Rationalism and modal knowledge.
| Autor | McLeod, Stephen K. |
| Cargo | Report |
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Modal Realistas and Modal Epistemology
According to the semantic realist about modality, there are modal truths: as opposed, say, to all modal discourse being systematically false, as the error theorist has it, of non-factual, as the projectivist has it. We require an epistemology for modality only if semantic realista holds, so semantic realism is presupposed for the purposes of this article. Sernantic realism about modality is a necessary but non-sufficient condition for ontological realista about it. For the ontological realist the distinctively modal element to the modal truth is grounded in mind-independent reality (rather than, for example, being grounded merely in convention). (1)
Much current work in the epistemology of modality focuses on metaphysical modality, taking after Kripke's approach to a posteriori necessity. For Kripke, we know the necessary a posteriori by modus ponens inference from an a priori major premise and an empirical minor premise. For example, following the exposition of Hale (1996, p. 492):
If a chemical stuff has a given chemical formula then it has that chemical formula of necessity.
Water is the chemical stuff with chemical formula [H.sub.2]O.
Water is necessarily [H.sub.2]O.
It is the truth, rather than the necessity, involved in the necessary a posteriori that is known a posteriori. The a posteriority of the conclusion is the result of "spill-over" from the empirical minor premise. The modal major premises, which Elder (2004, p. 5) dubs "template truths", are held to be known a priori (e.g., Kripke 1971, p. 88). Rationalist accounts of modal epistemology entail that at least some modal knowledge is essentially a priori. (2) However, we may be tempted, with Ellis (2001), Miscevic (2003) and perhaps Elder (2004), to be realists about natural necessity but opponents of a priori modal knowledge construed rationalistically. (3) The main airo of this article is to suggest that such temptation should probably be resisted. A positive modal epistemology for ontological realista about the modal is likely to be a rationalist one. In this section, some varieties of realista and anti-realism about the modal are explained. Some rationalist theses in the epistemology of modality are outlined and some putative combinations of ontological realista about the modal with anti-rationalism are summarized. Sections 2 and 3 argue against two such combinations. It is concluded, minimally, that those who contend that ontological realista about modality can be combined with the wholesale rejection of modal rationalism have not established their view. Moreover, it is difficult to see how they might do so.
In the context of the epistemology of modality, an epistemic conception of the distinction between rationalism and empiricism is of primary concern. Rather than being about the origins of our ideas, this conception of the distinction concerns epistemic priority. An item of propositional knowledge, p, is epistemically prior to an item of propositional knowledge, q, if and only if knowledge that q depends on knowledge that p and knowledge that p does not depend on knowledge that q.
Weak rationalism about the modal results from the combination of the following theses. First, there are items of modal knowledge and (at least) some of them depend on some items of a priori modal knowledge. Second, for some of those items of a priori modal knowledge, no item of a posteriori knowledge is epistemically prior. The weak rationalist's first thesis can be embraced by non-Quinean empiricists. Ir is the second thesis which provides the distinctively rationalist element to weak rationalism. (4) The second thesis does not require that the relevant a priori modal knowledge is epistemically prior to the relevant a posteriori modal knowledge, but ir precludes the a posteriori modal knowledge from being epistemically prior to the a priori modal knowledge. The Quinean empiricist will reject the second thesis, partly on the basis that there is no a priori knowledge. Empiricist foundationalists like Ayer (1950) will reject it on the grounds that empirical knowledge is epistemically prior to a priori modal knowledge. For the rationalist foundationalist, like Descartes, some a priori knowledge has epistemic priority over all other items of propositional knowledge. Weak rationalism is compatible with, but does not entail, rationalist foundationalism.
Strong rationalism about the modal claims that there are items of modal knowledge and that for every item of modal knowledge, p, there is some item of modal knowledge, q, such that knowing p requires a priori knowledge of q. When knowing that p requires a priori knowledge that q, then either the epistemic priority is in a q-to-p direction or else q and p are one-and-the-same item of knowledge. Strong rationalism debars there from being any item of modal knowledge which lacks a basis in the a priori. For the strong rationalist, there can be no exclusively empirical process resulting in modal knowledge. Some extra-empirical knowledge is required whenever a modal truth is known.
Kripke (1971; 1980) set out to refute the claim, central to the orthodox logical positivist approach to modality, that the necessary and the a priori are co-extensive. (5) Kripke takes the modal major premises in arguments to modal knowledge a posteriori to be a priori. If Kripke accepts that for some of those items of a priori modal knowledge, there is no item of set of items of a posteriori knowledge epistemically prior to the a priori modal knowledge, then he is (at least) a weak rationalist. (6) Strong anti-rationalism rejects weak rationalism. I distinguish between two ontologically realist, strongly anti-rationalist strategies concerning the modal. One is based on confirmationism about the modal; the other, on the appeal to the explanatory purchase of the modal. (7)
Confirmationism tries to ward off epistemological worries by providing an empirical account of how we can tell the difference between what must be and what merely is. The clairn is that knowledge of metaphysical modality does not require the a priori. Elder (1992; 2004) is what I am calling a "confirmationist". The strategy of the appeal to the explanatory purchase of the modal, on the other hand, claims that modalising has explanatory content with respect to the empirical world. If either strategy works, then a key motive for rationalism, namely the thesis that the modal is empirically empty, is undercut. (8)
Before proceeding further, let us review some philosophical theories concerning matters ontological and epistemological. We will focus, in particular, on the relationships between these theories. We are concerned with the three ontologically realist approaches. The ontological realist may hold that a model of knowing which has it that all our knowledge is derived via our causal interaction with the world is more epistemologically suspect than modality. That is to say, it may be claimed that we can justifiably be more certain that we know that a given modal claim is true than that we know to be true an epistemological theory which brings our claim to modal knowledge into doubt or which, if our claim to knowledge were true, could not explain its truth. (9)...
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