There is also the question whether metaphysical arguments are inductive or deductive or whether they have some logical form peculiar to themselves. It is obvious that much metaphysical reasoning is, or purports to be, reasoning in the strict sense, which is to say that its form is deductive. Arguments like the first cause argument for God’s existence claim to be demonstrations; their exponents believe that anyone who commits himself to the truth of the premises stands logically committed to the truth of the conclusions. This claim can stand, even if it turns out that the project to set out metaphysical results in the geometrical manner is a mistake. It may be impossible to model metaphysics on mathematics, but that does not make particular metaphysical arguments any less deductive.
As regards inductive arguments, it would be odd to find a metaphysician contending, as, for example, historians regularly do, that p is true and q is true and therefore it is reasonable to conclude that r is true. To assess probabilities in the light of established facts is too cautious for the average metaphysical mind. Yet it would be wrong to deny that metaphysicians are preoccupied with facts. Their objective is to give a reasoned account of what exists or obtains, and for this purpose attention to fact is of course indispensable. It figures in metaphysical thinking at two stages. First, at the beginning, when the metaphysician is concerned to formulate his main thesis; here there is a move from what holds in a restricted sphere (the sphere of physics, for example) to what is supposed to hold generally, a move that is possible only if the theorist concerned has an interest in the sphere in question. To arrive at his own position the metaphysician must extrapolate from what goes on outside metaphysics, and this means that he must be sensitive to significant developments in at least some of the main fields of learning and areas of practical activity. But he needs this extra-philosophical knowledge for a second purpose too: in estimating the success of his own theories. In principle he must show that his interpretation of experience covers the facts in an adequate way, and for this purpose what experts in the different spheres take to be established is of crucial importance. Metaphysics is not an empirical science—the element of speculation it includes is too strong for that—but the metaphysician can no more ride roughshod over facts than the scientist can. At the least he must explain away phenomena that seem to count against his thesis, or indicate how they might be explained away. Whether he explains or explains away, he needs to know what the main phenomena are.
Finally, it is sometimes said that metaphysics can make use of a form of argument that is neither deductive nor inductive but transcendental; a transcendental argument is supposed to proceed from a fact to its sole possible condition. A transcendental argument is simply a form of deduction, with the typical pattern: only if p then q; q is true; therefore, p is true. As this form of argument appears in philosophy, the interest, and the difficulty, reside not in the movement from premises to conclusions, which is absolutely routine, but in the setting up of the major premises—in the kinds of things that are taken as starting points. In Kant’s case, it was such things as the possibility of pure mathematical knowledge, the possibility of making objectively true statements, the fact that there is a unitary system of time. Kant purported to prove a number of surprising propositions by the use of transcendental arguments; he tried to commend major premises such as his arguments about causality and substance by showing what would result if the protasis (i.e., p) did not hold. What he had to say under this head has attracted particular interest in recent years. It seems clear, however, that from the logical point of view no special significance attaches to this form of argument. Although Kant had been successful in demonstrating that a sufficient is also a necessary condition, he did not make clear why it should be taken as the sole such condition. There is an important gap in his reasoning here, as there is in that of other metaphysical writers. Criticisms of metaphysics
Metaphysics has many detractors. The man who aspires “to know reality as against mere appearance,” to use Bradley’s description, is commonly taken to be a dreamer, a dupe, or a charlatan. Reality in this context is, by the metaphysician’s own admission, something that is inaccessible to sense; as Plato explained, it can be discovered only by the pure intelligence, and only if the latter can shake itself free of bodily encumbrances. The inference that the metaphysical world is secret and mysterious is natural enough. Metaphysics in this view unlocks the mysteries and lets the ordinary man into the secrets. It is, not to put too fine a point on it, a study of the occult. Metaphysics as knowledge of the supersensible
That there are aspects of metaphysics that lend colour to this caricature can scarcely be denied. The language of Plato, in particular, suggests an absolute distinction between the deceitful world of appearances, which can never be an object of knowledge, and the unseen world of Forms, each of which is precisely what it appears to be. Plato urged his readers not to take seriously the things of sense; he told them that everything having to do with the senses, including the natural appetites and the life of the body, is unreal and unimportant. The philosopher, in his view, needs to live an ascetic life, the chief object of which is to cultivate his soul. Only if he does this, and follows a rigorous intellectual training, has he any hope of getting the eye of his soul fixed on true reality and so of understanding why things are what they are.
Yet even this program admits of an innocuous, or relatively innocuous, interpretation. The “dialectician,” as Plato called his metaphysical philosopher, is said in one place to be concerned to “give an account,” and the only things of which he can give an account are phenomena. Plato’s interest, despite first appearances, was not in the unseen for its own sake; he proposed to go behind things visible in order to explain them. He was not so much disdainful of facts as critical of accepted opinions; his attack on the acquiescence in “appearances” was an attack on conventional wisdom. That this was so comes out nowhere more clearly than in the fact that his targets included not just beliefs about what there is but also beliefs about what is good. It is the opinions of the many that need correction and that can happen only if men penetrate behind appearances and lay hold on reality.