Francis Bacon’s typology of pneumatic substances

For Bacon, spirit in general is a “breath compounded of an airy and a flamy substance” (OFB VI 321). One extreme is that of the air (rather cold and inactive), the other that of fire. But the mixture of air and fire is not mechanical (OFB XII 355); it is a complete mixture (which cannot be simply evaluated in terms of more air/less fire; or more fire/less air, but has a ‘mysterious’ character, OFB XII 352, 376 etc.). In between ‘air’ and ‘fire,’ we have a whole range of spirits: the non-living ones “are nearly consubstantial to air,” while the “vital spirits come closer to the substance of fire.”(OFB XII 354-5) One fundamental principle in Bacon’ natural philosophy is that there is no tangible body devoid of spirit. By contrast, spirits can be ‘free’ or ‘enclosed’ in matter. Meanwhile, spirits also come in all sorts of shapes and forms: and although Bacon sometimes attempted classifications of pneumaticals (i.e. according to their rarity in HDR) it is clear that their diversity resist any form of unique classification.

In the late natural histories, one can find series of experiments which seem to attempt to classify pneumaticals according to their properties. In some cases, the classification takes into consideration observational properties of pneumatics (hence, the resulting ‘classification’ will be called ‘phenomenological’). In some other cases, (esp. Sylva) the principle of classification seem to be the prevailing process (i.e. physical classifications). There is arguably also an attempt to divide spirits and matter in metaphysical terms.

It is not only that these classifications are not unique, they are also overlapping. However, the recurrence of such attempts to classify spirits in the late natural history seem to signify that Bacon was persuaded of the importance of achieving some form of classification, or typology of pneumatic substance.

Meanwhile, Sylva constantly insists on the diversity of spirits and the diversity of properties characterizing spirits. Spirits are “nothing else but a natural body, rarefied to a proportion, and included in tangible parts of bodies;” in addition, they are many differences between spirits: “they be no less differing one from the other than the dense or tangible parts.”(SEH II 381)

Phenomenological classifications

  1. Classification of spirits according to their rarity (HDR)
  2. Classification of spirits according to their heat (sources of heat, how the heat is processed…) (OFB XII 359)

Close distillation (forcing matter/spirit to react to heat in a close container) (SS I 99), and other experiments with closed containers destined to mix air and flame or watery and oily

  1. Classification of spirits according to the qualities of the mixture of air and flamy (which gives it empirical characteristics such as “greediness,” “lassitude” …).

Physical classifications

  1. Classification according to the organization of spirit in matter (branched, cells, cut-off)
  2. Classification according to the even/uneven distribution of spirit in matter and the fineness of the spirit AND/OR strenght[1]
  3. Classification according to the processes that gets activated

Spirits are said to be the causes of all processes (SS I 98) (but whether a process or another takes over is also a property of spiritual substance?)

Classification in terms of activity (resulting from the activated appetites)

[1] Spirits “weak” “clinging loosely, … practically consubstantial with plain air,” “dwelling mainly the outer parts of the body.;” “transient guests” in bodies – Versus spirits “stronger,” “further inside,” “submerged and buried deeper in the solid parts of the thin.” (OFB VI 291) Also, there is a rule in HVM which links the even/non-even distribution of the spirit with its properties/activity – abundance of spirit non-evenly distributed makes the spirit more predatory OFB XII 361.

Metaphysical classification (?)

Spiritus vitalis/Spiritus mortualis (HVM, OFB XII 351)

(Also: (DVM OFB VI 352-3) – vital spirit, peculiar to living things OFB VI 357 – differs from the other spirits not only because it is differently organized, but because it has an inner warmth and because it feeds upon “the moist parts and joice of the living body” (OFB VI 359))

HVM: Rule/Canon IV: In all living things there are two kinds of spirits: non-living ones (Mortuales) of the kind found in inanimate substances, and the superadded vital spirits.

Vital spirit is something different from all the spirits that exist in inanimate bodies because: it needs aliment, it is somehow closely connected with the body (being ‘in charge’ of the body and all the other spirits), it ‘rules’ the other spirits and the body.

Thus we should know that there exist in flesh, bones, membranes, organs, and every single part of the human body, spirits which pervade them while they live, and which are identical to those which exist in those parts – flesh, bone, membrane and the rest – when they are separate and dead, and identical to the ones remaining in the corpse. But the vital spirit, though it rules and has some consent with them, is very different from them, as it is integral and self-consistent [integralis, & per se Constans]. Now the non-living and vital spirits differ in two main ways: the first is that the non-living spirits are not in the least self-continuous, but are as it were cut off and surrounded by the grosser body which intercepts them rather as air is intermixed in snow or froth. But all vital spirit is self-continuous through certain channels which it pervade, without being completely intercepted. This spirit too is of two kinds: the one is just branched and runs through little thead-like tubes [Ducturs, & tanquam Lineas]’ the other has in addition a cell [Cellam] so that it is not just self-continous but is also gathered together in some hollow space and, relative to the body, in an appreciable quantity; and in this cell is the source of the rivulets which go their separate ways from there. This cell is mainly in the cerebral ventricles, which in humbler creatures are narrow, such that the spirits seem to be diffused through the whole body rather than concentrated in cells, as we see in snakes, eels, and flies whose individual parts still move after being cut away. (OFB XII 351-353)

Although Bacon attempts to reduce this fundamental difference to physical and phenomenological differences, it is not entirely clear that this is a successful enterprise (or an enterprise that can succeed). In principle, the differences are:

  • Of organization (non-living spirits are cut off and not organized) and distribution (within the body; how well distributed are the vein, how far away from the cells etc. see DVM)
  • Of composition (all spirits are a mixture of air and flame, and the living one are closer to the nature of flame, but Bacon emphasizes that this is not a mechanical mixture and hence “when this rule states that vital spirits come closed to the substance of flame, it must be taken to mean that they do so more than the non-living ones, and not that they are more flamy than airy” (OFB XII 355).
  • Of behavior/appetites (the non-living spirits have two appetites/desires – to multiply, and to fly and meet with connaturals; living spirits have more appetites, for example they are “absolutely terrified of leaving its body” – which means that living spirits are “principal” spirits of bodies and they are metaphysically united with their bodies)
  • Of heat/warmth (OFB VI 357)

Another major difference is said that non-living bodies/spirit do not need aliment, while the others do (but, however, spirits in inanimate bodies ‘eat-up’ matter)

DVM: But it is unquestionably the case that among the difference of the spirit there are two in particular which have the greatest importance: for spirits differ in body or in force, for we find that some are more biting, lively and robust while others are duller and weaker. And that very force proceeds either from the nature of the thing, or from the length of time that has elapsed since the death of the body. Alternatively, spirits vary in fraction or comminution, for we find bodies in which the spirtis are more diffused and dispersed so that the portion of spirit in any given part is less than it might be, but other bodies in which the spirts have more space and larger concentrations. But again, we find that the distribution of spirits with reference to their sites is more uniform in certain bodies so that the spirits are diffused more evenly in particular parts of the body; but in other bodies they are distributed less evenly so that the residences of the spirit are more spacious in one place and more confined and circumscribed in another. (OFB VI 282-3)


Hypothesis 1: As with many of his new concepts, Bacon seems to use “spirits” in more than one way; using a range of traditional, loose meanings (spirits are the breath of life, they are the source of activity in the Universe and they originate “in the stars,” there are living spirits and non-living spirits etc.) and a more specific, technical meaning (a class of material substances characterized by rarity, heat (potential or actual heat), active powers, the capacity to diffuse at considerable distances, and other several properties such as greed which Bacon attempts to express in terms of combinations of attributes).

Hypothesis 2: There are small but significant differences between DVM and HVM on the one side and SS on the other regarding the fundamental and derivative properties of pneumaticals. These differences can originate in the fact that in SS Bacon asks different questions and is interested in different aspects of the workings of spirits than in the other two works. Thus, there is no equivalent of spiritus mortualis at work. Meanwhile, there seem to be a distinction between the principal spirit of a body and other spirits which might (or might not) inhabit the same body. The principal spirit can be the living spirit of DVM and HDR. Meanwhile, there clearly are other organized spirits at work in the same body (a scion grafted on a stock poses this problem of two principal spirits ‘fighting’ and one is overcoming the other).

Sylva Sylvarum has a number of experiments which seem to be saying that there is no metaphysical distinction between vital spirits and the others, that there is indeed a merely variation in the mixture of air and flame at work, and that one can simply vary the proportion of the two in the mixture

SS1.30 “although air and flame being free will not well mingle; yet bout in by a body that hath some fixing, they will. For that you may best see in those two bodies (which are their aliments) water and oil; for they likewise will not well mingle of themselves, but in the bodies of plants and living creatures they will.”

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).

Glossary: Spirits


Spirit(s) is one of the most important Baconian terms, featuring prominently in all his works. In the natural historical works (see below) the term is strongly linked/intertwined with Bacon’s ‘pneumatical’ (i.e. ‘spiritual’) matter theory.

Works: Sylva sylvarum (SEH II)

Historia vitae et mortis (OFB XII)

Historia densi et rari (OFB XIII)

De vijs mortis (OFB VI)

For Bacon there are two kinds of matter: tangible and pneumatic. The pneumatic one is also called “spirit” and it is present in every tangible body, being the cause of all actions and visible processes that we observe in the natural world. If the tangible matter is inert, the spirit is very active. In SS experiment 98, Bacon offers a definition of the spirit: “For spirits are nothing else but a natural body, rarefied to a proportion, and included in the tangible parts of bodies, as in an integument. And they be no less differing one from the other than the dense or tangible parts; and they are in all tangible bodies whatsoever, more or less; and they are never (almost) at rest; and from them and their motions principally proceed arefaction, colliquation, concoction, maturation, putrefaction, vivification, and most of the effects of nature.” A similar definition is to be found in HVM: “a body thin and invisible, yet something real with place and extension” (OFB XII, 347-49). it is an important feature in Baconian philosophy that in order to perform changes upon nature, the philosopher has to manipulate the spirits, and this is done through governing their appetites.

There are two main kinds of spirits: non-living (‘mortuales’) and vital (‘vitalis’), the first in inanimate beings and the second in animate ones. There are two main differences between them: spirits of things animate are all continued with themselves, and are branched in veins and secret canals and “the spirits of animate bodies are all in some degree (more or less) kindled and inflamed, and have a fine commixture of flame, and an aerial substance. But inanimate bodies have their spirits no whit inflamed or kindled” (SS, exp. 601). As a consequence of these differences, Bacon finds seven differences between plants and inanimate bodies: firstly, plants are determinate and figurate by the spirit, secondly, pants do nourish, while inanimate bodies do not. Thirdly, plants have a period of life, inanimate bodies not. Fourthly, they have a succession and propagation of their kind, while inanimates do not have it. The last three differences are: metals are more durable than plants, they are more solid and hard and lastly, they are holly subterranean (SS, exp. 601-606).

Within the animate bodies, there are again two types of spirits: those of plants and those of living creatures (animals). Again there are two main differences between them. Firstly, in living creatures the spirits have a cell, while in plants they are organized in branches; and secondly, the spirits of living creatures have more flame and less air, while the spirits of plants are more airy and less flamy, even though, being pneumatic, both are airy and flamy to some degree. But there are also eight secondary differences as a consequence of the two primary ones: a)  plants are fixed to the earth, while living creature are severed; b) living creatures have local motion, while plants do not; c) living creatures nourish themselves from their upper part, plants from below; d) plants have their seed and seminal parts uppermost, while living creatures have them lowermost; e) living creature have a more exact figure than plants; f) living creatures have a greater diversity of organs and inward figures than plants; g) living creatures have sense, plants do not; h) living creatures have voluntary motion, while plants do not. In animate bodies, there are also inanimate spirits, in a constant struggle with the tangible matter and with the other pneumatics. These non-living spirits are responsible for the consumption of bodies and the death of things, while the animates are responsible for the process of nourishment of the body where they live (SS, exp. 607-612 and HVM, OFB XII, p. 351).

The non-living spirits contained in the body want to get out and unite with the air, given their airy nature. This appetite has five consequences: if the spirit is detained in the body, but moves violently there follows colliquation (as in metals), if it moves mildly, it follows maturation and digestion (fruits and liquors), if the spirits protrude a little and the movement is confused, putrefaction follows (as in rotten fruits, flesh, shinning wood), if the motion is ordered, then vivification and figuration follows (as in the creatures bred of putrefaction and those perfect); and if the spirits leave the body there follows desiccation, induration, consumption (as in bricks or in the evaporation of liquids) (SS, introduction to exp. 329).

Sulphur quaternion


Mercury quaternion

Tangibles bodies (with attached   spirits)



Salts (subterranean and in organic   beings)



Oil and oily inflammable substances


Juices of animals and plants

Water and crude non-inflammable   substances


Pneumatic substances

Terrestrial fire


‘Attached’ animate and inanimate   spirits

(in tangible bodies)



Sidereal fire

(planetary matter)

Heaven of the fixed stars


(planetary medium)

Graham Rees, The structure of Bacon’s matter theory,  “Matter Theory: A Unifying factor in Bacon’s Natural Philosophy,” Ambix, 25 (1977), p. 117.