Economic Methodology

A positive statement is a statement of fact that can be tested against evidence and shown to be true or false. It is objective. For example, 'a rise in the price of petrol reduces the quantity of petrol demanded' is positive because it predicts a relationship that data can confirm or refute. Importantly, a positive statement need not actually be true — it only needs to be testable.

A normative statement is a value judgement about what ought or should be. It cannot be proved true or false because it depends on opinions and priorities. For example, 'the government should reduce taxes on the poor' is normative — it reflects a view about fairness rather than a testable fact. Normative statements often contain words such as 'should', 'ought', 'fair' or 'too high'.

The distinction matters for several reasons. First, it allows economists to use evidence to settle positive questions objectively, giving policy debate a factual foundation. Second, it ensures that opinions are not disguised as facts — separating the effects of a policy (positive) from whether it is desirable (normative) keeps analysis honest. Third, it explains why economists who agree on the facts can still disagree on policy: they hold different value judgements. Recognising which parts of an argument are positive and which are normative is therefore essential to clear economic reasoning.

Ceteris paribus means 'other things being equal' — all other relevant variables are assumed to stay constant. Economists use it to isolate the effect of a single variable. For example, the law of demand states that, ceteris paribus, a rise in price reduces quantity demanded; by holding income, tastes and the prices of other goods constant, economists can study the pure relationship between price and quantity. This makes a complex world manageable and allows clear cause-and-effect reasoning, such as distinguishing a movement along a demand curve (price changes only) from a shift (a non-price factor changes).

Its limitation is that, in the real world, other things rarely are equal — many variables change at the same time. A price change might coincide with a rise in incomes or a change in tastes, so the observed change in quantity may not match the ceteris paribus prediction. Conclusions drawn under the assumption must therefore be applied to messy reality with caution, recognising that several forces usually act together.

The source shows that what a producer can do depends on the time period.

In the short run, at least one factor of production is fixed: the coffee producer's existing trees are fixed, so 'this season' output cannot be raised regardless of demand — only variable factors such as labour can change, and these cannot create new trees in time.

In the long run, all factors become variable: the plan to 'plant more trees' increases the previously fixed capital (the orchard), allowing greater output once the new trees mature.

In the very long run, technology itself can change: adopting 'drought-resistant varieties' is a change in the state of technical knowledge, which can raise productivity and output beyond what the original methods allowed.

The example therefore shows that supply responses are limited in the short run but expand in the long run and very long run as more factors — and finally technology — can be varied.

Economics shares much with the natural sciences. Economists follow a scientific method: they build models (such as demand and supply), form hypotheses ('a rise in price reduces quantity demanded'), and test them against real-world data. Many relationships are quantified and used to make predictions, just as in physics or chemistry. The use of ceteris paribus mirrors the scientist's attempt to isolate variables, and positive economics deals in testable, objective claims. On these grounds economics has a strong claim to be a science.

However, there are important differences. Economics studies human behaviour, which is variable and influenced by expectations, emotions and changing institutions, making it far less predictable than physical matter. Economists usually cannot run controlled experiments on an entire economy, so they rely on imperfect historical data in which ceteris paribus rarely holds — making cause and effect hard to establish. As a result, economists frequently disagree even when looking at the same evidence. Furthermore, much of economics is concerned with policy, where normative value judgements are unavoidable; deciding whether a policy is 'good' is not a scientific question at all.

Judgement. Economics is best described as a social science: it uses scientific methods but applies them to an unpredictable human subject that resists controlled experimentation. Its positive branch is genuinely scientific — claims are testable in principle — while its normative branch is not. The most defensible conclusion is therefore that economics is a science in its method and in its positive analysis, but the involvement of human behaviour and value judgements means it can never be as exact or conclusive as the natural sciences.