Mustang19, I think you should read this article that was recently recommended to me. It’s a bit long, I know, but here’s the enlightening passages.
Experience is necessarily of past events. It can be resorted to for the prediction of future events only with the aid of the assumption that an invariable uniformity prevails in the concatenation and succession of natural phenomena.
[…]
The “category of causality” is our inbuilt conception that past regularity predicts future regularity. That conception is a prerequisite to all reasoning regarding cause and effect in the natural world. As Mises wrote, agreeing with Hume, there is no deductive proof that past regularity predicts future regularity.
[…]
First let us reflect on the methodology of geometry. In preclassical times, geometry was largely empirical. For example, ancient Egyptian surveyors called “rope stretchers” used to find right angles by stretching out knotted ropes to make a 3-4-5 triangle (a triangle with sides in the ratio of 3 to 4 to 5). The geometric principle that all 3-4-5 triangles form right angles might have been discovered by the Egyptians through experience, by simply noticing that such triangles generally have perpendicular legs by eyeballing multiple instances of them.
However, the ancient Greeks pioneered using long chains of deductive inferences to discover geometric principles (fortunately, there was no ancient Greek Congressman Clay at the time to deride this deductive scientific enterprise). And so the Greeks could discover the same principle (that all 3-4-5 triangles form right angles) by reasoning from the Pythagorean theorem. And the Greeks were able to use deductive geometry to discover a great many geometric principles that would have been too subtle to find with empirical methods.[32]
Nowadays the deductive method for geometry is universally embraced. A good geometry teacher will not demonstrate the Pythagorean theorem with measuring tape and a pile of plastic right triangles, except perhaps as a preliminary exercise. She will teach her students to derive the theorem from prior premises.
What if, when measuring plastic triangles, one of the geometry teacher’s students discovers something that does not seem to fit the Pythagorean theorem as it was taught to him by the teacher? There are a few possible explanations for such an occurrence.
Perhaps the teacher, bizarrely, doesn’t know the correct Pythagorean theorem herself, or how to derive it. An economic analogy to this situation is when a theoretical economist introduces vicious formulations (as the classical economists did with their value theory) and invalid reasoning (as Keynes did with much of his work) to build a false economic theorem.
Perhaps the student measured the right triangles incorrectly. This would be analogous to an economic statistician gathering faulty data.
Perhaps the student is not even dealing with right triangles in the first place, and so the Pythagorean theorem is not applicable. This would be analogous to an economist trying to explain a rise in a good’s price using the quantity theory of money when the quantity of money didn’t actually change, and instead the price rose because of an increase in demand.
If economic data do not seem to demonstrate the playing out of a certain market process described by economic theory (assuming the theory is sound and the data are correct), that would indicate that circumstances must have been dominated by another market process (also described by pure economic theory), another set of factors, or the interplay of several market processes/sets of factors.
The economic historian uses data to determine which economic laws are most relevant in any given episode. If, for example, the economic historian discovers trustworthy data that show that after an increase in the supply of a certain good the price for that good increased, instead of falling, that would not testify against the law of supply. That would instead be an indication that other relevant factors are at work, like perhaps a precipitous drop in the supply of another good for which the first good can serve as a substitute.
Whatever the case ultimately proves to be, what should the geometry student do when faced with data that do not harmonize with the theory he is using? Should he proudly announce that he has refuted the “orthodoxy of Pythagoras” and publish a new theorem, based on his measurements? Should he gather a larger sample set of plastic triangles and perform statistical analysis on the data gathered?
Of course not. He should check the soundness of the reasoning used in deriving the theorem, check his measurements, and check the applicability of the theorem to the data.
Insofar as the student derived the Pythagorean theorem using discursive reasoning, he was a geometer. But insofar as he was using geometry along with measurement to study plastic triangles, he was a topographer, not a geometer. While geometry is indispensable for topography, it is completely invalid to try to derive geometric laws from topography.
This is analogous to the crucial distinction between economics and economic history. Insofar as a scholar derives economic theorems using discursive reasoning, he is an economist. But insofar as he uses economics along with data-gathering to study actual events, he is an economic historian, not an economist. While economics is indispensable for economic history, it is completely invalid to try to derive economic laws from history.