Ceteris paribus
from 1600 Scholastic in origin; central to economics from Marshall
Hold everything else still, vary one thing, and state a relation that is true only under a condition that never actually obtains.
- Active
- from 1600
- Where
- Europe, later Cambridge
- Also
- ceteris paribus
- Status
- In use
- Tradition
- Devices and constraints
What it is
A ceteris paribus clause restricts a claim to conditions in which everything not mentioned is held constant. Raising the price reduces demand — other things being equal. The clause is what makes the claim true, and it is also what makes it hard to test, since other things are never equal.
As a device it is applied to somebody else's claim: find the clause, stated or implied, and ask what it is holding still.
How it works
Take the claim. Identify the ceteris paribus clause, which is often unstated. List what it is holding constant. Ask whether those things were in fact constant in the case at hand. Where they were not, the claim has not been shown to fail — it has not been tested.
That last distinction is the useful one and the one most often missed in argument.
How it is applied
- The claim relates one variable to another
- It holds only if the unmentioned variables are constant
- List what is being held constant
- Ask whether those were constant in the case at hand
- If not, the case neither confirms nor refutes the claim
The device applied
Proposition The pricing change was not shown to have failed.
- The claim behind the change: raising the gate fee at the tip reduces the volume of clean fill received, other things being equal.
- The fee rose by forty per cent in July 2024. Volume rose by twelve per cent over the following year, and the report concludes the pricing lever does not work here.
- What the clause is holding constant: the fees at competing facilities, the volume of construction in the catchment, and the enforcement of illegal dumping.
- In fact all three moved. The nearest private facility closed in September 2024, two subdivisions began earthworks in the same year, and dumping enforcement was suspended when the ranger position was vacant.
- So the year in question does not test the claim. It tests the claim plus three uncontrolled variables, at least two of which push volume the other way and are individually larger than the effect being looked for.
Therefore The pricing change has not been shown to have failed; it has not been evaluated, and any evaluation needs a comparison that holds the competing facility and the construction volume still.
The device did not defend the pricing change. It identified that the evidence offered against it is not evidence about it, which is a different and more useful finding than either party had.
What it is good for
Reading evaluations, before-and-after comparisons and any claim that a measure did or did not work. It is the fastest way to see whether a result is about the thing it claims to be about.
Where it fails
The clause can be made to absorb every failure. If any disconfirming case can be explained by something else not having been equal, the claim is protected from all evidence and has stopped saying anything. Economics has been arguing about this since Mill, and Earman and Roberts pressed the general version: a law with an open-ended ceteris paribus clause may not be testable even in principle.
The list is also open. Nobody can enumerate everything being held constant, so the clause is always incomplete, and the difference between a legitimate restriction and an escape hatch is a matter of judgement.
Common misconceptions
That it is a hedge or a weakening. It is a specification of the claim's domain, and a claim without one is usually not stronger but false.
Where it came from
Scholastic Latin, and standard in the reasoning of the seventeenth-century natural philosophers. Marshall makes it methodologically central to economics in 1890.
What became of it
Indispensable in economics and the special sciences, and the subject of a long unresolved argument in philosophy of science about whether laws containing it can be laws at all.
Lasting influence
It is how every special science states a regularity, since none of them has exceptionless laws.
Why it still matters
Constant, and directly useful in reading any evaluation.
Put another way
A photograph taken with everything else nailed down, in a room where nothing is.
Texts
John Earman and John Roberts, Ceteris Paribus, There Is No Problem of Provisos
The sharpest statement of why such clauses may make a law untestable, and the argument the defenders have to answer.
Where to start
Take any before-and-after evaluation and list what would have had to stay still. It rarely did.
The surprising bit
The clause that makes a claim precise is the same clause that can make it untestable, and there is no agreed way to tell which it is doing.
In their own words
The element of time is the chief cause of those difficulties which make it necessary for man with his limited powers to go step by step
Who held it
John Earman
Connections
- Parallel to
- Eidetic variation
The verdict
Necessary for stating anything true about a complicated world, and the most respectable way there is to avoid being wrong.