uses this to challenge the common notion that technology is simply "applied science." Instead, engineering operates as an independent philosophy—one that predates scientific theory and continues to thrive by embracing imperfection.

The Rule of Thumb Revolution

He calls these guiding principles “rules of thumb,” or heuristics—shortcuts that turn intractable problems into solvable ones. A head mason once sized cathedral walls using only a rope divided in thirds, transforming intuition into a physical design language. Modern engineers do the same, using simplified estimation methods to handle complex systems. These “rules” don’t guarantee exact results; they are flexible, contradictory, and context-bound. Yet when combined, they build skyscrapers, power grids, and spacecraft. Hammack’s insight here mirrors psychologist Gerd Gigerenzer’s defense of heuristics as powerful tools for decision-making under uncertainty—proof that imperfect knowledge can still yield brilliant outcomes.

Creativity and Failure as Method

Hammack reframes failure as the beating heart of engineering. From Josiah Wedgwood’s thousands of ceramic experiments to Edison’s endless trials with filaments, progress unfolds not by discovery alone but through iteration and adaptation. He highlights trial and error as one of three core strategies of the engineering mindset, alongside building on prior knowledge and negotiating trade-offs. Understanding why something fails is as important as why something works—because each failure sharpens intuition about what the next success might look like. (Historians like Henry Petroski, author of To Engineer Is Human, echo this idea: that engineering excellence grows through the disciplined study of flaws.)

Culture, Bias, and “Best” Design

When Hammack turns to design, he asks what “best” truly means. The Egyptian wine press and the Amazonian tipití—a woven Manioc squeezer—were each “best” within their cultures because they balanced local materials, labor, and needs. There is no universal best, only solutions shaped by context. He connects this to modern bias in design—from crash-test dummies modeled on men to algorithms optimized for average users—showing that every product embeds cultural values. The engineering method’s flexibility allows us to recognize and correct these blind spots, advocating for diversity as a way to expand the pool of available heuristics. More diverse perspectives mean more adaptive engineering.

From Uncertainty to Innovation

The engineering method’s true power lies in thriving amid uncertainty. Hammack tells of Osborne Reynolds visualizing turbulent flow with dye and smoke rather than waiting for complete scientific models—a story mirrored centuries later in Frances Arnold’s Nobel-winning work simulating biological evolution to create new enzymes. These examples reveal how engineers operate at the frontier of partly known phenomena, using intuition and iteration to achieve results before scientists can fully explain them. In this sense, engineering drives science forward rather than following it.

Technology as Moral Creation

Finally, Hammack situates engineering within ethics and human purpose. The microwave oven, born from wartime radar technology, became both a household convenience and a reflection of gendered labor divisions. It captures how technology reshapes society’s expectations—and how engineers must consider culture and morality alongside utility. Technology, he argues, isn’t a neutral force; it is a mirror of our choices. Understanding the engineering method empowers us to guide innovation responsibly, using simplicity and creative pragmatism not just to make things, but to make them right.

Across history’s cathedrals, turbines, ceramics, and electronics, Hammack exposes the invisible scaffolding of human ingenuity. His message is hopeful and practical: you don’t need perfect knowledge to change the world—only curiosity, resourcefulness, and the courage to work with what you have. The engineering method is not just how we build things; it’s how we build possibility itself.

Imagine trying to construct a cathedral with only a length of rope, a compass, and your intuition. In the thirteenth century, head masons did exactly that. Bill Hammack uses this scene to reveal the core mechanism of engineering: the rule of thumb. These heuristics—simple, empirically based shortcuts—are the invisible code that allows engineers to act under uncertainty. They substitute elaborate theory with practical wisdom, forming a universal toolkit across cultures and ages.

What Makes a Rule of Thumb Work

According to Hammack, a rule of thumb has four defining characteristics: it simplifies complex problems, offers a probable (not guaranteed) success, coexists with contradictory rules, and rejects absolutes. Like a chess player learning to “control the center of the board,” engineers learn that the point isn’t perfection—it’s improved odds. These rules are grounded in tense negotiation between intuition and experience. For medieval masons, the rule “make the wall one-fifth as thick as the arch’s span” ensured stability without mathematical calculation. For Niels Christensen, inventor of the O-ring, “cut the groove one and a half times the O-ring radius” emerged after forty years of tinkering. Both were creative acts of simplification that turned unknowns into usable guidance.

Heuristics vs. Science

A rule of thumb differs fundamentally from scientific law. Science eliminates old truths when new evidence appears—Einstein’s relativity displaced Newton’s mechanics. Engineering, however, keeps old heuristics alive until materials or context render them obsolete. Gothic masons’ rules didn’t fail—they simply disappeared when builders switched from stone to steel. Hammack argues that the engineering method is pragmatic, not theoretical—it judges success by outcomes, not proofs. (This resonates with philosopher Karl Popper’s distinction between justification and falsification.)

Rules for Creativity

The magic of these rules is their ability to inspire creativity. They act as scaffolds for improvisation. Engineers combine and mutate rules as artists mix colors or musicians bend tempo. Hammack calls this pattern “weaving heuristics”—engineers synthesize partial truths, contradictions, and practical constraints into designs that work. The ability to trust intuition grounded in evidence is what gives engineering its uniquely human flavor. As he puts it, every tool or structure “carries within it centuries of oral tradition, refinement, and rediscovery.” To learn a rule is to inherit humanity’s collective trial and error.

By demystifying these informal algorithms, Hammack invites you to see engineering not as rigid calculation but as living art—an art of reasoned improvisation that transforms imperfect information into enduring achievements.

What does “best” really mean when designing something? According to Hammack, engineers never aim for perfection—they aim for balance. The engineering meaning of best is always contextual: what works best given specific resources, constraints, and cultural values. This relativism runs through examples from Egyptian wine presses to Amazonian food technology, revealing an often-overlooked truth—solutions are cultural, not absolute.

Best Is Relative, Not Universal

In ancient Egypt, wine was pressed with linen sacks twisted by five workers; in the Amazon, the Arawak squeezed poisonous manioc in a woven tipití operated by one person. Each method was “best” for its time and place: Egypt’s labor surplus allowed inefficient teamwork, while the Arawak’s dispersed households demanded labor-saving ingenuity. The materials, weaving skills, and ecology dictated fitness, not ideals. Hammack shows that engineers pursue the “best all things considered”, not the best in theory. Their success is measured by harmony with context, not by universal performance metrics.

Bias and Blind Spots

Hammack exposes how this idea of best can be distorted by cultural bias. The Kodachrome color film optimized for pale skin, crash test dummies built for average men, and thermostats calibrated for male metabolism are examples of “best” constrained by exclusion. Technology, when defined by narrow parameters, fails entire groups. The antidote is diversity—since engineers draw from lived experience, expanding representation expands what counts as optimal. Georgena Terry’s redesign of bicycles for women demonstrates this perfectly: she shortened the frame and altered handle spacing to fit women’s anatomy, creating a ride described by customers with gratitude “from the bottom of my butt.”

Inclusive Engineering and Its Promise

From universal design guidelines like lower cabinets and D-shaped handles to voice recognition tuned for all accents, the modern ideal of best is evolving. Hammack sees “best” as dynamic—a moral as well as technical challenge. Engineers must question not only what performs well but for whom it performs. The engineering method’s adaptability makes equity possible because it welcomes refinement. By broadening participation, we expand the heuristic pool—and therefore our capacity to create solutions that serve everyone.

When you think of “best,” Hammack urges, think not of ideal forms but of realistic grace—the solution that fits its world responsibly. Engineering teaches us that even imperfection can be noble when molded in awareness of others.

If science demands control, engineering thrives in chaos. In one of the book’s most fascinating stories, Hammack invites you to look at a simple faucet. The transition from clear, smooth flow to turbulent gush is still not fully understood scientifically. Yet engineers built airplanes, ships, and aqueducts long before they could explain turbulence. How? By transforming uncertainty into guidance.

Osborne Reynolds and the Flow Mystery

In the 19th century, Reynolds filled a tank with water and injected dye to visualize how laminar flow turned turbulent. He discovered a threshold—what became known as the Reynolds number—marking the point where smooth motion collapses into chaotic eddies. His brilliance wasn’t in solving turbulence, but in describing it phenomenologically, bundling the complex variables (viscosity, velocity, and pipe diameter) into one usable ratio. This heuristic let engineers design ships and pipelines safely without waiting for perfect theory. That’s Hammack’s big takeaway: uncertainty isn’t the enemy; it’s the playground.

From Ethernet to Evolution

Jumping to the digital age, Bob Metcalfe’s invention of Ethernet echoed Reynolds’s genius. He resolved unpredictable network collisions by adding randomness—computers waited random intervals before resending data. What might look chaotic became stability through probability. Similarly, Nobel laureate Frances Arnold applied directed evolution to engineer enzymes, accepting that she couldn’t predict which mutations would succeed. By iterating and selecting improvements, she converted biological uncertainty into industrial chemistry breakthroughs.

Why Uncertainty Frees Imagination

Hammack’s philosophy reframes ignorance as liberation. When you stop expecting certainty, you open room for creativity. Every great innovation—from turbulence modeling to computer networking to biotechnology—emerges from leaning into unknowns. Engineers, by training, build fences around confusion then climb over them using heuristics and imagination. Understanding this teaches that real progress isn't about eliminating uncertainty but navigating it.

To Hammack, uncertainty is not a gap to be feared; it’s a frontier to be explored. In life as in engineering, the unknown doesn’t paralyze—it invites design.

A Mesopotamian trader’s wine shipment, an Islamic clockmaker’s candle contraption, and a rocket scientist’s satellite engine might seem worlds apart—but Hammack shows they share the same foundation: innovation shaped by available resources. Materials, energy, and knowledge form the triad that has always limited and inspired engineering creativity.

Material Constraints Create Ingenuity

Sidqum-Lanasi’s disposable wine rafts, or keleks, were made of wood bound by goat skins because the Euphrates’ rapids made permanent boats impractical. Lack dictated design: abundant timber up north allowed disposable building; scarce wood in Mari demanded selling it after each voyage. Similarly, Josiah Wedgwood’s ceramics used barium and clay—available mixtures—to produce the fine jasperware that rivaled porcelain. Engineers adapt materials to their local abundance and purpose, turning deficiency into advantage.

Energy Shapes Design

From al-Jazari’s 12th-century candle clock to nuclear submarines powered by steam turbines, Hammack shows how energy type transforms form. Al-Jazari’s clock regulated time by gravity and flame—a mechanical symphony of weight and combustion. Replace the candle with electricity, and the whole design shifts. Energy isn’t just fuel—it defines the rhythm and geometry of technology. As we rethink renewable sources today, Hammack reminds us that changing energy means rewriting design itself, not swapping a motor.

Knowledge as Resource

The third resource—knowledge—is both material and mental. Yvonne Brill’s dual-thrust satellite engine used hydrazine fuel efficiently because she combined decades of experience with intuitive chemistry. Her story also highlights another lesson: knowledge expands when excluded voices contribute. Brill’s career, interrupted by gender bias, underscores Hammack’s argument that diversity isn’t charity—it’s efficiency. Every added perspective increases our toolkit of rules of thumb, accelerating progress.

By tracing resources through history, Hammack reveals how scarcity catalyzes creativity. Engineering isn’t limited by what’s missing—it’s defined by what’s available, and more profoundly, by how imaginatively we use it.

Josiah Wedgwood’s laboratory under his mansion was a crucible of frustration and invention. His quest to make perfect ceramics mirrors the mental architecture Hammack calls the engineering mindset, built on three interlocking strategies: trial and error, building on past knowledge, and embracing trade-offs. These aren’t just techniques—they’re attitudes toward reality itself.

Trial and Error as an Engine

Wedgwood failed hundreds of times mixing clay formulas before inventing jasperware. His failures weren’t wasted—they refined intuition. Like Charles Parsons testing steam turbines or Frances Arnold mutating enzymes, engineers learn through systematic tinkering. Hammack contrasts this “guided failure” with random guessing; it’s empirical, deliberate, and cumulative. Over time, trial and error creates not just better products but sharper instinct—a feedback loop where failure breeds wisdom.

Past Knowledge as Guardrail

Engineers are conservative innovators. They respect tradition, not out of rigidity, but to avoid catastrophe. Hammack describes engineers as metaphorical gardeners—they cultivate what works already and tweak it carefully. Wedgwood studied old porcelain recipes before improvising improvements. This “incremental creativity” makes progress stable rather than reckless, ensuring bridges don’t collapse or satellites don’t fail mid-orbit.

Trade-Offs: The Art of Balance

Finally, Wedgwood’s breakthrough came when he accepted compromise. His dipped vases balanced coarse strength and fine beauty, embodying engineering’s core principle: every design involves competing demands. Hammack uses the soda can’s shape to illustrate this—neither cube (space-efficient) nor sphere (strongest), but a balance between usability and efficiency. Trade-offs define engineering’s maturity. Perfection isn’t possible; harmony is.

The engineering mindset, Hammack insists, isn’t a formula—it’s a philosophy of engagement with imperfection. To build anything lasting, you must experiment boldly, learn humbly, and compromise wisely.

If the engineering method predates science, how do science and math fit into it today? Hammack answers with two intertwined stories—the invention of Parsons’s turbine and the rise of risk mathematics. Both reveal that science and math are the gold standard for rules of thumb—extraordinarily powerful, yet still servants of engineering, not its masters.

Charles Parsons and Physics in Motion

Parsons built the first steam turbine by applying the data of physicists—Henri-Victor Regnault’s tables of steam and William Rankine’s calculations of nozzle velocity. These scientific constants allowed him to estimate pressures and blade spacing without guesswork. But science didn’t design the turbine; Parsons did. He interpreted data imaginatively, turning theory into structure. His stunt at Queen Victoria’s naval review proved that science provides clarity, but engineering provides movement. It is the act of bridging math to metal that transforms knowledge into reality.

Mathematics as Prediction

Later, Hammack traces how mathematics evolved into a predictive engine through probability and statistics. From Pascal’s coin toss through Fisher’s extreme value theory to Herbert Thom’s hundred-year wind maps, math became a way to foresee disasters. Engineers use these models not as prophecy but as approximations. Statisticians may cringe at extrapolating beyond data, but engineers must act—bridges and skyscrapers must be built today, not after another century of observations. (Risk theorists note this as the pragmatic essence of applied math.)

Harmony Between Logic and Intuition

Science and math sharpen engineering’s rules of thumb—they turn blind intuition into guided creativity. Hammack’s metaphor is apt: physics provides the map, engineering drives the car. The two must coexist, but never be confused. To say engineering is applied science is like calling carpentry applied hammering. It isn’t the tool but the imagination that matters.

For Hammack, the lesson is personal and profound: use math and science to empower intuition, not replace it. They are guideposts in uncertainty, not the road itself.

When you flip a light switch, you’re touching a century-long web of collaboration. Hammack dismantles the myth of the lone inventor—whether Edison, Maxim, Latimer, or Coolidge—and reveals invention as a collective process shaped by manufacturing. What separates ideas from world-changing technology, he argues, isn’t genius; it’s the ability to mass-produce.

The Light Bulb Race

Edison gets credit, but Hiram Maxim built the first commercial bulbs and Lewis Latimer perfected carbon filament manufacturing. Their intertwined efforts show invention as accumulation, not isolation. Edison’s lab was industrial-scale trial and error; Maxim’s process refined uniform filaments chemically; Latimer solved fragility through clever mechanical envelopes. Each invention built atop another—nested heuristics modifying previous steps. “Inventors,” Hammack writes, “are nodes in a network, not singular sparks.”

Manufacturing as Innovation

Hammack declares that manufacturability determines success. William Coolidge’s ductile tungsten wire transformed fragile prototypes into mass-market bulbs. His process—heating, pressing, and hammering metal—embodied centuries-old metallurgical intuition linked back to Damascus sword forge methods. Like Wedgwood, Coolidge balanced empirical craft with science. This, Hammack claims, is where engineering truly shines: translating ideas into repeatable products.

Beyond the Myth

By comparing Edison’s incandescent lamp to Shuji Nakamura’s blue LED, Hammack shows invention as an evolutionary tree, not a lightning bolt. Each branch—filament, semiconductor, algorithm—represents cumulative knowledge. Myths of genius hide the reality of persistence and collaboration, discouraging future creators from seeing themselves as part of that continuum. Engineering tells a more democratic story: progress depends not on brilliance but on shared effort, tools, and adaptability.

If the light bulb is a symbol of invention, Hammack flips the metaphor: illumination doesn’t come from a single spark—it comes from a thousand glowing filaments refined together.

What happens when technology reshapes our lives faster than we can question it? Hammack ends his journey with the microwave oven—a fascinating parable of innovation and ethics. Born from radar magnetrons used in World War II, it became a domestic convenience and, inadvertently, a mirror of cultural bias. Through this story, Hammack brings the engineering method full circle, connecting creativity with moral responsibility.

From War to Kitchen

Engineer Percy Spencer’s reimagining of military radar as a cooking device began as pragmatic adaptation—using manufacturing heuristics to mass-produce magnetrons. Yet Raytheon’s redesign of the oven reflected postwar ideals: speed, efficiency, and the liberation of the American housewife. The irony Hammack exposes is that these appliances didn’t free women—they redefined domestic expectations, shifting responsibility rather than removing it. Technology, by solving one problem, often creates another.

The Myth of Linear Progress

Hammack critiques our tendency to see innovation as inevitable laddered progress—the “candy-bar moment” myth. True development, he argues, resembles a tangled tree or biological cladogram: multiple branches, dead ends, and cross-pollinations. Recognizing this complexity helps us avoid simplistic narratives of genius and instead appreciate engineering as an ongoing system, one that integrates social, ethical, and political forces.

Engineering as Ethical Practice

Technology isn't morally neutral; it manifests our choices. Hammack draws on thinkers like Hannah Arendt (who warned of technology’s dangers) and Lewis Mumford (who saw it as potential for moral renewal). He sides with pragmatic optimism: engineers, armed with awareness, can design for humanity’s good. He calls engineering “a creative profession that surpasses all others as the ultimate expression of human suppleness.” To practice engineering well is to practice ethics—because every design shapes how people live.

In closing, Hammack empowers you to see yourself as part of this continuum. Understanding the engineering method means seeing technology not as fate but as design—and realizing that we all share the responsibility to make that design humane.