[Cross-posted at Philosophical Pontifications]
Brand Blanshard (The Nature of Thought, vol. 2 , Ch. XXXII, “Concrete Necessity and Internal Relations”; Reason and Analysis, Ch. XI, “Necessity in Causation”) and A.C. Ewing (Non-Linguistic Philosophy: Ch. VI, “Causation and Induction”) gave similar arguments for the existence of “logical necessity” in causation. (Given that their views of logic are somewhat unorthodox by the standards of analytic philosophers, I think it would be more accurate and less confusing to talk of metaphysical necessity in causation, which I will do in what follows.) A “rational reconstruction” of their arguments goes something like this: If causal connections are not metaphysically necessary, the fact that similar effects follow upon similar causes, or that there are certain, seemingly exceptionless regularities in nature (which can be expressed in laws of nature) is quite remarkable. If “anything can cause anything”, as Humeans sometimes say, we have a tremendous coincidence, “an outrageous run of luck”, as Blanshard puts it (The Nature of Thought, vol. 2, Ch XXXII, “Concrete Necessity and Internal Relations”, p. 505 of the second edition), comparable to rolling a die and getting a 4 a trillion times in a row. But if causal connections are metaphysically necessary, we have a good explanation for the fact that similar effects follow upon similar causes, or that there are exceptionless regularities in nature: they obtain because they must. If events of type B necessarily follow upon events of type A, any token A event will be followed by a token B event. (Not, of course, that we can perceive this necessity: we could only perceive it if we had some kind of direct insight into the natures of type A events and type B events.) Granting that, it follows that we can justify instances of inductive inference that fit the following schema: Events of type A have always been followed by events of type B, hence, events of type A will always be followed by events of type B.
Brand Blanshard (The Nature of Thought, vol. 2 , Ch. XXXII, “Concrete Necessity and Internal Relations”; Reason and Analysis, Ch. XI, “Necessity in Causation”) and A.C. Ewing (Non-Linguistic Philosophy: Ch. VI, “Causation and Induction”) gave similar arguments for the existence of “logical necessity” in causation. (Given that their views of logic are somewhat unorthodox by the standards of analytic philosophers, I think it would be more accurate and less confusing to talk of metaphysical necessity in causation, which I will do in what follows.) A “rational reconstruction” of their arguments goes something like this: If causal connections are not metaphysically necessary, the fact that similar effects follow upon similar causes, or that there are certain, seemingly exceptionless regularities in nature (which can be expressed in laws of nature) is quite remarkable. If “anything can cause anything”, as Humeans sometimes say, we have a tremendous coincidence, “an outrageous run of luck”, as Blanshard puts it (The Nature of Thought, vol. 2, Ch XXXII, “Concrete Necessity and Internal Relations”, p. 505 of the second edition), comparable to rolling a die and getting a 4 a trillion times in a row. But if causal connections are metaphysically necessary, we have a good explanation for the fact that similar effects follow upon similar causes, or that there are exceptionless regularities in nature: they obtain because they must. If events of type B necessarily follow upon events of type A, any token A event will be followed by a token B event. (Not, of course, that we can perceive this necessity: we could only perceive it if we had some kind of direct insight into the natures of type A events and type B events.) Granting that, it follows that we can justify instances of inductive inference that fit the following schema: Events of type A have always been followed by events of type B, hence, events of type A will always be followed by events of type B.
Our argument for this schema is neither deductive nor inductive: We have not deduced, and neither have we seen through “rational insight”, that it is necessary that type A events will always be followed by type B events based on knowledge of their natures, nor have we concluded that type A events will always be followed by type B events just because they have always been so followed in the past. Our argument is rather this: In certain cases we take ourselves to have established that every observed event of type A has been followed by an observed event of type B. We also note that, since type A events are observed very frequently, it is extremely unlikely (though possible) that their association with type B events is a matter of chance. So there are two alternatives: Either the association is an astronomically improbable coincidence, or there is a necessary connection between them, albeit one that we are not able to discern. Next we consider the principle of Inference to the Best Explanation (IBE): This principle says, very roughly, that if we have multiple hypotheses vying to account for some phenomenon, it is most reasonable to accept the hypothesis which best explains it as being true. And if we think that having any explanation is rationally preferable to having none—assuming we have no evidence which rules out all of the candidate explanations, or which renders them extremely improbable—then IBE tells us that it is always more reasonable to accept an explanatory hypothesis over a non-explanatory one. Since coincidence is no explanation, in the present case IBE counsels us to accept the hypothesis that there is a metaphysically necessary connection between type A events and type B events. Because of this necessary connection, we can conclude that in the future type A events will always be followed by type B events, just as they always have been. So we have justified our inductive schema neither deductively nor inductively, but by IBE.
Note that in the above we have not invoked the principle of sufficient reason or the idea that every event must have a cause; we are only saying that it is more reasonable to believe in a necessary connection than an astronomical coincidence. Thus the objections that can be raised against them cannot be raised against the present argument.
At this point you might be wondering about IBE. What justifies us in accepting it? Why should we believe that the hypothesis which best explains a phenomenon is the most rationally acceptable one? I think it can be justified, although it can neither be justified deductively, nor inductively, nor by IBE. It cannot be justified deductively because IBE is clearly not a truth of logic or mathematics. It also cannot be justified inductively, at least not by the kind of inductive inference being considered on the present account, because we are trying to use IBE to justify those inductive inferences, and to use them to justify IBE would be circular. Finally, to use IBE to justify itself would also be circular. Instead, I think IBE can be justified “transcendentally”. It is essentially a case of “this or nothing”. If we did not regard better explanations as more rationally acceptable, it would be extremely difficult, if not impossible, to justify anything that goes beyond our beliefs about elementary logic and our immediate perceptual experiences. (For one instance of this problem, see my post over at Philosophical Pontifications on Bertrand Russell’s five minute hypothesis. ) This does not refute skepticism, but it does show that anyone who rejects skepticism is entitled to use IBE; or, at the very least, that they cannot consistently criticize those who do use it.
“But how does God figure into all this?”, you might ask. If you want to know, stay tuned for Part 2!
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