Naturalized epistemology

2. Internalism versus externalism

Like Hume, contemporary naturalists are empiricists. For example, in ‘Epistemology Naturalized’ Quine explicitly affirms a version of Humean empiricism:

It was sad for epistemologists, Hume and others, to have to acquiesce in the impossibility of strictly deriving the science of the external world from sensory evidence. Two cardinal tenets of empiricism remained unassailable, however, and so remain to this day. One is that whatever evidence there is for science is sensory evidence. The other…is that all inculcation of meanings of words must rest ultimately on sensory evidence.

(Quine 1969: 75)

But contemporary naturalists do not have in mind the introspective sort of empiricism advocated by Hume but, rather, intersubjective empiricism. Instead of simply taking our mental faculties and the data of introspection for granted and accounting for knowledge from that perspective, Quine and other naturalists suggest that we take a more full-bodied version of scientific practice for granted, and account for knowledge from that perspective. The empiricist science on which naturalists rely is conducted in the public domain. Scientists use microscopes and other instruments to extend their senses, and the observations upon which they rely are not data of introspection but rather observations that are at least in principle publicly confirmable (see Empiricism; Introspection).

Naturalists think that the stimulation of sensory receptors helps to determine whether or not people know the truth of beliefs that are causally linked to those stimulations. Yet the stimulations themselves are usually not noticed by the people in whom they occur. Naturalists are externalists, defined by Laurence BonJour (1985), following D.M. Armstrong (1973), as theorists according to whom facts that are external to an agent’s conception of the situation can serve to justify that agent’s beliefs in a way that is sufficient for knowledge (see Internalism and externalism in epistemology). Internalists, by contrast, would insist that all knowledge is based on justifications that are in some sense in the cognitive possession of the knower. A related view is that epistemology, or knowledge about knowledge, is based on such justifications. Consider the following arguments for these internalist positions.

First, as BonJour emphasizes, justifications that are in no way possessed by an agent are completely arbitrary (unsupported), at least so far as the agent can tell from the agent’s own point of view, and accepting arbitrary beliefs is a bad idea from the standpoint of getting to the truth, which is the goal of the epistemic agent. Yet externalists claim that it is possible for agents to acquire knowledge through sources about which those agents believe little or nothing. Their sources might be a causal chain, a reliable belief-formation process, an information channel, or all three (see Knowledge, causal theory of; Information theory and epistemology; Reliabilism). Internalists disagree, since it is epistemically irresponsible to believe something through some avenue without checking out the truth-conductivity credentials of that avenue.

The main problem with this first line of thought is that the internalists’ assumptions seem to lead immediately to sceptical results. For internalists want an avenue to the truth but they want to accept nothing except what is justifiable, and nothing as justification except what is available to them ‘from the inside’. That means they need an avenue to the truth that can be defended as such on the basis of what is available ‘from the inside’, a task that appears to be impossible. No empirical premise will serve in the defence since empirical premises will either be accepted without justification (arbitrarily) or justified on the basis of some other empirical premise, thus initiating a regress.

A second line of argument gives up on the attempt to show that all knowledge conforms to internalist assumptions, but purports to show that epistemology fits the internalist view: since logic is a priori accessible if any body of knowledge is, the thought that there is an inductive as well as a deductive logic may lead theorists to suggest that knowledge is the product of reasoning that conforms to valid deductive and inductive forms of argument. Some of the assumptions that are fed into the arguments might not conform to internalist assumptions, but the reasoning does. So we can understand epistemology to be an a priori study of the argument forms to which reasoning ought ideally to conform.

One problem here is that, unlike deductive logic, inductive logic is not the study of argument forms. Ultimately inductive logicians invoke appeals to the way the world is, appeals which internalists want to avoid. Except in trivial cases, that one statement makes another probable is a claim about the world, not about the forms of those statements. More seriously, in the phrase ‘reasoning that conforms to valid argument forms’ there is a conflation of argument with reasoning. As Gilbert Harman (1986) and others have emphasized, these are quite distinct things. The study of arguments and argument forms is logic; the study of reasoned belief revision is the study of the belief-management practices governing those revisions. Principles of belief management would tell us when epistemic agents should retain their beliefs and when and how they should revise them. The inference rules of logic do not tell us when revision is appropriate. Inference rules can tell us many things; for example, suppose that we believe the premises of an argument – inference rules can tell us that the premises of that argument entail its conclusion. But that is not the same thing as a recommendation that (say) we affirm the conclusion. In fact, belief-management principles might tell us that we ought to drop one of the premises rather than accept the conclusion.

Once we distinguish between logic and belief management, like Harman we may become quite sceptical about the existence of anything like an inductive logic. An inductive logic would be a logic that resembles deductive logic except that the conclusions of ‘valid’ inductive arguments are merely made probable by their premises, not entailed by them. That such a logic exists is not entailed by the existence of inductive reasoning, and the fact that so little progress has been made towards developing an inductive logic might lead us to suspect that there is no such subject to be investigated (see Inductive inference). Moreover, if inductive logic does not exist, good inductive reasoning cannot be simply reasoning that conforms to inductive logic. (Some have held that probability theory provides the basis of inductive logic – see Probability theory and epistemology.)

So the epistemic activity of inductive reasoning might not be illuminated by advances in ‘inductive logic’. A related point is that much epistemic activity probably does not involve beliefs or any other proposition-related states at all. As Paul Churchland (1979: 128) has argued, a great deal of information is processed by infants, and their prelinguistic behaviour does not invite ascriptions of propositional attitudes to them. ‘Rational… intellectual development in an infant cannot be…usefully represented by a sequence of sets of sentences suitably related’. Information processing in infants, as well as the processing by virtue of which sensory stimulations are assimilated by adult brains prior to the formation of beliefs, would presumably be articulated by principles of which epistemic agents themselves are entirely unaware and to which they could not purposely conform even if they wanted to. Churchland takes such facts to suggest that any account of knowledge in terms of ‘sentences suitably related’ is bound to be superficial; a proper theory would deal in more primitive parameters that apply to pre-linguistic processing, and would account for the way epistemic agents deal with beliefs as a derivative case.

In sum, critics of naturalized epistemology who say that knowledge or epistemology is based on justifications in the cognitive possession of knowers face some severe difficulties.