[2] A ceteris paribus assumption is often key to scientific inquiry, because scientists seek to eliminate factors that perturb a relation of interest.
[3] Thus epidemiologists, for example, may seek to control independent variables as factors that may influence dependent variables—the outcomes of interest.
The earliest case of the Latin phrase being used in the English language publications was in the 17th century by William Petty, who used the clause to condition his labour theory of value.
Economist John Stuart Mill’s use of the Latin phrase had significant influences as he characterised economy through how it managed troubling factors.
[7] The importance that ceteris paribus has brought to economics is not only found in histographical interests, but is still vital to economists today, seen frequently in textbooks.
[5] One thing to note is that since economic variables can only be isolated in theory and not in practice, ceteris paribus can only ever highlight tendencies, not absolutes.
Alfred Marshall expressed the use of the clause as follows: The element of time is a chief cause of those difficulties in economic investigations which make it necessary for man with his limited powers to go step by step; breaking up a complex question, studying one bit at a time, and at last combining his partial solutions into a more or less complete solution of the whole riddle.
In breaking it up, he segregates those disturbing causes, whose wanderings happen to be inconvenient, for the time in a pound called Ceteris Paribus.
Temporal isolation requires the factors fixed under the ceteris paribus clause to actually move so slowly relative to the other influence that they can be taken as practically constant at any point in time.