Online research in philosophy

There has been a significant shift in the discussion of a priori knowledge. The shift is due largely to the influence of Quine. The traditional debate focused on the epistemic status of mathematics and logic. Kant, for example, maintained that arithmetic and geometry provide clear examples of synthetic a priori knowledge and that principles of logic, such as the principle of contradiction, provide the basis for analytic a priori knowledge. Quine’s rejection of the analytic-synthetic distinction and his holistic empiricist account of mathematic and logical knowledge undercut the traditional defenses of the a priori in two ways. First, one could no longer defend the view that mathematical and logical knowledge is a priori solely by rejecting Mill’s inductive empiricism. Moreover, holistic empiricism proved to be a more challenging position to refute than inductive empiricism. Second, the rejection of the analytic-synthetic distinction blocked an alternative defense of the a priori status of mathematics and logic that appealed to their alleged analyticity.

Certainty and doubt -- Sources of conviction -- Rationalism -- Rationalism versus relativism in morals -- Induction and deduction -- The retreat from certainty -- Utilitarianism -- Kantian ethics -- Empiricism -- Beyond empiricism -- Objectivity -- Materialism and dualism -- Morality for naturalists -- Deep illusions -- Realism.

This paper criticizes the epistemological doctrine of moderate rationalism that has been defended in recent years by such writers as Laurence BonJour, Alvin Plantinga, and George Bealer. It is argued that this new form of rationalism is really no better than the old one and that the key claim common to both---that intuition or rational insight provides a satisfactory basis for a priori knowledge---is untenable. Most of the criticism is directed specifically against Laurence BonJour’s recent “dialectical” defense of the doctrine. Since BonJour’s defense is essentially an attempt to show how a priori knowledge is possible, an alternative, empiricist view of a priori knowledge is presented that eludes his objections and is supported by the criticism brought against moderate rationalism.

Most current theories of meaning and mental content accept externalism. One of its forceful exponents is Ruth Garrett Millikan. She argues that externalism leads to the abandonment of "the last myth of the given", that is, of the idea that identity of meaning and mental content is somehow unproblematically given to us, and that we can easily recognize the sameness of meaning and mental content. If one refuses such a "mythical" giveness or meaning rationalism, one has to admit that there is no logical possibility known a priori . The paper tries to show that even if one abandons meaning rationalism one can still hold that there are logical possibilities known a priori . The claim is defended by arguing that a priori knowledge is not completely independent from experience and does not demand the absolute transparency of meaning from the first-person point of view. A priori knowledge requires only a priori justification, that is, such a justification that is based merely on relations between meanings or contents.

Radical empiricism is the view that a person's experiences (sensory and introspective), or a person's observations, constitute the person's evidence. This view leads to epistemic self-defeat. There are three arguments, concerning respectively: (1) epistemic starting points; (2) epistemic norms; (3) terms of epistemic appraisal. The source of self-defeat is traced to the fact that empiricism does not count a priori intuition as evidence (where a priori intuition is not a form of belief but rather a form of seeming, specifically intellectual as opposed to sensory). Moderate rationalism, by contrast, avoids self-defeat.

In this paper I argue for a priori conjectural scientific knowledge about the world. Physics persistently only accepts unified theories, even though endlessly many empirically more successful disunified rivals are always available. This persistent preference for unified theories, against empirical considerations, means that physics makes a substantial, persistent metaphysical assumption, to the effect that the universe has a (more or less) unified dynamic structure. In order to clarify what this assumption amounts to, I solve the problem of what it means to say of a theory that it is unified. There are, I argue, eight different kinds of unity important in theoretical physics, all varieties of one basic idea. This provides us with a precise way of partially ordering physical theories with respect to their degree of unity. It also leads to a hierarchical view of physics, according to which physics makes a number of increasingly insubstantial metaphysical assumptions concerning the comprehensibility and knowability of the universe. Two of these are identified as constituting a priori conjectures. I conclude by arguing that the view developed in the paper resolves the traditional clash between empiricism and rationalism in the philosophy of science, and has important implications for science, and for academic inquiry more generally.

In his essay “Logical Empiricism”, in the anthology Twentieth Century Philosophy, Professor Feigl writes: “All forms of empiricism agree in repudiating the existence of synthetic a priori knowledge.” Schlick makes the same point even more forcibly: “The empiricism which I represent believes itself to be clear on the point that, as a matter of principle, all propositions are either synthetic a posteriori or tautologous; synthetic a priori propositions seem to it to be a logical impossibility.” The denial of synthetic a prioris is a major thesis of the logical empiricist position, being found in the writings of most of the leaders of the movement. The reason for its importance is fairly clear. It provides a formula on which the empiricists can base their critique of traditional philosophy. To use Ayer's phrase, denial of the synthetic a priori results in “the elimination of metaphysics”. The philosophical tradition to which the empiricists are opposed and whose “metaphysics” they wish to eliminate can be called, somewhat loosely, rationalism.