Claim that inference in accordance with some version of the inductive principle is, if not logically valid, at least rationally legitimate.
Objections to it include those mentioned under uniformity of nature and Goodman’s paradox.
R Swinburne, ed., The Justification of Induction (1974)
Francis Bacon, articulating inductivism in England, is often falsely stereotyped as a naive inductivist. Crudely explained, the “Baconian model” advises to observe nature, propose a modest law that generalizes an observed pattern, confirm it by many observations, venture a modestly broader law, and confirm that, too, by many more observations, while discarding disconfirmed laws. Growing ever broader, the laws never quite exceed observations. Scientists, freed from preconceptions, thus gradually uncover nature’s causal and material structure. Newton’s theory of universal gravitation—modeling motion as an effect of a force—resembled inductivism’s paramount triumph.
Near 1740, David Hume, in Scotland, identified multiple obstacles to inferring causality from experience. Hume noted the formal illogicality of enumerative induction—unrestricted generalization from particular instances to all instances, and stating a universal law—since humans observe sequences of sensory events, not cause and effect. Perceiving neither logical nor natural necessity or impossibility among events, humans tacitly postulate uniformity of nature, unproved. Later philosophers would select, highlight, and nickname Humean principles—Hume’s fork, the problem of induction, and Hume’s law—although Hume respected and accepted the empirical sciences as inevitably inductive, after all.
Immanuel Kant, in Germany, alarmed by Hume’s seemingly radical empiricism, identified its apparent opposite, rationalism, in Descartes, and sought a middleground. Kant intuited that necessity exists, indeed, bridging the world in itself to human experience, and that it is the mind, having innate constants that determine space, time, and substance, and thus ensure the empirically correct physical theory’s universal truth. Thus shielding Newtonian physics by discarding scientific realism, Kant’s view limited science to tracing appearances, mere phenomena, never unveiling external reality, the noumena. Kant’s transcendental idealism launched German idealism, a group of speculative metaphysics.
While philosophers widely continued awkward confidence in empirical sciences as inductive, John Stuart Mill, in England, proposed five methods to discern causality, purportedly how genuine inductivism exceeds mere enumerative induction. Meanwhile, in the 1830s, opposing metaphysics, Auguste Comte, in France, explicated positivism, which, unlike Bacon’s model, emphasizes predictions, confirming them, and laying scientific laws, irrefutable by theology or metaphysics. Interpreting experience to reveal uniformity of nature, indeed, and thereby justify enumerative induction, Mill accepted positivism—the first modern philosophy of science. Also a political philosophy, it posed scientific knowledge as ultimately the only knowledge.
Nearing 1840, William Whewell, in England, deemed the inductive sciences not so simple, after all, and argued for recognition of “superinduction”, an explanatory scope or principle invented by the mind to unite facts, but not present in the facts. John Stuart Mill rejected Whewell’s hypotheticodeductivism as science’s method. Yet Whewell believed it to sometimes, upon the evidence, potentially including unlikely signs, including consilience, render scientific theories that are probably true metaphysically. By 1880, C S Peirce, in America, had clarified the basis of deductive inference and, although acknowledging induction, also proposed a third type of inference. Peirce called it “abduction”, now otherwise termed IBE, inference to the best explanation.
Since the 1920s, rebuking metaphysical philosophies, the logical positivists, accepting hypotheticodeductivism on the origination of theories, sought to understand scientific theories as provably false or true as to merely empirical facts and logical relations. Thus, they launched verificationism. In its milder variant, Rudolf Carnap tried, but always failed, to formalize an inductive logic whereby a universal law’s truth via observational evidence could be quantified by “degree of confirmation”. Asserting a type of hypotheticodeductivism termed falsificationism, Karl Popper from the 1930s onward especially attacked inductivism and its positivist variants as untenable. In 1963, Popper called enumerative induction “a myth”, a deductive inference from a tacit theory explanatory. Gilbert Harman soon explained enumerative induction as a masked outcome of IBE.
Thomas Kuhn’s 1962 book, a cultural landmark, explains that periods of normal science as but paradigms of science are each overturned by revolutionary science, whose radical paradigm becomes the normal science anew. Kuhn’s thesis dissolved logical positivism’s grip on Western academia, and inductivism fell. Besides Popper and Kuhn, other postpositivist philosophers of science—including Paul Feyerabend, Imre Lakatos, and Larry Laudan—have all but unanimously rejected inductivism. Among them, those who have asserted scientific realism—that scientific theory can reliably approximate true understanding of nature’s unobservable aspects—have tended to claim that scientists develop approximately true theories about nature through IBE. And yet IBE, which, so far, cannot be trained, lacks particular rules of inference. By the 21st century’s turn, inductivism’s heir was Bayesianism.
From the 17th to the 20th centuries, inductivism was widely conceived as scientific method’s ideal. Even at the 21st century’s turn, popular presentations of scientific discovery and progress naively, erroneously suggested it. Meanwhile, the 20th was the first century producing more scientists than philosopherscientists. Earlier scientists, “natural philosophers,” could ponder and debate philosophies of scientific method. Einstein remarked, “Science without Epistemology is—in so far as it is thinkable at all—primitive and muddled”.
Particularly after the 1960s, scientists became unfamiliar with the historical and philosophical underpinnings of their won research programs, and often unfamiliar with logic. Scientists thus often struggle to evaluate and communicate their own work against question or attack or to optimize methods and progress. In any case, during the 20th century, philosophers of science accepted that scientific method’s truer idealization is hypotheticodeductivism, which, especially in its strongest form, Karl Popper’s falsificationism, is also termed deductivism.
Inductivism infers from observations of similar effects to similar causes, and generalizes unrestrictedly—that is, by enumerative induction—to a universal law.
Extending inductivism, Comtean positivism explicitly aims to oppose metaphysics, shuns imaginative theorizing, emphasizes observation, then making predictions, confirming them, and stating laws.
Logical positivism, rather, would accept hypotheticodeductivsm in theory development, but nonetheless sought an inductive logic to objectively quantity a theory’s confirmation by empirical evidence and, additionally, objectively compare rival theories.
Whereas verification of a theory would prove it, confirmation simply supports it evidentially. But to reason from confirmation to verification is the deductive fallacy called “affirming the consequent”: If A, then B; indeed B; therefore A. This is illogical since even if B holds, A could be due instead to X or Y or Z, or XYZ combined. A is but one possibility among potentially infinite. Or the sequence A trailed by B could be consequence of U—a factor utterly undetected—whereby B always after A could be simply constant conjunction but not causality, and U could potentially cease, disconnecting A from B