Why economics is not allowed ceteris paribus laws

Economics differs from physics, we are told, in that the laws economics studies hold only ceteris paribus whereas those of physics are supposed to obtain universally and without condition. Does this point to a metaphysical difference between the laws the two disciplines study or does it reflect merely a deficiency in the level of accomplishment of economics as compared to physics?

The conventional regularity account of laws tells us it must be the latter. On this account a theoretical law is a statement of some kind of regular association, usually supposed to hold “by necessity.” The idea of necessity is notoriously problematic. Within the kind of empiricist philosophy that motivates the regularity account it is difficult to explain what constitutes the difference between law-like regularities and those that hold only by accident, “nonsense” correlations that cannot be relied on. I shall not be concerned with necessity here; I want to focus on the associations themselves. These can be either universal, in which case the law is deterministic, or they may be merely probabilistic. The regularity account is grounded in a version of empiricism that traces back to the philosophy of David Hume. Empiricism puts severe restrictions on the kinds of properties that appear in Nature's laws, or at least on the kinds of properties that can be referred to in the law-statements we write down in our theories. These must be observable or measurable. It also restricts the kinds of facts we can learn: the only claims about these quantities that are admissible into the domain of science are facts about patterns of their co-occurrence.