What Is Empiricism and Why Did It Matter?
Empiricism holds that knowledge comes from sensory experience. It was a defining commitment of the Scientific Revolution, advanced by Bacon, Galileo, and Newton.
What Is Empiricism and Why Did It Matter?
Empiricism is the philosophical view that all knowledge of matters of fact is ultimately grounded in sensory experience. Where rationalist philosophers held that certain truths could be known by reason alone, independently of experience, empiricists held that the contents of the mind, including its most abstract ideas, are derived from the impressions made on the senses by the external world. The Scientific Revolution was, in part, a triumph of the empirical approach to nature, and the principal philosophical opponents in the seventeenth century — the rationalist Descartes and the empiricist Bacon — defined the agenda of modern philosophy of science.
The Definition of Empiricism
The word empirical comes from the Greek empeiria, meaning experience. An empiricist is, broadly, a philosopher who takes experience — observation, experiment, the testimony of the senses — to be the source of our knowledge of the natural world. There are several forms of empiricism, of varying strength. Modest empiricism holds that some knowledge of nature can be had by reason alone, but that scientific knowledge in particular must be grounded in observation and experiment. Strong empiricism holds that all knowledge of matters of fact is ultimately derived from experience, and that there are no innate ideas or rational insights into the nature of things. Radical empiricism extends the empirical approach even to mathematical and logical knowledge, holding that these too are ultimately derived from experience. Most natural philosophers of the Scientific Revolution were modest empiricists, accepting that observation and experiment are the proper grounds for natural philosophy while allowing that mathematics itself might be known by reason. The most influential empiricists of the period — Roger Bacon, Francis Bacon, Galileo, Robert Boyle, John Locke, and Isaac Newton — were empiricists in this modest sense.
The Background: From Roger Bacon to Francis Bacon
The empirical tradition in European philosophy is conventionally traced back to Roger Bacon (c. 1214–1294), the Oxford Franciscan who emphasized the importance of experience and experiment in the pursuit of natural knowledge. Roger Bacon’s Opus Majus (1267) argued that there were four sources of human knowledge: authority, reason, custom, and inspiration, but that only experience could verify and certify what the others proposed. He was also a careful experimenter in optics, proposing, for example, the use of lenses to aid weak sight — a possibility that be realized in the telescope and microscope. The empirical tradition was continued in the Renaissance by figures such as Leonardo da Vinci, whose notebooks combined careful observation with mechanical reasoning, and by the practitioners of the mechanical arts — the instrument-makers, navigators, and engineers — for whom empirical knowledge was a practical necessity. The decisive statement of the empirical program, however, came from Francis Bacon (1561–1626), the English philosopher, jurist, and Lord Chancellor. Bacon’s Novum Organum (1620) — the “new organon,” a deliberate echo of Aristotle’s Organon — argued that the Aristotelian-Scholastic logic was inadequate to the task of natural philosophy, and proposed a new method based on the gradual ascent from particular observations to general axioms. Bacon’s method, with its emphasis on the systematic collection of instances, the tabulation of natural phenomena, and the gradual elimination of false generalizations, was enormously influential in England and, eventually, throughout Europe.
Galileo and the New Empiricism
Galileo Galilei (1564–1642) is sometimes presented as the embodiment of the new empiricism, and with some justice. His Two New Sciences (1638) is built around the report of carefully designed experiments on the motion of falling bodies, the strength of materials, and the motion of projectiles. Galileo’s experiments were not the casual observations of the natural world; they were deliberate interventions, designed to test specific hypotheses, and the results were stated in mathematical form. Yet Galileo’s empiricism was combined with a strong mathematical rationalism. He insisted that the book of nature is written in mathematical characters, and that the proper aim of natural philosophy is the discovery of mathematical laws. Galileo’s method was, in this sense, a synthesis of empirical and rationalist elements. The combination is characteristic of the new science, and it is examined in detail in the article on What Is the Scientific Method?.
The Royal Society and the Experimental Tradition
The empirical tradition was institutionalized in the Royal Society of London, founded in 1660. The Society’s motto — Nullius in verba, “On no one’s word” — expressed the commitment to direct investigation of nature rather than reliance on ancient authority. The Society met regularly to witness and discuss experiments, and it published the Philosophical Transactions, the first scientific journal, beginning in 1665. The experimental tradition associated with the Royal Society was developed by Robert Boyle (1627–1691), the Anglo-Irish chemist and natural philosopher. Boyle’s experimental work on the vacuum, the air pump, and the chemistry of acids and alkalis exemplified the new empirical method. His book The Sceptical Chymist (1661) argued that chemistry should be based on experimental investigation rather than on the alchemical tradition. Boyle also articulated a sophisticated form of mechanical philosophy that treated chemical combination as a matter of the size, shape, and motion of corpuscles.
Locke’s Essay Concerning Human Understanding
The most influential philosophical statement of the empiricist position in the early-modern period was John Locke’s Essay Concerning Human Understanding (1690). Locke, who had been a student at Oxford and a member of the Royal Society, argued in the Essay that the mind is, at birth, a tabula rasa — a blank slate — and that all of its ideas are derived from experience. The two sources of experience, for Locke, were sensation (the impression made on the senses by external objects) and reflection (the mind’s awareness of its own operations). Locke’s empiricism had an enormous influence on the growth of modern philosophy, and it set the agenda for the empiricist tradition in the eighteenth century — most importantly in the works of George Berkeley and David Hume. The contrast with the rationalist tradition of Descartes and Leibniz is examined in the article on Rationalism vs Empiricism.
Newton and the Mature Empiricism
Isaac Newton’s philosophical method, as articulated in the Principia (1687) and the Opticks (1704), was a sophisticated form of empiricism. Newton’s famous “Rules of Reasoning in Philosophy” — the four methodological rules with which he prefaced the Principia and the Opticks — defined a middle path between naive induction and dogmatic deduction. The fourth and most important of the rules reads: “In experimental philosophy we are to look upon propositions inferred by general induction from phenomena as accurately or very nearly true, notwithstanding any contrary hypotheses that may be imagined, till such time as other phenomena occur, by which they may either be made more accurate, or liable to exceptions.” This was an important philosophical move. It acknowledged that scientific knowledge is not certain, that it is liable to revision in the face of new evidence, and that the proper way to evaluate a scientific theory is by its agreement with phenomena. At the same time, it held that the agreement is a good reason to take the theory to be (provisionally) true. Newton’s method, in this sense, was a form of empirical realism — a commitment to the existence of a world that scientific theories describe, combined with a careful, fallibilist method for investigating that world.
Why Empiricism Mattered
The empirical approach mattered because it changed the standards by which natural philosophy was judged. Where the Aristotelian-Scholastic tradition had valued consistency with ancient authority and logical coherence, the new empirical tradition valued agreement with the phenomena, the success of predictions, and the possibility of independent replication. The change in standards made possible the dramatic expansion of knowledge that characterized the Scientific Revolution and its aftermath. The empirical approach also mattered because it was deeply connected with the practical concerns of the period. Empirical knowledge was usedful knowledge, in the Baconian sense. The instruments, techniques, and methods developed by the new empirical natural philosophy — telescopes, microscopes, barometers, air pumps, thermometers — were powerful tools of investigation and, increasingly, instruments of practical power. The empirical tradition was, in this sense, an integral part of the technological transformation of early modern Europe.
The Limits of Empiricism
The empirical tradition also had its critics, and they raised important questions that are still debated today. The Scottish philosopher David Hume, in the Enquiry Concerning Human Understanding (1748), argued that induction — the inference from observed cases to unobserved cases — is not rationally justified, since it assumes that the future will resemble the past. Hume’s critique raised the so-called “problem of induction,” which has never been fully resolved. The question of how empirical evidence can confirm or disconfirm scientific theories is also a major theme in twentieth-century philosophy of science, in the work of Karl Popper, Thomas Kuhn, Imre Lakatos, and others. These debates are direct continuations of the questions raised by the Scientific Revolution, and they are part of the longer history of the empirical tradition. The broader context is examined in the page on Philosophy of Science and in the broader Scientific Revolution overview.