I repeatedly find attacks on positions in the social sciences made based on extremely limited and, frankly, antiquated views of how the physical sciences proceed. I will give one example from a rightist criticism of a leftist view, and one that is a leftist criticism of a rightist view, to illustrate that my point has nothing to do with ideology — or perhaps, that it has to do with the way ideology can lead one to embrace flimsy criticisms of other’s positions.
“In chapter 15, we saw how Keynes wrote N = F(D), which means that employment, denoted N, is a function of demand. Demand however is defined as expected sales, not actual sales. We noted that expectations are not a measurable quantity and thus do not belong in an equation.”
Well, one way to measure these expectations would be to walk around and ask the entrepreneurs “How much do you expect to sell this year?” then total up those amounts. Why in the world this would not be a fine measurable quantity is unclear.
But perhaps even worse is Lewis’s contention that only a “measurable quantity” belongs in a mathematical equation. So, let us strike pi from all of our equations, and e, and, most certainly, i! All complex numbers must be banished, and negative numbers are fairly suspect as well.
Furthermore, most of the entities dealt with by modern physics are not directly measurable. Instead, what we measure is a dial reading or a trail on a photographic plate, things which require a great deal of theory to connect them to entities like electrical fields or positrons. As the philosopher Susanne Langer wrote:
The sense-data on which the propositions of modern science rest are, for the most part, little photographic spots and blurs, or inky curved lines on paper. These data are empirical enough, but of course they are not themselves the phenomena in question; the actual phenomena stand behind them as their supposed causes… we see only the fluctuations of a tiny arrow, the trailing path of a stylus, or the appearance of a speck of light, and calculate to the “facts” of our science. What is directly observable is only a sign of the “physical fact”; it requires interpretation to yield scientific propositions… and [realizing this,] all at once, the edifice of human knowledge stands before us, not as a vast collection of sense reports, but as a structure of facts that are symbols and laws that are their meanings.
(Philosophy in a New Key)
And surely this was what Keynes thought: aggregate demand may not be directly observable, but we can formulate laws by which its effects are observable, for instance, in a recession. Now, whether he was correct or not is not my topic, but there is certainly nothing unscientific about his hypothesis.
“However, [marginalism's] Achilles’ heel was the very notion of ‘marginal utility’. Marginal utility, let us be frank, is hardly a scientific concept: unobservable, unmeasurable and untestable, marginal utility is a notion with very dubious scientific standing.”
Unobservable, unmeasurable and untestable — like, say, infinitesimals in calculus! (And people like Berkeley directed just such criticism at infinitesimals and other mathematical notions.) Once again, we have some unfounded belief that scientific entities must be directly observable, rather than observed by their hypothesized effects. (And certainly the theory of marginal utility predicts many observable phenomena, such as the lack of a price for air in normal circumstances.)
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