THE “WHAT COULD FALSIFY IT?” OBJECTION
3 THE “WHAT COULD FALSIFY IT?” OBJECTION
The more modest one’s imagination, the more impressive this objection is likely to seem, which should put one on guard immediately. There is more than a whiff of an argumentum ad ignorantiam about this objection (“I cannot imagine how FP could be falsified; therefore, it isn’t a falsifiable theory”). Let me try to sustain this diagnosis by meeting the objection head on, by trying to repair the very ignorance that makes it plausible.
The objector’s question is rhetorical, of course, and gets its force by placing an unreasonable demand on one’s imagination. With theories of the complexity and broad scope of FP, it is in general difficult or impossible to cite any single experiment or observation that would refute the theory at one blow. If we have learned anything from Duhem, Quine, Lakatos, and Kuhn, it is that theories, especially theories of broad scope and complexity, tend to die of slow empirical strangulation rather than by quick observational guillotine. This is triply true if the theory is also vague, incomplete, and festooned with ceteris paribus clauses, as FP most famously is.
Even so, theories can have severe empirical pressure put on them, by chronic poor performance in a proprietary domain (cf. Ptolemaic astronomy); by incompatibility with closely neighboring theories that are performing extremely well (cf. Vitalism vis- à-vis metabolic chemistry and molecular biology); by poor extension to domains continuous with but outside the domain of initial performance (cf. Newtonian mechanics in strong gravitational fields or high relative velocities); and finally, by the occasional empirical result carefully contrived to discriminate in some important way between competing alternatives (cf. Eddington’s eclipse expedition, or the comparative statistical trials of Freudian vs other forms of psychotherapy). All but the last mode of pressure require significant periods of time for the empirical pressure to accumulate, and tests of the last kind are relatively rare, often hard to think of, usually difficult to set up, and regularly ambiguous in their outcomes even so.
Can we imagine pressures of these four prototypical kinds building up on FP? Not only can we, but the relevant pressures are already there. Some of us think we can hear the edifice creaking even as we discuss the matter. FP’s explanatory success in predicting and explaining belief acquisition, practical deliberation, emotional reaction, and physical behavior is far from zero, to be sure, but it is even farther from the possible limit of 100 percent success in the capacity to predict and explain all such activities. “The complexity of human cognition allows no more than a rough grasp of even its major activities,” it is said in
180 POSTSCRIPT And FP’s marginal performance in its proprietary domains is now at least twenty
centuries in evidence. This is chronically poor performance by any measure. FP is also under pressure from computational neuroscience, whose portrayal of the fundamental kinematics and dynamics of human and animal cognition is profoundly different from the propositional-attitude psychology of FP. The brain’s computational activity is no longer the smooth-walled mystery it used to
be. We are now contemplating the high-dimensional vector of neuronal activation-levels as the fundamental mode of representation in the brain. And we are now contemplating the vector-to-vector transformation, via vast matrices of synaptic connections, as the fundamental mode of computation in the brain (more on this below). Propositions and inferences are there in the brain only in some profoundly hidden and undiscovered form, or only in some small and uniquely human subsystem, if they are there at all.
We cannot yet insist that no accommodation will be found. Nor can we insist that computational neuroscience (CN) has things right. But CN is a robustly progressive and expansionist research program. And undeniably there is a prima facie failure-of-fit between the relevant ontologies and their correlative dynamics. Here is a second dimension of empirical pressure on FP. This, incidentally, is the substance of the worry, cited earlier, that FP will fail to find a smooth reduction within a more penetrating successor or substrate theory.
FP is subject to a third dimension of empirical pressure in its failure to extend successfully to adjacent domains. FP functions best for normal, adult, language- using humans in mundane situations. Its explanatory and predictive performance for prelinguistic children and animals is decidedly poorer. And its performance for brain-damaged, demented, drugged, depressed, manic, schizophrenic, or profoundly stressed humans is pathetic. Many attempts have been made to extend FP into these domains. Freud’s attempt is perhaps the most famous. They have all been conspicuous failures.
The fourth dimension of empirical pressure is the hardest to address, for the reasons outlined earlier. I shall stick my neck out even so, if only to illustrate some relevant possibilities. One way to perform an empirical test of the hypothesis that the cognition of humans and the higher animals is an inference- rule-governed dance of prepositional attitudes is to construct an artifactual system that deliberately and unquestionably does conduct its “cognitive” affairs in exactly that way. The purpose is to see if such a system can then display, in real time, all of the cognitive capacities that humans and the higher animals display.
A positive result would be highly encouraging for the hypothesis, though not decisive, because of the possibility that there is more than one way to achieve such cognitive capacities, and the possibility that the human and the artifact achieve them differently. On the other hand, persistently negative results in this experiment would augur very darkly for the hypothesis under test. If the relevant cognitive capacities never emerge from such a system, no matter how we tinker
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factor of roughly 10 6 with electronic machines over biological brains), then we have a gathering case that such a system is not in fact a reconstruction of our own computational strategy, a gathering case that our own system, and that of animals, must be using some quite different strategy.
The reader will perceive that I cite this example not just because it is a possible empirical test of the hypothesis at issue, but also because the AI community has in effect been performing and re-performing this test for something close to a quarter century now. The results have been persistently negative in just the way feared. The results are indecisive, to be sure. But there is widespread acknowledgment of and celebrated disappointment in the decreasing cognitive returns generated in the classical fashion from machines of ever- increasing speed and power. This is empirical evidence relevant to the hypothesis cited above, and it certainly isn’t positive.
All told then, it is indeed possible for FP to suffer disconfirmatory empirical pressure. It does so in four different dimensions, and the pressure is the more powerful for being negative in all four. It is at least arguable that FP is approaching the brink of falsification already.