Baruch Spinoza and Robert Boyle were giants in their respective fields during the burgeoning examination of the relationship between philosophy and science which characterized the Scientific Revolution. The prevailing physical philosophy of the time was mechanical philosophy, which was to displace the long-held Aristotelian traditions.[1] At that time Henry Oldenberg was Secretary (he was also the first) of the Royal Society, the authoritative academic organization which pursued scientific development, and it was Oldenberg who initiated a correspondence with Spinoza, due to the former’s pursuit of all persons of contemporary academic excellence (W.38). Although Oldenberg corresponded with Spinoza in twenty-eight letters, he served as intermediary between Boyle and Spinoza for five of them (W.34).[2] In 1661 Oldenberg sent Spinoza Boyle’s “Certain Physiological Essays” (which contained his nitre experiment) and elicited Spinoza’s reaction to it (Gabbey 1996, p. 149). The question “Is matter qualitative or quantitative?” was central to this series of letters exchanged between them.
In his introduction to a collection of Boyle’s work, Stewart maintains that “he had a fruitless exchange on scientific matters with Spinoza…” (S.xxxi). However, this paper attempts to outline some of the benefits which can be extracted from the correspondence of two important figures who stressed different aspects and approaches to our understanding of the universe. The first section of this paper will set forth the physical theories of Spinoza and Boyle. The second part will take into account their correspondence on such topics, focusing on Boyle’s nitre experiments. The third part of the paper will attempt to show that neither Spinoza nor Boyle achieved a conclusive demonstration of their positions (respective to the exchange) based upon analysis of their exchanges on the experiment in question. The fourth and final part will summarize a list of philosophical points which are useful to philosophy, in particular the philosophy of science and the physical world.
Boyle was primarily a scientist and a defender of the mechanical philosophy (with his corpuscular variation) and claimed that “the material world is made up of corpuscles of the one impenetrable matter possessing a definite shape and size and capable of motion” (Chalmers 2009, p. 97). He was a pioneer of experimental science, and acknowledged two forms of knowledge: “intermediate causes” involved in experimental science which were empirically accessible, and ultimate mechanical truth, which was not (ibid). He agreed with the proposition of Baconian science – that experiments measured observable bodies and detectable properties (Chalmers 2009, p. 99). He restricted science to material terms, with no appeal to God in relation to experiments (God exists but experimentalism’s scope does not include Him) (Chalmers 2009, p. 100).
However, his experiments with pneumatics involved pressure, etc. and were not strictly mechanical (this was acknowledged by Boyle). He realized that all of the scientific phenomena of the time were not adequately covered by the mechanical philosophy alone (for example, in describing the cohesion of a snowball, etc.) (Chalmers 2009, p. 104). He thus claimed that experiments are subject-specific (Chalmers 2009, p. 98). In his time, Thomas Hobbes, a fellow mechanical philosopher, criticized Boyle for his descriptions of the “elasticity” of air, and maintained that Boyle had provided no explanation of how it moves itself and thus had contradicted mechanical philosophy. Boyle himself admitted that it was not a mechanical explanation, yet he had shown experimentally that air has a spring and that this quality can be appealed to (Chalmers 2009, p. 109). Boyle maintained that work needed to be guided by “grand hypotheses”, but under scrutiny, he changed its aim to the establishment of “matters of fact” (ibid).
He was more than ever opposed to going back to Aristotlean forms and the Greek position of giving an account of the reality behind the appearances, or “primary affections” (Chalmers 2009, p. 105). Instead, like Bacon, he felt that science was merely a set of “histories”, and that experimentation was different than mechanical philosophy. The highest level of causes may be important for human beings to discover, but in actuality they may be different from what we suppose them. He cautions that “we may aspire to, but must not always require or expect, such a knowledge of things as is immediately derived from first principles.” (Chalmers 2009, p. 106). So experimental science had “subordinate principles” and “intermediate causes” only (ibid).
He acknowledged that experimental knowledge is not infallible, and that unknown causes can lead to errors. Therefore its primary function was to rule out untenable alternatives and refine the theories (Chalmers 2009, p. 109). He saw that at the extreme end there were metaphysics which were not possible to be tested (Chalmers 2009, p. 110). The main difference between a theory of mechanical philosophy and experiments was that the former required more proof, since it was not a “matter of fact” (Chalmers 2009, p. 111). Boyle claimed that mechanical philosophy was simply a useful tool, like a cipher in solving a puzzle (the idea that evidence was more a function of accommodation versus confirmation of the truth) (Chalmers 2009, p. 112).
On the other hand, Gabbey maintains that it is difficult to know the exact methodology of Spinoza’s physical theory and notes his absence in the authoritative “Dictionary of Scientific Biography” as proof of his not being considered a “proper scientist” (although some works do include him) (Gabbey 1996, pp. 142-148). Savan maintains that for Spinoza, science was “incidental” to major concerns of salvation, ethics, etc. (Savan 1986, p. 100). Spinoza’s physical science was loosely Cartesian (in both content and method) and indeed he reworked Descartes’s “Principles of Philosophy” (Gabbey 1996, p. 155). Like Descartes, he derived a priori his natural laws, claiming they were merely attributes of God (Gabbey 1996, p. 156). He believed that there was only extension and mode – that it is size, shape, and motion alone which distinguish substances, and that individual bodies are individuated by motion and rest alone. He believed that bodies are not made of different substances but are modifications of a single substance. He believed even that man himself was a part of nature, and that there was no such thing as “interference” with “nature”, that everything which happens in nature is a modification of one substance (Gabbey 1996, pp. 180- 1). He was however, not an Occasionalist (there was no outside influence of God) (Garber 1988, p. 593) rather bodies were infused with inherent activity (Garber 1988, p. 594).
Like the prevalent theories of the day, Spinoza’s physical theory was dismissive of occult qualities, yet it was also distinguished by its antagonism to experimentalism. Spinoza maintained that empirical findings at best give examples of what reason already demonstrates, and that experimentation was useful but not conclusive. Experimentation was insufficient to gain absolute knowledge and so had limited utility. Although more aloof from practical science, Spinoza nonetheless kept abreast of the latest developments and corresponded with many contemporary figures on the subject (Gabbey 1996 p. 148). He wanted to strive towards a “unified body of interrelated demonstrative truths” and sought in his methodology “the Whole” as opposed to Atomism (Gabbey 1996, pp. 156-7). He agrees with the Baconian notion that science was merely “natural and experimental histories” and felt that natural interpretation can be likened to Scriptural interpretation – that there ought to be a basis from which to derive interpretation (Gabbey 1996, p. 170). Also like Bacon, he believed in the fact that experiential vaga, or random experimentation, could only obtain so much – that it must be directed to produce any results (Gabbey 1996, p. 172).
The result was that Spinoza wanted to “eliminate the explanatory appeal to incorporeal things in the physical world, without eliminating those things themselves” (Garber 1988, p. 591). He believed in a parallel of bodies and thought and God/Nature had infinite attributes (ibid). Spinoza’s “true Method” was “the knowledge alone of the pure understanding”. Thus experimentation can only confirm incontrovertible logical truths, and vaga was “not determined by the intellect” (Gabbey 1996, pp. 171-2). Perceptions lead to inferences, yet counter-examples can be produced, so they are not infallible (ibid). Experimentation is useful but not conclusive (Gabbey 1996, p. 175). He actually saw no distinction between everyday experience and scientific reasoning (Savan 1986, p. 108).
E.W. von Tschirnhaus, in his own correspondence with him, criticized Spinoza’s “Method”, claiming that “Method is nothing but a reflexive knowledge” (Gabbey 1996, p. 177) and that “Method” doesn’t give new information but only what is already established while experimentation can give only sensory knowledge and not causes (ibid). Maull asserts that Spinoza seeks certainty and needs only a few experiments to “know” something (given his philosophically tight deductive approach) and raises the question: “Why given Spinoza’s apparent interest in experiment, is he so estranged from it philosophically?” (Maull 1986, p. 7). She concludes, “Consequently, what we get from Spinoza is a physical theory…that is neither drawn from nor applicable to a concrete embodiment in particular natural phenomena.” (Maull 1986, pp. 8-10).
One of Boyle’s essays discussed in particular was “On Nitre, Fluidity, and Firmness” (W.84). It described the following experiment: a glowing coal was placed upon on nitre (saltpeter and potassium nitrate) which produced fixed (fixed nitre, potash, and potassium carbonate) and volatile (spirit of nitre and nitric acid) parts. (Gabbey 1996, p. 178). The parts were then recombined and quantitatively almost the same amount of nitre was recovered. Boyle concluded that nitre is a chemical compound (not a mechanical mixture) consisting of parts substantially different in physical and chemical natures. He observed that the spirit was acidic and the fixed portion was alkaline. These differences in turn upheld the corpuscular theory of nature (individual parts were maintained) but not substantial forms, given the altered substances (Gabbey 1996, p. 177-8).
From the outset of their correspondence, Spinoza felt that Bacon had “more than adequately demonstrated” substantial qualities based on mechanics (motion, shape, etc.) (Gabbey 1996, p. 171). In Letter IV, Spinoza makes no distinction between the parts derived in the experiment and sees no reason for Boyle’s conclusion. He goes on to give his own mechanical explanation that they are all the same (W.85-86). He also conducts his own experiments and further explains Boyle’s observations of taste and flammability (W.87-89). He goes on to decry the superfluity of experimentation and holds that common observations suffice as well (W.91). He says, “It does not immediately follow that a particle of matter acquires a new shape because it is joined to another: it only follows that it becomes larger, and this is sufficient to produce the effect which the very illustrious author seeks in this section.” (W.93). Spinoza’s objection was that Boyle needed a further experiment to actually prove that nitre and spirit of nitre were different. He maintained that fixed nitre was only an “impurity” in the original. He further demanded that multiple experiments were required to test if indeed the same quantity was always reproduced (Gabbey 1996, p. 178). Spinoza went on to theorize that nitre and its spirit had fixed, rigid, carrot-shaped parts (the same). Boyle had claimed that he had reached “primary and mechanical affectations” but Spinoza claimed that Boyle had not give a mechanical account – that a conclusive account should show geometrical particle differentiation. (Gabbey 1996, p. 179).
Oldenberg replies in Letter XI that: The object that he [Boyle] had set before himself was not so much to show that this was a really philosophic and perfect analysis of Nitre, but rather to explain that the common Doctrine of Substantial Forms and Qualities which is also accepted in the Schools, rests on a weak foundation, and that what they call the specific differences of things can be reduced to the magnitude, motion, rest and position of their parts.[…] Meanwhile, he thinks that your suppositions about the process, your view that the fixed salt of the Nitre is as it were its dregs, and other similar suppositions, are gratuitous and unproved.” (W.110-111). He agrees with Spinoza that nitre and its spirit are the same, but holds they are not the same forms due to the observations (W.111-12). He goes on to clarify Boyle’s intentions – that he did not think other writers in his time had clearly given mechanical explanations and only sought to improve the situation and concludes: “Our Boyle belongs to the number of those who have not so much confidence in their reason as to wish that Phenomena should agree with their reason.” (W.112). He also claims there is a difference between common experiments where there are unknown Natural contributions and isolated experiments which rule them out (ibid).
In Letter XIII, Spinoza says that he did not think Boyle’s motive was only to disavow the doctrine of substantial forms. Rather he felt that Boyle really wanted to explain the nature of nitre and its heterogeneous body whereas he did not necessarily achieve this. He went on to say that it was not necessary to prove his own suppositions – that he had merely to suppose them as an alternative. He reiterated that his experiment on flammability was only to show what common experience held and that indeed even his own experiments only confirmed reason “to a certain extent” (W.124). He goes on to pose what he considers an important unanswered question related to the experiment: Does it cease to be nitre if the particles are rubbed until their shapes change? (W.127). Spinoza again stresses the superfluity of experimentation: Why would it be clearer or prove more than common experience could? He counters that Boyle’s example of burning wood (which he gave as an example of something more simple) is not conclusive since, Spinoza claims, we know the actual nature of either so what is the difference? How does Boyle know what nature actually contributed in the case of this experiment, although it is claimed that the causes are isolated in the laboratory? He gives a counterexample of a “simple” phenomenon, of dye affecting matter – and claims that there may be imperceptible changes in quality (for example odor) or the example of amber, which cannot be perceived until heat is applied to it: How would we rest assured that indeed we had isolated the barest causes and some imperceptible agent was not the true cause? (W.128-9). He says that rather his own explanation is simpler and better than Boyle’s and that his own experiments confirm his hypothesis “to some extent” (Savan 1986, p. 115). Boyle declined to give an exact mechanical commentary and maintained that he had only showed that nitre had been broken up and built up, thus ridding the reliance upon substantial forms, which Spinoza took for granted (Chalmers 2009, p. 109).
In Letter XVI Oldenberg requests Spinoza to please read the preface of the work and to understand the intent was never to explain nature, rather make recordings of a “certain heterogeneity” observed in the experiment. After a few more replies and minor considerations, the exchange was at an end, Boyle remaining silent on many of Spinoza’s exacting insistences (W.136-7).
In analyzing the exchange, Wolf mentions in his introduction that: Spinoza…was a philosopher first and foremost. He was certainly interested also in science […] But his interests were mainly directed to the wider issues involved – issues for which Boyle had little understanding and less appreciation. So the two were not likely to pull well together. Spinoza, indeed, recognized and appreciated the importance of such detailed observations and experiments as Boyle was carrying out and recording. But he also realized their shortcomings, and was candid enough to express his thoughts. (W.42) and states that the “mechanical interpretation of natural phenomena” was the “most important aspect of [the] correspondence” (W.42). Savan points out that Spinoza’s approach was rather “ad hoc” and his experiments were solely conducted as a criticism of Boyle’s work (Savan 1986, p. 95). Gabbey mentions that the further quantitative experiments that Spinoza proposed would also show if fixed nitre was indeed an “impurity” and wondered why he felt his own supposition did not need to be proved as well (Gabbey 1996, p. 178). Gabbey furthermore finds utility in the exchange, urging, “We ought to look afresh at Spinoza’s insistence on the epistemological insufficiencies of the experimental way.” (Gabbey 1996, p. 180). Maull says that Spinoza had “no need to embrace any standard of justification that fell short of deductive proof” (Maull 1986, p. 6) and claims that in posing questions about what experimentation actually yields, the results of both Boyle’s and Spinoza’s experimentations were inconclusive. At any rate, mechanical philosophy was justified by mathematical proofs from “higher principles” which led Descartes himself ultimately to stress that he had only “moral certainty” (ibid). Maull concludes: Spinoza did not consider Boyle’s experiments useless; rather a documentation of every liquid with accuracy; a history or cataloge of nature, but that commonplace observations were equivalent to experimentations, all of which yielded no hypotheses of nature (Maull 1986, p. 7).
As for the philosophical fruits which can be derived from this exchange, I give the following useful point: Which comes first: theory or experimentation? This seems to be the central tension between philosophy and science, one which was well-exemplified in the exchange between Boyle and Spinoza (among countless others). The record of interplay between the two throughout history seems to indicate a cyclic quality which itself continually furthers the progress of both fields. Spinoza and Boyle both claimed that the highest causes were unknowable (although Spinoza, being mainly a philosopher, had more adeptness in sticking to this than did Boyle, immured in the practical field of science). Yet, it is impossible to have only theory, because what we are trying to discover the truth of (ie the universe) is something unknowable without some experience (for example, it is not a logical truth that things made of glass break when dropped upon a hard surface but simply a truth within a system). Contrariwise, experimentation without theory, as Bacon himself posited, is useless and is akin to random scribblings in the dark. Our actions, whether right or wrong, must be guided by theory. Yet, these theories are suppositions of “truth” or “causes”, the very thing which both Spinoza and Boyle (among countless others) acknowledge in the end. I propose that this is a necessary and useful tension. I close with a quote from Chalmers that “What was scientific about the scientific revolution, in my view, was the emergence of experimental science as distinct from philosophical theories about the ultimate structure of matter.” (Chalmers 2009, p. 97).
Abbreviations:
E = Spinoza, Benedict de. Improvement of the Understanding, Ethics and Correspondence. Trans. R. H. M. Elwes. London: M. Walter Dunne, 1901.
S = Selected Philosophical Papers of Robert Boyle. Ed. M. A. Stewart. Indianapolis: Hackett Publishing Company, 1991.
W = The Correspondence of Spinoza. Ed. and trans. A. Wolf. New York: The Dial Press.
Bibliography:
Chalmers, Alan. 2009. The Scientist’s Atom and the Philosopher’s Stone: How Science Succeeded and Philosophy Failed to Gain Knowledge of Atoms. Boston Studies in the Philosophy of Science #279. Berlin: Springer.
Gabbey, Alan. 1996. “Spinoza’s Natural Science and Methodology.” In Garrett 1996, pp. 142-191.
Garber, Daniel. 1988. “New Doctrines of Body and its Powers, Place, and Space.” In Garber , vol. 1, pp. 553-623.
Garber, Daniel, ed. 1988. The Cambridge History of Seventeenth-Century Philosophy: Two Volumes. New York: Cambridge University Press.
Garrett, Don, ed. 1996. The Cambridge Companion to Spinoza. New York: Cambridge University Press.
Grene, Marjorie, and Debra Nails, eds. 1986. Spinoza and the Sciences. Boston Studies in the Philosophy of Science Vol. 91. Dordrecht: D. Reidel Publishing Co.
Maull, Nancy. “Spinoza in the Century of Science.” In Grene, pp. 3-13.
Savan, David. “Spinoza: Scientist and Theorist of Scientific Method.” In Grene, pp. 95- 123.
[1] See Garber 1988, p. 553 for a general overview of the emerging mechanist philosophy, and pages 585 and 588 to see overviews of Descartes’s views as well as a note on the corpuscular philosophy.
[2] See the same citation for Wolf’s assertions as to the plausible cause of why a more direct correspondence was avoided.
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