What is the (historical and theoretical) relationship between the scientific experimental method and the two espistemologies of empiricism and rationalism?

I can read here and there that the experimental method is really linked to the philosophy of empiricism. Also, Francis Bacon, the founder of empiricism, is also the founder of the experimental science.

But the physiologist Claude Bernard is also considered the father of the experimental method, and had harsh words against empiricism: "Empiricism is a narrow and abject dungeon from which the imprisoned mind can only escape on the wings of a hypothesis." (Deepl translation checked by myself from French: "L’empirisme est un donjon étroit et abject d’où l’esprit emprisonné ne peut s’échapper que sur les ailes d’une hypothèse").

And we can read elsewhere than Descartes understood the experimental method better than Francis Bacon himself.

Here a quote on the link between empiricism and the scientific method (The Open University: 3 Enlightenment, science and empiricism):

The Enlightenment's dedication to reason and knowledge did not come out of the blue. After all, scholars had for centuries been adding to humanity's stock of knowledge. The new emphasis, however, was on empirical knowledge: that is, knowledge or opinion grounded in experience. This experience might include scientific experiments or firsthand observation or experience of people, behaviour, politics, society or anything else touching the natural and the human. For any proposition to be accepted as true, it must be verifiable, capable of practical demonstration. If it was not so verifiable, then it was an error, a fable, an outright lie or simply a hypothesis. Although Enlightenment thinkers retained a role for theoretical or speculative thought (in mathematics, for example, or in the formulation of scientific hypotheses), they took their lead from seventeenth-century thinkers and scientists, notably Francis Bacon (1561–1626), Sir Isaac Newton and John Locke (1632–1704), in prioritising claims about the truth that were backed by demonstration and evidence. In his ‘Preliminary discourse’ to the Encyclopédie, d'Alembert hailed Bacon, Newton and Locke as the forefathers and guiding spirits of empiricism and the scientific method. To any claim, proposition or theory unsubstantiated by evidence, the automatic Enlightenment response was: ‘Prove it!’ That is, provide the evidence, show that what you allege is true, or otherwise suspend judgement.

And also this quote from a SE user's (@J D) answer (of the question "What does rationalism prove that empiricism can not?"), which also to me points to an association between empiricism and experimental method:

So, a rationalist tends to rely on reason or logic, and an empiricist tends to rely on experimentation or trial and error. Obviously, both are necessary aspects of good thinking if one is interested in connecting one's private world to one's public world. These two traditions in the 21st century have largely developed into an alliance between mathematical and scientific theories across a broad range of disciplines.

Nb: I am not very sure of the difference between "experimental science", "experimental method", and "scientific method".

My question is different from "What does rationalism prove that empiricism can not?" because: (1) It takes here also an historical point of view, and aims to be more precise in terms of which author said what, instead of focusing specifically on the purely philosophical/metaphysical arguments (2) It tackles the terms and concepts of "empirical method", "scientific method", etc. (3) It is not oriented in one way or another

I believe the granularity nature of questions (1) and (2) can be quite beneficial to the community, since I am not sure, as the answers to the question already indicate, that all the facts and terminology at stake are obvious.

  • "Francis Bacon was not the founder of empiricism, and was not the founder of the experimental science." He was no scientist at all, but a natural philosopher. See Francis Bacon Jan 29 at 10:36
  • Do you have an idea of the different centuries of Bacon and Claude Bernard life? Jan 29 at 10:37
  • Descartes was a mathematician and he was also an experimenter. Jan 29 at 10:38
  • Does this answer your question? How do rationalists justify the scientific method?
    – Conifold
    Jan 29 at 10:39
  • @Conifold It does not because the question in this post is very philosophical, although I am here more on history of philosophy and science
    – Starckman
    Jan 29 at 11:09

2 Answers 2


The terms you are using are somewhat ambiguous. Here is a bit of clarification:

The first Empiricists were physicians of classical Greece who opposed the theories of the sort used by Hippocratic physicians. Opposition to theories is not the same thing as modern empiricism, but it is related.

In modern philosophy, empiricism is usually defined as the position that all of our information comes from experience, and rationalism is the position that disagrees with this---that says we have some other source of information. These are fairly abstract positions that don't have much to do with the experimental method.

In the early modern age, empiricism/rationalism is also linked to certain specific thinkers during the Scientific Revolution. Descartes, Spinoza, and Leibniz are usually listed as rationalists and Locke, Berkeley and Hume are listed as empiricists. To the extent that the words are linked to these philosophers, "empiricism" and "rationalism" are broader and less precise than the technical definition.

Modern readers seem to read "experience" in these texts as meaning something like "observation and experiment", but that is not how the word is used in philosophy (or at least wasn't from the beginning of the modern era to the 1920s. I can't think of any authors using the word more recently, so I can't extend the claim beyond that). In this tradition, experience is not experiment; experience is a subjective event like the experience of beauty in a sunrise or the experience of pain. Rather than being hard-nosed realists, the early empiricists tended to be idealistic and/or skeptical, to doubt the very existence of the physical world and/or the very possibility of science. The empiricists argued that all we have is subjective experience, so we have no good reason to think that anything besides subjective experience exists. Thus the empiricists were critics of science while the rationalists where the supporters of science.

Claude Bernard probably understood this, because the quote you give sounds like it was directed at the Berkeley/Hume sort of empiricist.

In the late 19th and early 20th centuries, there was a skeptical movement against scientific theories that postulated unobservable entities such as atoms and aether. Ernst Mach and Pierre Duhem are two physicists associated with this movement. They were sometimes called empiricists as opposed to the rationalists who accepted the introduction of unobservable entities. Mach is also famous for criticizing Archimedes' rationalist proof of the Law of the Lever.

In the early 20th century where there were efforts by some philosophers and mathematicians such as Frege and Russel to prove that mathematics did not need Kant's synthetic a priori knowledge (which is epistemologically rationalist) because it could be based on pure logic. They were called Logicists.

The Logicist movement spawned Logical Positivism, also called Logical Empiricism, which is probably where the current epistemological definitions come from. However the Logical Positivists, unlike the earlier idealist empiricists, tended to take the material world and the rationality of science as givens. Their project was to justify science based on pure observation and experiment. There is still some ambiguity in that movement, and Rudolph Carnap in Aufbau specifically says that in his theory, the basic data of the world can be understood in either an idealist or materialist sense. The movement collapsed in time, partly because they were unable to bridge the gap between subjective experience and matter without resorting to rationalism.

In contemporary amateur philosophy and history of science, "empiricism" is often treated as a sort of synonym for "scientific" or "using observation and experiment". This use has been used to shoehorn the distinction into Plato (rationalist) vs. Aristotle (empiricist), although the definition doesn't fit very well. In this usage, it has also been claimed that classical Greek science was "rationalist" vs. modern science which is "empiricist", meaning that the Greeks didn't use observation and experiment but modern science does (a claim that is based on truth but is rather deceptive at face value). However, this use of "empiricism/rationalism" is at odds with the philosophical distinction, because rationalists (in the epistemological sense) don't deny the importance of observation and experiment; they only claim that not everything we claim to know can be accounted for with experience.

If someone says that Francis Bacon is the founder of empiricism, they are probably thinking of the contemporary non-epistemological definition. Bacon was famous for his (unsuccessful) attempt to come up with a system of inductive logic, and inductive logic is often used as a ground or justification for the experimental method. However, Bacon was probably a rationalist in the epistemological sense.

Although these things grow and develop over time, if you want to credit a single individual with creating the scientific method, it would have to be Isaac Newton. It was his Principia that first spelled out a systematic method of observation, hypothesis, and confirmation.

So with that background, here are the answers to your questions:

  1. There is no relationship between the scientific method and the epistemological positions of empiricism vs. rationalism except that strict empiricism makes it impossible to justify experiment as a way to acquire knowledge of the world.

  2. In the general non-epistemological literature, empiricism is associated with science because it is basically defined as the position that observation and experiment are necessary to investigate the natural world while rationalism is defined as the position that the world can be intuited purely through thought (which is practically the reverse of the epistemological definitions). By these new definitions, it is doubtful that there have ever been any thoroughgoing rationalists any time in history except for some esoteric mystics.

  3. "Experimental science" is generally used as a contrast with "theoretical science". It names the difference between a scientist who sits at his desk with a notepad and one who stands at a lab bench with a beaker. Both types of scientist agree that the final test of theory is experiment.

  4. "Experimental method" is a general term to describe investigating nature by experiments.

  5. "Scientific method" is a a more specific term that invokes some sort of specific method observation, hypothesis, and experiment to confirm/refute the hypothesis.

  • Thank you very much. "Called the father of empiricism, Sir Francis Bacon is credited with establishing and popularizing the “scientific method” of inquiry into natural phenomena." lib-dbserver.princeton.edu/visual_materials/maps/websites/…
    – Starckman
    Jan 29 at 11:02
  • "Thus the empiricists were critics of science while the rationalists where the supporters of science." I am surprised, because the analytic philosophy, and with it the logical positivism, also called logical empirism, developed out of empirism, and these trends are very supportive of science
    – Starckman
    Jan 29 at 11:15
  • 1
    @starckman, those are both good points. I've updated my answer in response. Sorry for the large additions, but you made me realize I had given short shrift to the empiricist movements of the turn of the 19th century. Jan 29 at 18:12
  • 1
    @starckman, as to who is idealist and who is skeptical, it's not that clearcut. Hume expressed some doubts about the physical world, and Berkeley expressed some misgivings about science. As to Newton, he may be a "materialist empiricist" by today's non-epistemological definition, but I don't think there was any such thing in his day. Jan 30 at 4:53
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    @starckman Do I personally think that? Yes. Once you decide that experience is the sole source of knowledge, you are confronted with the fact that experience is an inherently subjective event and that we have no way to know whether our perceptions are caused by an external world or by something entirely different, like a computer or the mind of God. Jan 30 at 13:37

Empericism claims knowledge is post-experience. Rationalism is the opposite view that knowledge is pre-experience. Experiments can be thought of as experiences and are aimed at acquiring knowledge post-experiment i.e. post-experience (is part of empiricism).

The experimental method is simply a list of criteria that havta be met for an activity to be deemed an experiment.

The scientific method is empiricism's blue-eyed boy. It obviously includes experiments but there's also hypotheses which are explanatory frameworks for predictions in re experiments.

Are experiments part of rationalism? Well, we do test for consistency.

  • "empiricism's blue-eyed boy" what does that mean?
    – Starckman
    Jan 29 at 11:20
  • Who introduced "The experimental method"? Francis Bacon?
    – Starckman
    Jan 29 at 11:20
  • Who introduced "The scientific method"? Claude Bernard?
    – Starckman
    Jan 29 at 11:21

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