What Is Value? Labor Theory vs Marginal Utility

Two competing theories of why things have economic value: the labor put into them, or their usefulness at the margin.

Why is a diamond expensive while water, essential for survival, is usually cheap? This question, sometimes called the diamond-water paradox, sits at the center of one of economics’ oldest and most consequential debates: what actually determines the value of a good?

The labor theory of value

The labor theory of value holds that the economic value of a good is determined primarily by the amount of labor required to produce it. This idea appears in early classical economics, including in the writings of Adam Smith and David Ricardo, and was later developed further and given a more central role by Karl Marx, both discussed elsewhere in this module. Under this view, a good that takes many hours of skilled labor to produce should generally be worth more than a good that can be produced quickly and easily, because the labor embedded within it represents a real cost to society that must be reflected in its value.

The marginal utility revolution

Beginning in the late nineteenth century, a group of economists working somewhat independently - including William Stanley Jevons, Carl Menger, and Léon Walras - developed an alternative explanation now called marginal utility, the additional satisfaction or usefulness a person gains from consuming one more unit of a good, given how much of that good they already have. This theory holds that value comes not from how much labor went into producing a good, but from how much additional value a consumer places on having one more unit of it, in their own specific circumstances.

Solving the diamond-water paradox

Why diamonds cost more than water

Water is essential to life, so its total value to humanity is enormous - yet in most places it is abundant and cheap. Diamonds are not essential to survival at all, yet they are expensive. Marginal utility resolves this puzzle by distinguishing total value from value at the margin: because water is typically abundant, the value of one additional glass of water to someone who already has plentiful access is fairly low, even though water overall is essential. Diamonds are scarce, so the value of one additional diamond remains high even though diamonds as a category matter far less to survival than water does. Price tracks this marginal value, not the total importance of the entire category of good.

Subjective value

Marginal utility theory rests on the idea of subjective value - the notion that a good’s value is not an inherent, objective property of the good itself, but depends on how much a particular individual, in their particular circumstances, values having more of it. This was a significant philosophical shift: rather than searching for some objective source of value baked into a good, like the labor used to produce it, economists working in this tradition argued that value is ultimately something individuals assign based on their own preferences and circumstances, and prices in a market emerge from the interaction of many such subjective valuations.

Assuming one theory is simply "correct" and the other "wrong"

It's tempting to treat this as a settled dispute with one clear winner, but that oversimplifies a genuinely complex history. Marginal utility theory became dominant in mainstream economics because it more successfully explains price formation and consumer behavior in specific markets, including puzzles like the diamond-water paradox that the labor theory struggled with. However, the labor theory of value was never solely about predicting market prices; for Marx in particular, it was also a tool for analyzing exploitation and the relationship between workers and capital, a different kind of question than simply explaining why prices are what they are. The two theories were partly answering different questions, not only competing to answer the same one.

Why this debate still matters

This question of what gives things value is not merely historical trivia; it touches deep philosophical assumptions still embedded in economic thinking today. Marginal utility theory, now foundational to mainstream microeconomics, assumes that value is fundamentally personal and relative to circumstance, which has significant implications for how economists think about topics ranging from pricing to inequality. The labor theory’s legacy, meanwhile, persists in ongoing debates about whether market prices fully capture everything that matters about how goods are produced, including the human labor and conditions behind them.

Key takeaways

The labor theory of value holds that a good's value comes from the labor required to produce it.
Marginal utility theory holds that value comes from the additional satisfaction gained from one more unit of a good.
Marginal utility explains the diamond-water paradox: value depends on scarcity at the margin, not total importance.
Marginal utility theory rests on the idea that value is subjective, depending on individual circumstances.
Marginal utility became dominant in mainstream economics for explaining prices and consumer behavior.
The labor theory's legacy persists in debates about whether prices fully capture the human cost of production.