Bacon's Novum Organum of 1620: the critique of Aristotelian syllogism, the theory of idols, and the inductive method with tables of presence, absence, and degrees.

What Was Francis Bacon’s Scientific Method?

Francis Bacon’s Novum Organum — “New Organon,” published in 1620, with the full title Novum Organum Scientiarum, or “New Instrument of the Sciences” — was one of the founding documents of modern empirical science. The book was the manifesto of the new method of natural philosophy, and it was the first systematic attempt to articulate the principles of what we would now call scientific inquiry. The book is named in deliberate echo of Aristotle’s Organon, the collection of works on logic; Bacon’s book was meant to replace Aristotelian logic with a new, more useful, more practical method of reasoning about nature. This page looks at Bacon’s scientific method: the critique of Aristotelian syllogism, the theory of idols, the inductive method with tables of presence, absence, and degrees, and the broader program of the Great Instauration. The biographical and contextual notes are on the Bacon and Descartes page. The contrast with Descartes’ deductive method is treated in How Did René Descartes Contribute to the Scientific Revolution?. The broader context of the Scientific Revolution is in the page on the key figures and the philosophy of science section.

The Critique of Aristotelian Syllogism

The first half of the Novum Organum is a critique of Aristotelian logic, the basis of the university curriculum in the early seventeenth century. The Aristotelian logic was, in Bacon’s view, sterile: it was a system of words that had no contact with experience, and it could not produce new knowledge. The syllogism — the logical form in which a conclusion is drawn from two premises — was, in Bacon’s view, useless for the investigation of nature. It could only be used to make explicit what was already implicit in the premises, and it could not, in itself, generate new knowledge of the world. The critique was not new. The humanists of the Renaissance had long attacked the scholastic tradition, and the recovery of the Greek and Roman classics had made the scholastic tradition look, parochial. But Bacon’s critique was, more systematic. He argued that the syllogism was not just useless, but positively harmful: it created the illusion of knowledge without the substance of knowledge, and it trained the mind to mistake verbal disputes for real inquiry. The proper aim of natural philosophy, he argued, was not to dispute about words, but to understand the world and to use that understanding to relieve the human condition. Bacon’s critique of the syllogism was the foundation of the empirical tradition in British natural philosophy. The Royal Society, founded in 1660, was in part a Baconian institution: its members took as their motto nullius in verba, “take nobody’s word for it,” and they pursued a program of careful observation and experiment that was the realization of Bacon’s program. The wider context of the empiricist tradition is treated in the philosophy of science section.

The Theory of Idols

The most famous part of the Novum Organum is the theory of idols, which is set out in Aphorisms 39–68 of Book I. The idols are the false notions, the deep-seated errors, that warp human reasoning. Bacon distinguished four kinds. Idols of the Tribe (idola tribus) are the errors that are common to all human beings, by virtue of the limitations of the human mind. The mind, Bacon argued, is not a mirror that passively reflects the world. It is an active instrument that distorts what it perceives. It tends to see more order and regularity in the world than is actually there; it tends to be impressed by striking, novel, or beautiful phenomena, and to overlook familiar ones; it tends to extend its understanding of familiar things to unfamiliar ones, by analogy, even when the analogy is not justified; and it tends to be moved by hope, fear, desire, and other passions, in ways that distort judgment. The idols of the tribe are the human condition. Idols of the Cave (idola specus) are the errors that are peculiar to individual human beings, by virtue of their particular educations, temperaments, and circumstances. The metaphor is Platonic: each person, like a prisoner in a cave, sees the world through the distorting lens of his own particular situation. A person who has been trained in one discipline will tend to interpret the phenomena of another in terms of the first; a person who is inclined to optimism will tend to see the world in a more favorable light than it deserves; a person who is inclined to pessimism will tend to see the world in a less favorable light. The idols of the cave are the idiosyncrasies of the individual. Idols of the Marketplace (idola fori) are the errors that arise from the misuse of language. Words, Bacon argued, are not neutral instruments; they carry the marks of the common usage that produced them, and they impose that usage on the things they are used to describe. The word “heavy,” for instance, carries with it the connotation of falling downward, and it imposes that connotation on any phenomenon to which it is applied. The word “light” carries the connotation of moving upward. The result is that we tend to think of heaviness and lightness as intrinsic properties of bodies, when they are, in fact, relations between bodies and the center of the Earth. The idols of the marketplace are the distortions of language. Idols of the Theatre (idola theatri) are the errors that arise from the uncritical acceptance of philosophical systems. The metaphor is from the theatre: the philosopher is like a playwright who creates a world out of his own imagination, and the audience takes the world to be the real one. The Aristotelian philosophy, the Pythagorean philosophy, the alchemical philosophy, and the religious philosophy are, in Bacon’s view, all examples of theatrical idols. They are systems of words that have no contact with the world, and they have dominated the human mind for centuries. The idols of the theatre are the most insidious of the four, because they are the most systematic. The theory of idols was a kind of cognitive psychology avant la lettre. It identified, with some precision, the ways in which the human mind goes wrong in its attempts to understand the world. The theory was an anticipation of the modern theory of cognitive bias, and it was one of the most durable contributions of Bacon’s philosophy.

The Inductive Method

The second half of the Novum Organum (Aphorisms 95–121) sets out the inductive method, the procedure that Bacon proposed to replace Aristotelian syllogism. The method was a description of the way that the new natural philosophers should proceed, and it was a critique of the way that the old natural philosophers had proceeded. The method begins with the careful collection of instances, the cases in which the phenomenon under study is observed. The instances are to be tabulated in three ways. The Table of Presence lists the cases in which the phenomenon is observed. If the phenomenon is heat, the table lists all of the cases in which heat is observed: the sun, fire, hot water, friction, animal bodies, and so on. The Table of Absence lists the cases in which the phenomenon is not observed, even though conditions similar to those in the Table of Presence are present. The table lists all of the cases in which heat is not observed, despite conditions that would, according to received opinion, produce heat: the moon, a cold body, a non-friction situation, and so on. The Table of Degrees (or Comparison) lists the cases in which the phenomenon is present in different degrees, and correlates the degree with the presence or absence of other conditions. If heat varies, the table lists the conditions that vary with it: the proximity of the sun, the intensity of friction, the temperature of the surrounding body, and so on. The method, applied to the tables, was supposed to yield, by a kind of exclusion, the “form” of the phenomenon. The form of heat, for instance, was the condition that was always present when heat was present, always absent when heat was absent, and varied in degree with heat. The form of heat, on Bacon’s analysis, was a particular kind of molecular motion — a claim that, anticipates the modern kinetic theory of heat. The method was the first systematic attempt to articulate the principles of empirical inquiry. The tables of presence, absence, and degrees are the ancestor of the modern method of controlled experiment, in which variables are systematically varied and the effects are observed. The method was also, too rigid to be applied in practice: it assumed that the relevant variables could be enumerated in advance, and that the “form” of the phenomenon could be reached by a kind of mechanical exclusion. In practice, scientists proceed by hypothesis formation and testing, not by mechanical exclusion. But the spirit of the method — careful observation, systematic variation, gradual ascent to general principles — was the spirit of the new science.

The Great Instauration

The Novum Organum was meant to be the second part of a much larger work, the Instauratio Magna, the “Great Instauration.” The Instauration was Bacon’s plan for a comprehensive reconstruction of the sciences, in six parts: a classification of the sciences; the new instrument, or the inductive method; the phenomena of the universe; the intellect, or the ladder of the intellect; the forerunners, or anticipations of the new philosophy; and the new philosophy, or active science. Bacon published the Advancement of Learning (1605) as a kind of introduction, the Novum Organum (1620) as the second part, and the New Atlantis (1627) as a kind of epilogue. The other parts were never written. The Instauration was a project that was too large for a single lifetime. The Instauration was the founding document of the Royal Society, and of the modern idea of a research institution. The New Atlantis, in particular, was a description of a fictional institution, Salomon’s House, that pursued the Baconian program of inductive natural philosophy. The institution was the blueprint for a research university, with laboratories, observatories, libraries, and gardens, and with a division of labor among its members. The Royal Society, founded in 1660, was in part a realization of Bacon’s vision, and the idea of a research institution has been a central feature of modern science ever since.

The Reception of Bacon’s Method

Bacon’s method was widely discussed in the seventeenth and eighteenth centuries, but it was not, in practice, systematically applied. The natural philosophers of the period, including Galileo, Descartes, Boyle, Hooke, Huygens, and Newton, all proceeded by a combination of observation, hypothesis, and mathematical analysis that was more flexible than Bacon’s strict induction. The method was a description of what the new natural philosophers were doing, but it was not, in any strict sense, a prescription for what they should do. The reputation of Bacon’s method has varied over time. In the nineteenth century, under the influence of John Stuart Mill and the British empiricist tradition, Bacon was celebrated as the prophet of the inductive method, and the Novum Organum was widely cited as the founding document of modern science. In the twentieth century, under the influence of the history and philosophy of science, Bacon’s reputation suffered. The method was, too rigid, and it did not, in practice, produce the results that Bacon had promised. The philosophers of science, including Popper, argued that science proceeds by hypothesis and refutation, not by mechanical induction. The truth, as usual, lies somewhere in between. Bacon was right to insist on the centrality of observation and experiment in natural philosophy, and he was right to insist on the sterility of the Aristotelian-Scholastic tradition. He was wrong to insist on the strict inductive method as the only valid procedure, and he was wrong to think that the form of a phenomenon could be reached by mechanical exclusion. The proper method of natural philosophy is a combination of careful observation, controlled experiment, hypothesis formation, and mathematical analysis. The combination is closer to Newton than to Bacon, but it is the descendant of the Baconian program.

The Legacy of the Novum Organum

The legacy of the Novum Organum is the modern empirical tradition. The book was the first systematic articulation of the principles of empirical inquiry, and it was the founding document of the modern experimental science. The four idols of the tribe, the cave, the marketplace, and the theatre have become a part of the standard vocabulary of cognitive criticism. The tables of presence, absence, and degrees have become the ancestor of the modern method of controlled experiment. The New Atlantis has become the founding document of the modern research institution. The combination of these legacies is the legacy of the Scientific Revolution. The empirical tradition, the critique of authority, the appeal to experience, the idea of a research institution, the conviction that nature can be understood and used for the benefit of mankind: these are the contributions of the Scientific Revolution, and they are the contributions of Francis Bacon. See the philosophy of science section and the Scientific Revolution: Origins, Causes, and Timeline. The contrast with the Cartesian deductive method is treated in How Did René Descartes Contribute to the Scientific Revolution?.

What Was Francis Bacon's Scientific Method?