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.

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