Tuesday, May 12, 2009

Hume: Secrets, Agents, & Philosophers

A bit from David Hume's An Enquiry Concerning Human Understanding caught my eye:

Let the course of things be allowed hitherto ever so regular; that alone, without some new argument or inference, proves not that, for the future, it will continue so. In vain do you pretend to have learned the nature of bodies from your past experience. Their secret nature, and consequently all their effects and influence, may change, without any change in their sensible qualities. This happens sometimes, and with regard to some objects: Why may it not happen always, and with regard to all objects? What logic, what process or argument secures you against this supposition? My practice, you say, refutes my doubts. But you mistake the purport of my question. As an agent, I am quite satisfied in the point; but as a philosopher, who has some share of curiosity, I will not say scepticism, I want to learn the foundation of this inference. No reading, no enquiry has yet been able to remove my difficulty, or give me satisfaction in a matter of such importance. Can I do better than propose the difficulty to the public, even though, perhaps, I have small hopes of obtaining a solution? We shall at least, by this means, be sensible of our ignorance, if we do not augment our knowledge. [emphasis mine]
I hate to be daft, but concerning the bolded passage, what examples does Hume have in mind?

One way to read this is to emphasize "their secret nature" in the previous sentence -- it's easy to imagine instances where a poorly-understood object would generate differing, apparently random, hence unpredictable "effects and influences" over time. This is one way to define an object's "secret nature." The earliest astronomers noticed, for example, that while the vast majority of visible stars maintained a fixed position with respect to all the other stars, a small number of stars had a tendency to wander, and thus to defy easy projection. The Greeks called these planets, but since planet is just their word for wanderer, this doesn't achieve much besides bracket these exceptional stars as "stars that wander." It was only with centuries of refinements to technology and theory that it came to be recognized that these wanderers were not stars at all, but other objects in the same classification as the earth itself, and that their wanderings -- their "secret nature" -- could actually be explained by seeing them as orbiting the sun. Which is to say their "secret nature" was no longer secret after Copernicus, Brahe, Kepler, Galileo, and Newton had finished their work; they became and remain today as predictable in their "effects and influences" as anything else.

Objects with a "secret nature" as illustrated above do not get Hume off the hook, do they? It's tautological to say "stuff we don't understand isn't predictable" -- of course! That's why we consider it unpredictable! But much of nature isn't that way at all.

It seems to me that for his claim to have any force, it needs examples of objects without "secret natures" that still vary in their "effects and influences." Are there any? If there are -- if there are things we understand well by dint of rigorous analysis, theory, and observation but whose effects we nevertheless cannot reliably predict -- then Hume's doubts as a philosopher might be vindicated: we must suspend our confidence that even the longest-established patterns of cause-and-effect will hold true in the future.

For me, I take the part of the agent. I am skeptical of Hume's skepticism.


Anonymous said...

Whenever I couldn't get my college chemistry lab results to match the expected results, I took comfort in the fact that maybe the laws of nature were working differently that day. Unfortunately the teaching assistant who graded my work wasn't much of a Hume fan however.

The Barefoot Bum said...

Hume is arguing correctly against the idea that we can take a naive, trivial or superficial version of the premise, "The future always resembles the past," as deductively valid. His critique is not against the scientific method, but a prescient rebuttal of naive empiricism or positivism.

Hume writes at the very beginning of the scientific revolution, a revolution that consists not only of holding evidence as authoritative, but also a revolutionary new way of thinking about the evidence, abandoning millennia of philosophy that considered deductivist, syllogistic reasoning to be the sine qua non of rationality.