Glossary: Appetite

Works: Abecedarium novum naturae (OFB XIII)

Sylva sylvarum (SEH II)

The term ‘appetite’ is a key concept within Baconian natural and moral philosophy, though Bacon never gives a definition or a clear explanation of the term. What can be understood from the several discussions about the appetites is that they are the causes of all actions in nature, both in the inanimate and in the animate realm, and at the distinct levels, from the last particles of matter to the most complex beings. At a micro level, they are also the causes for the existence of compound bodies. From the Abecedarium novum nature it becomes evident that there are four classes of appetites of bodies: for preserving themselves, for bettering their condition, for multiplying themselves and applying their form, and for imposing themselves upon other bodies (ANN, OFB XIII, p. 197). For each of these appetites there are several correspondent simple motions.

Simple motions and their correspondent appetites (ANN):

Of resistance

Of connection

Of liberty                                            self-preservation

Of self-continuity


Of hyle

Of the mayor congregation

Of the minor congregation                bettering of their condition

Of disposition


Of assimilation

Of excitation

Of impression                                     propagation of their nature

Media of motion


Royal motion

Spontaneous motion

Of repose                                           enjoyment of their nature

Of trepidation

In her book Entre el atomismo y la alquimia, Silvia Manzo defines motion as the effect of an appetite and the appetite itself. There is no difference for Bacon, says her, between the tendency to motion (appetite) and the motion itself. Moreover, she discusses the relation between the appetites of matter and the distinct kinds of good propsed in ethics – comun and private (pp. 69-82), both for inanimate, and for animate matter. Tangible matter has two main appetites, to reject vacuum and to consolidate its proper nature. On the other hand, spiritual matter has three appetites: to enjoy its proper nature, to multiply itself upon other spirits and to escape and unite with their connaturals. The main processes in nature (desiccation, liquefaction, putrefaction, and vivification) are the effect of these appetites and the relation between them (pp. 83-85) and between tangible and pneumatic matter.

Most important experiments in SS in which it is given an explanation based on the appetites of matter are: 24 (appetite of continuation in liquids), 33 (appetite of union of dense bodies), 290 (appetite to receive the sound), 293 (appetite of union in bodies), 300 (appetite of the stomach), 336 (appetite of issuing in spirits), 713 & 714 (appetite to expell what strikes the spirits), 716 (appetite to revenge), 763 (appetite not to move), 800 (appetite of bodies to take in others), 831 (appetite in the stomach), 845 (appetite of not discontinuing), 846 (appetite to conitnuity), 931 (venenous appetite of musk, amber, civet), 944 (appetite of contact and conjunction).

IV. Seventeenth-Century Experiments with Glass Drops: Robert Hooke on glass drops

In the previous posts, I have introduced the problem of glass drops in the seventeenth-century natural philosophy, which I have further discussed in the case of Jacques Rohault’s Cartesian experimentalism and other Cartesian explanations provided by Henricus Regius and Nicolas-Joseph Poisson.

In the final post on this topic, I would like to refer to the explanation provided by an experimental philosopher par excellence, Robert Hooke (1635-1703).

Some of the earliest investigations of the drops took place in the Royal Society (see Brodsley, Laurel, Charles Frank, and John Steeds. 1986. “Prince Rupert’s Drops.” Notes and Records of the Royal Society of London 41 (1) (October): 1–26). Hooke was one of its most distinguished members and witnessed these inquiries from the very beginning (see Birch, Thomas. 1756. History of the Royal Society. Vol. I. London: A. Millar). After an initial report signed by Robert Moray in 1661, Hooke published his own observations in the celebrated Micrographia of 1665. He applies jointly direct observation, hypothetical thinking, and experiment in order to formulate an explanation “Of some Phenomena of Glass drops,” as it is said in the title of his seventh observation. As expected, glass drops and fragments of drops are examined through the microscope. Yet, Hooke notes the difficulties of his inquiry: “I could not find, either with my naked Eye, or a Microscope, that any of the broken pieces were of a regular figure, nor any one like another, but for the most part those that flaw’d off in large pieces were prettily branched” (p. 33). Trying to find the imperfection of glass, sets Hooke on a quest of successive trials, such as grinding the object in different parts and observe if there are new effects or immersing glass drops in various substances (e.g., Icthyocolla). Like in the prior cases of Rohault and Regius, Hooke complements his text with an illustration (see Fig. X at the bottom of this image):

Robert Hooke, Micrographia (1665).

The object is not only investigated empirically with various instruments, but the ‘conjectures’ formed in this process are further examined through analogy and transduction, which ports theoretical elements into Hooke’s analysis. Moreover, descending into the invisible structures of matter, forces him to leave the eye and the microscope and frame his explanation on top of other prior considerations about heat, fluidity, and matter in general. He concludes by ascribing the cause to the arrangement of particles of glass, which are gathered into a springy tension inside the drop.

It is not the place in this blog-post to go into the details of Hooke’s explanation of the phenomena produced by glass drops, but it is worth noticing that his experimental methodology overlaps with what I have presented in the post dedicated to Rohault. Theory and experimentation work together in finding the explanation, which, ultimately reduces to a mechanical model of the accepted theory of matter. These four cases of seventeenth-century natural philosophers interested in the study of glass drops make wonderful examples of how “new scientific objects” are discussed and explored with new methodological tools. I shall investigate this problem into a forthcoming article.

III. Seventeenth-Century Experiments with Glass Drops: Henricus Regius and Nicolas Poisson on glass drops

Rohault was not the only Cartesian natural philosopher interested into the mysteries of glass drops. Others have started to examine the object and to produce their own explanations. In this post, I shall refer to the cases of Henricus Regius and Nicolas Poisson.

Regius (1598-1679) was a former friend of Descartes, who eventually felt into disgrace in the 1640s as a result of the disputes stirred at the University of Utrecht (see Verbeek, Theo. 1988. La Querelle d’Utrecht, Paris: Les impressions nouvelles). Descartes’s accusations from the preface letter to the French edition of the Principia philosophiae (1647) are directed to Regius’s new treatise Fundamenta Physices (1646). The accusations and the dispute between the two are beyond the scope of this post. However, it is important to notice the context in which Regius has developed his natural philosophy. In subsequent editions of the Fundamenta, he explored a larger area of the natural realm, introducing a discussion of glass drops in the final part of the Philosophia naturalis (1661, the third edition of the Fundamenta, but not in the second edition from 1654). This part is an eclectic collection of phenomena, curiosities, and experiments, which is in many ways reminiscent of Francis Bacon’s Sylva sylvarum. And, quite surprisingly, Regius adds his own explanation regarding this new object.

Henricus Regius, Philosophia naturalis (1661), p. 516.

It is evident from the very beginning that he is interested in uncovering the cause and it is not very clear whether he performed any experiments with glass drops. Unlike other explanations, Regius is not very concerned with the structure of the drop in its larger part (the area marked with 1-2 in his illustration), but rather with the structure of the tail. He refers to the structure of the object, which he seeks to explain in terms of glass particles and pores. Even if Regius’s explanation is not very elaborate, it still gives the general outlines found in other popular descriptions of the phenomenon.

Almost a decade later, Nicolas-Joseph Poisson (1637-17010) has published his Commentaire ou remarques sur la méthode de René Descartes (1670). Poisson attempts to defend Descartes’s views on method and he does this by taking each of the four rules expressed in the Discours de la méthode, which are correlated with new experiments and discoveries. In his discussion of the second rule –  “La seconde Regle de la Logique de M. Desc. est de diviser ou faire une espece d’anatomie de la difficulté qu’il se propose d’examiner il la regarde d’abord en general, puis distinguant chaque partie, il les demesle les unes d’avec les autres pour les contempler chacune en particulier, & en connoistre la nature & les proprietez.” (see the 1987 reprint of Poisson’s Commentaire, p. 54) – Poisson introduces the explanation of glass drops. Relying mainly on other testimonies, he is concerned with the explanation of this phenomenon, which he eventually achieves. However, what is peculiar to his explanation is that he begins with a list of what is important in his search. Thus, he enumerates: (1) the material condition (only air and glass are contained in the object); (2) the position of glass; (3) cause of the structure (action of fire); (4) how glass interact; (5) the relation between hot and cold with respect to glass; (6) the existence of a so-called ‘motion of liberty’ of the air that is trapped inside the drops (Poisson refers here to the mechanical tradition); (7) the “elastic” virtue of the air (with reference to Boyle); (8) the heavy force of the trapped air, which he claims will burst with great noise, as soon as it is freed. This list is quite strange, because his explanation can easily be reduced to all these eight points. But this can be due to the interplay between a resolutive and constructive procedure, which is traditionally ascribed to Cartesian method.

These two cases of Cartesian philosophers dealing with a new object puzzling early modern philosophers reveals another layer of the relation between theory and experimentation. Both Regius and Poisson seems to rely on observations and reports produces by others. Experiment is not neglected, yet it is not central, because what both of them seek is to produce an explanation, which ultimately rests on the mechanical structure of invisible parts of matter. In the next post, we shall see how a similar explanation emerges in the case of an experimental philosopher, Robert Hooke.