My aim in this book is to explain and defend a rationalist conception of a priori justification and knowledge: a view according to which there is genuine a priori justification that is not limited in its scope to tautologies or matters of definition. Though taken largely for granted throughout most of the history of philosophy, such a view has fallen into increasing disrepute in the last two centuries and has been generally repudiated in recent times. Nonetheless, as explained further in Chapter 1, it is arguably difficult or impossible to make good sense of most if not all claims of empirical knowledge, and indeed of reasoning generally, while eschewing any a priori appeal. What this indicates, I think, is that the prevailing forms of empiricism are in fact untenable, and that a re-examination of rationalism is sorely needed.
Though this book is not primarily meta-philosophical in character, the need for an account of genuine and non-tautological a priori justification seems to me especially urgent for philosophy itself. While it is not my purpose to argue the matter in detail here, my conviction is that philosophy is a priori if it is anything (or at least if it is anything intellectually respectable); and that the practice of even those who most explicitly reject the idea of substantive a priori justification inevitably involves tacit appeal to insights and modes of reasoning that can only be understood as a priori in character, if they are justified at all.
The main conclusion of the preceding chapter was that the distinctively epistemological objections to rationalism, while perhaps not entirely without force, are very far from being decisive. Indeed, it is more natural to construe the epistemological objections, taken as a group, as merely revealing various limitations of our a priori capacities. These limitations are no doubt unfortunate, but they cannot plausibly be construed as serious reasons for taking the quixotic step of abandoning rational thought altogether, or at least any claim of cogency on its behalf – which is what we have seen that the rejection of rationalism would amount to.
In any case, though such a conjecture would be impossible to verify, it seems to me likely that the reasons for the widespread dismissal of rationalism lie on the metaphysical rather than the epistemological side of the ledger. I have already voiced the suspicion that the intellectual motives for the rejection of rationalism lie more in the realm of fashion than of argument, but even the relevant fashions seem primarily metaphysical in character. My purpose in this chapter is to examine and evaluate some of these metaphysical fashions and objections.
As was the case with the epistemological objections, the metaphysical objections to rationalism are only rarely spelled out and developed in any detail.
THE NEED FOR THE A PRIORI
Perhaps the most pervasive conviction within the Western epistemological tradition is that in order for a person's belief to constitute knowledge it is necessary (though not sufficient) that it be justified or warranted or rationally grounded, that the person have an adequate reason for accepting it. Moreover, this justifying reason must be of the right sort: though one might accept a belief for moral reasons or pragmatic reasons or religious reasons or reasons of some still further sort and be thereby in a sense justified, such reasons cannot satisfy the requirements for knowledge, no matter how powerful, in their own distinctive ways, they may happen to be. Knowledge requires instead that the belief in question be justified or rational in a way that is internally connected to the defining goal of the cognitive enterprise, that is, that there be a reason that enhances, to an appropriate degree, the chances that the belief is true. Justification of this distinctive, truth-conducive sort will be here referred to as epistemic justification.
Historically, most epistemologists have distinguished two main sources from which the epistemic justification of a belief might arise. It has seemed obvious to all but a very few that many beliefs are justified by appeal to one's sensory (and introspective) experience of the world.
Our discussion of a priori justification so far has been in the main relentlessly abstract, with only a few of the most obvious examples to enliven the way. While this seems to me appropriate where it is the very existence of non-tautological a priori justification that is at issue, it does leave the issue of the scope of a priori justification almost entirely unillumined. For all that has been argued so far, it would be possible that a priori justification of the rationalist kind, though genuinely existent, is confined entirely to the general kinds of examples discussed in §4.2. And if this were so, then such justification, though perhaps important in these limited areas, would have little significance for human knowledge in general and would in particular do almost nothing to solve the problem of observation-transcendent inference raised in §1.1. Radical empiricists would indeed be mistaken in their central claim, but their error would be of little consequence; their general epistemological position would still be closer to the truth than that of the rationalist in the ways that matter most.
My conviction is that, on the contrary, rationalistic a priori justification is of crucial importance for epistemology and indeed for philosophy generally.
In this appendix, I will try to say something about the implications of non-Euclidean geometry and especially its role in the theory of General Relativity for a rationalist view of a priori knowledge. There can be little doubt that from a historical standpoint, the development of non-Euclidean geometries was a major factor in producing the widespread conviction that a rationalist position is untenable. Euclidean geometry was after all the most striking example of seemingly substantive a priori knowledge of independent reality, invoked by Kant as one of the crucial examples of the synthetic a priori. But, according to the simplest version of the standard story, within a few years after Kant, the development of non-Euclidean geometry by Lobashevsky and others showed that Euclidean geometry was not necessarily true of physical space, making it an empirical issue which geometry correctly describes the physical world. And eventually, or so the story goes, this empirical question was resolved by General Relativity in favor of a version of Riemannian or elliptical geometry and against Euclid. The suggested further argument, often left fairly implicit, is that if the rationalist view fails in this paradigmatic case, there can be no good reason for thinking that it will in the end be any more acceptable elsewhere.
As explained in the previous chapter, the moderate empiricist position on a priori knowledge holds that while such knowledge genuinely exists and has occasional importance in its own distinctive way, it is nonetheless merely analytic in character – that is, very roughly, merely a product of human concepts, meanings, definitions, or linguistic conventions. Such knowledge thus says nothing substantive about the world, and its justification can be accounted for without appealing to anything as problematic as the rationalist idea of rational insight into the character of an sich reality. Indeed, as we shall see later in this chapter, it is this alleged capacity to provide an unproblematic explanation of a priori justification that constitutes the main argument for moderate empiricism, even in the face of recalcitrant rationalist counterexamples.
For much of this century, this general sort of position had the status of virtually unquestioned orthodoxy for most philosophers in the Anglo-American tradition; and despite the recent prominence of the radical empiricist views that will be discussed in the next chapter, it seems likely that moderate empiricism continues to be the most widely held view of the nature and status of a priori justification. What is profoundly misleading about the foregoing picture, however, is the suggestion that there is anything like one reasonably specific position that can be identified as moderate empiricism.
This chapter will consider a number of epistemological objections to the moderate rationalism outlined in the previous chapter. What qualifies these objections as distinctively epistemological in character is their underlying concern with whether and why rational insight, as characterized in the preceding chapter, can provide epistemic justification for a belief, in the sense specified in 1.1 above: that is, can yield a compelling reason for thinking that the belief in question is true. There can be little doubt that an apparent rational insight provides some sort of reason for believing the proposition in question. A belief arrived at in this way is certainly not merely arbitrary or capricious and may indeed be psychologically compelling to the point of being inescapable. But none of this shows that the believer in question possesses a genuinely epistemic reason for his belief, and it is this that the objections to be considered attempt to call into question.
I have already remarked that despite the widespread conviction that rationalism is untenable, fully developed and articulated objections to rationalism are difficult to find. This is especially true of the epistemological objections that are the subject of this chapter. Thus, while it is unlikely that anyone who has thought very much about the issue of a priori justification will find the general drift of these objections to be utterly unfamiliar, the specific presentations offered here are largely my own attempts to tease out and develop lines of thought that are usually only briefly hinted at in the literature or, more often, in oral discussion (thus the relative dearth of specific citations).
The argument of the previous chapters leads to the striking or perhaps even startling conclusion that empiricist positions on a priori justification and knowledge, despite their apparent dominance throughout most of the twentieth century, are epistemological dead ends: the moderate empiricist attempt to reconcile a priori justification with empiricism by invoking the concept of analyticity does not succeed, indeed does not really get off the ground; and the radical empiricist attempt to dispense entirely with such justification ends in a nearly total skepticism. The indicated conclusion is that a viable non-skeptical epistemology, rather than downgrading or rejecting a priori insight, must accept it more or less at face value as a genuine and autonomous source of epistemic justification and knowledge. This is the main thesis of epistemological rationalism and also the central thesis of the present book.
Obviously, however, such a result can be no more than tentative until the rationalist view has been explored more fully and shown to be defensible. For even if the objections to the two positive empiricist views are indeed decisive, as claimed here, the possibility remains that the negative empiricist claim is correct: that a priori justification as understood by the rationalist simply does not exist.
RADICAL EMPIRICISM AND SKEPTICISM
The conclusion of the preceding chapter was that the moderate empiricist approach to a priori justification does not succeed. Moderate empiricism turns out on examination to be in effect a mere schema for a position, one that is apparently incapable of being satisfactorily fleshed out into a realized view and that owes most of its initial appeal to this schematic character (and, I have suggested, to a pervasive failure to distinguish clearly between the various attempted realizations thereof).
What alternative then is left for the empiricist? The answer is both stark and obvious: if a priori justification cannot be accommodated within the empiricist framework in the way that the moderate empiricist attempts, then it must apparently be repudiated outright if empiricism is to be sustained. Such a course would have had very little appeal to most of the historical advocates of empiricism, with the single, somewhat problematic exception of Mill, but it has been seriously advocated in recent times, mainly by Quine and his followers. While this Quinean view seems to me very difficult to take seriously, the present chapter will be devoted to an attempt to understand and evaluate it.
Though it is not always so regarded, radical empiricism as thus understood is of course a form of skepticism, indeed seemingly one of the deepest and most threatening forms of skepticism.
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