Theory first, then description

Picking up on a unfollowed line of reasoning from my last post, I’d like to argue what might seem like a bold claim: The only practical way to make any discoveries or advances in any science, including syntax, is by starting with the theory.

First let me head off a possible objection, namely the Kuhnian objection that sciences don’t advance, they simply move from paradigm to paradigm. If this were true, then there is a version of my claim which is still defensible: If discoveries or advances are possible in syntax or any science, then they are possible only by starting with the theory. So, if the Kuhnian is right, then my claim is might be strictly academic, but it’s not necessarily wrong. Of course, if the Kuhnian objection is correct, then the fact that you are reading this now is tantamount to a literal miracle.

Since I take discoveries and advance to be two separate things, I’ll take them one at a time, starting with the latter.

A science advances, in my estimation, when one of two things happen: either an additional general truth is derived, or two general truths are subsumed under a single general truth. Theoretical sciences traffic in general statements, and they do so using deductive reasoning. Since deduction generates true statements from true statements, then it stands to reason that theoretical sciences are capable, in principle, of advancing. Descriptive sciences, on the other hand, traffic in particular truths (i.e., facts) and does so by a combination of observation and induction. Since observation only yields facts and induction cannot reliably derive general truths from facts, descriptive sciences cannot advance.

Turning to discoveries, which I take to be the addition of novel existential truths to our knowledge. Since existential statements (i.e., “There are X” or “X exists”) are derivable from particular statements, they can in principle be derived in a descriptive science. Hence, my use of the qualifier “practical” in my claim. My claim regarding discovery, then, is that descriptive scientific work can reliably make discoveries only insofar as it is guided by theoretical scientific work. To argue for my claim, I will first employ a thought experiment:

A densely freckled patient wishes to know whether they have any signs melanoma. They first visit a lab tech who is trained in taking biopsies but whose knowledge of melanoma is purely instrumental. He can take a biopsy, run a test on it, and interpret the results of that test. His diagnostic plan is to biopsy every single freckle on the patient’s body.

The patient’s second visit is to a trained dermatologist, whose understanding of the general nature of melanoma, allows her to recognize likely tumors by sight alone. Her diagnostic plan is to carefully examine the patient’s skin and order biopsies on the likely tumors.

Which diagnostic plan would you choose if you were this patient?

Clearly the dermatologist’s plan is more practical, and it is only possible because of her theoretical understanding of melanoma. Of course, both methods would have a good shot at discovering a tumor if it existed, assuming the lab tech is exceptionally thorough and the dermatologist is exceptionally knowlegable about melanoma. However, suppose we increased the amount of patients that wished to be screened. Clearly the rate of discovery of tumors would go down in either case, but likely the decline would be greater for the lab tech, whose initial burden of work is greater. Or suppose we vary the degree of thoroughness of the lab tech and the degree of tumor-knowledge of the dermatologist. An increase in thoroughness, would likely slow down the lab tech, while an increase of tumor-knowledge would speed up the dermatologist. In both cases, theoretical knowledge trumps descriptive skill because theoretical knowledge allows us to distinguish relevant data from irrelevant data.

The second part of my argument comes from the history of science, specifically the discovery of the planet Neptune. The story, at least according to Wikipedia, goes as follows: multiple astronomers noticed the the orbit of Uranus (Neptune’s neighbour closer to the sun) did not line up with what Newton’s theory of gravitation predicted. This led them to hypothesize a yet to be discovered planet whose gravitational pull disturbed the orbit of Uranus. And beyond just hypothesizing it’s existence, they, and in particular Urbain Le Verrier, were able to calculate its position in the sky at a particular time, and an astronomer with access to a suitable observatory, following Le Verrier’s instructions was able to observe Neptune in 1846.

This on its own is a powerful demonstration of the usefulness of theoretical science, but it’s made more powerful when you take into account the fact that Galileo observed Neptune as early as 1613, but he did not discover it. While this may seem like a contradiction, it makes more sense when you add that Galileo failed to recognize that Neptune was a planet, mistaking it for a star, because he had no reason to think he would find a planet there.

To sum up, descriptive science is incapable of making advances, because it traffics in particulars. And while it is indeed capable of making discoveries it is horribly inefficient. Theoretical science, on the other hand, is perfectly suited to advances, and can guide descriptive science to discoveries like a rider guides a horse.This leads to an inversion the prevailing wisdom that says only once we have a broad description of the relevant phenomena are we in a position to build a theory. On the contrary! Only once we have a clear theory are we even able to know what the relevant phenomena are.