Regimenting Common Sense Concepts of Knowledge and Justification after Gettier

One of forms common sense can take is that of clusters of strong and widely shared intuitions about some idea or subject. Something philosophy has typically done, since Plato onwards, is probing those clusters of intuitions in order to see if they can be subsumed under a coherent concept or definition, or not. If they can, philosophy wonders if this concept or definition is useful, well grounded or otherwise acceptable, and if not how it might be amended. If intuitions cannot be subsumed under a coherent concept, philosophy searches how this could possibly be done by rejecting the smallest number of weaker or more peripheral intuitions. Thus philosophy analyses, evaluates, regiments and possibly reforms common sense. This is what the debates rehearsed in the following pages do with the common sense notions of knowledge and justification, where the examples and counterexamples used by Plato, Gettier and subsequent literature are just ways to bring out the relevant intuitions. Gettier thought that the counterexamples offered in his famous “Is Justified True Belief Knowledge?” (1963) questioned the tripartite definition of knowledge as true justified belief in Plato’s Theaetetus; but I argue that they can as well be seen as a challenge to reassess the nature of justification, a question Plato had left open in the conclusion of that dialogue. He was very clear that knowledge must be non-accidental, and justification is required precisely to warrant the non-accidental character of beliefs. Gettier’s counterexamples and others similar in the subsequent literature show that justification cannot fully accomplish that task unless it makes the justified beliefs in principle certain. But since we are fallible, nothing we can grasp can make beliefs certain in principle. So, if justification is understood as an internal notion, i.e. as something we must have a full grasp of, the conclusion is that knowledge requires a fourth condition, beside belief, truth and justification. But what could it be? On the other hand, if we found a condition which entailed the truth of our beliefs, wouldn’t that condition more rightly deserve to be called justification? for it would accomplish the task for which justification is needed. Now, because of human fallibility, any such condition must be something external, transcending in principle subjective grasp. The other possible strategy is therefore adopting an external and objective notion of justification, already hinted at in Plato’s Meno. This can be done, for instance, assuming that a belief is justified when it is the last ring of a causal chain beginning with its truthmaker (A. Goldman). The idea that justification is provided by a causal chain justification has a number of problems: it cannot account for our knowledge of non physical (e.g. mathematical) facts, and of future facts, nor for the (possibly) non physical nature of some of the items from which beliefs are produced, such as perceptual experiences, mathematical intuitions, further beliefs, and inferences. Thus I use instead the more general notion of a productive chain, understood as a chain (a) whose links can be both physical causes, and such non physical processes as perceptual experiences, mathematical intuitions, further beliefs and inferences, and (b) which can originate either in a past truthmaker, or in the past cause of a future truthmaker, so that the latter can be inferred from the former. Moreover, as shown by some counterexamples in the literature, causal chains include “awkward” or “deviant” chains, which intuitively do not warrant knowledge. I then introduce the stronger notion of a normal productive chain, in which each ring is of a type normally produced (directly or indirectly) by facts of the type of the truthmaker, and I show that this nicely accounts for this class of purported counterexamples. Nonetheless, the etymological sense of the word ‘justification’ carries the deontological idea that justification ensures the subject’s right, or at least excuse, for holding a belief, and in this sense it must consist of internal evidences. Furthermore, I have already granted that such internal items, as perceptual experiences, further beliefs, and inferences, are typically part of productive chains. Finally, other counterexamples (e.g., BonJour’s clairvoyance example) show that sufficiently concordant internal evidences are also a necessary condition for knowledge. The conclusion is therefore that knowledge requires both an objective external condition, the productive chain, entailing truth, and a subjective condition, the internal evidences, which fall short of entailing truth, so accounting for human fallibility. At this point a terminological choice is open: wishing to keep only the purely subjective deontological sense of ‘justification’, one can use this term for the internal evidence, and claim that knowledge requires an additional objective condition, beside justification, viz. the productive chains. But since the existence of a productive chain entails the truth of the belief, conditions will still be three: belief, justification and productive chain. Otherwise, one may wish to keep both the senses traditionally attached to justification: bestowing a subjective right or excuse, and providing an objective warrant. Hence, justification will require both the internal evidences and the productive chain, and knowledge will require just two conditions, belief and justification, for justification in this sense entails truth.