[2.2.6] Stoic Cosmology

For the Stoics, the universe:

  • is a unitary spherical body located in the void, with properties resembling those of a living being,
  • can be entirely explained by two principles, the active pneuma and the passive matter,
  • has a life cycle consisting of three ever-repeating phases, characterized by the dominance of fire (conflagration), of elements, and of bodies (in the present period).

The stoic cosmological model is using concepts from stoic ontology [2.2.5] and psychology [2.2.1].

The OntoUML diagram below presents the structure of the stoic universe:

Stoic cosmology
Universe“The governing metaphor for Stoic cosmology is biological, in contrast to the fundamentally mechanical conception of the Epicureans. The entire cosmos [universe] is a living thing and God stands to the cosmos as an animal’s life force stands to the animal’s body, enlivening, moving and directing it by its presence throughout. The Stoics insistence that only bodies are capable of causing anything, however, guarantees that this cosmic life force must be conceived of as somehow corporeal.”
“Just as living things have a life-cycle that is witnessed in parents and then again in their off-spring, so too the universe has a life cycle that is repeated. This life cycle is guided by, or equivalent to, a developmental plan that is identified with God. There is a cycle of endless recurrence, beginning from a state in which all is fire, through the generation of the elements, to the creation of the world we are familiar with, and eventually back to the state of pure designing fire called ‘the conflagration’” UniversOnFire,
are all phases of Universe
PneumaGod is identified with an eternal reason or intelligent designing fire or a breath (pneuma) which structures matter in accordance with Its plan. The designing fire is likened to sperm or seed which contains the first principles or directions of all the things which will subsequently develop. The biological conception of God as a kind of living heat or seed from which things grow seems to be fully intended. The further identification of God with pneuma or breath may have its origins in medical theories of the Hellenistic period…
More specifically, God is identical with one of the two ungenerated and indestructible first principles (archai) of the universe.”
is part of the PresentUniverse
Pneuma comes in gradations and endows the bodies which it pervades with different qualities as a result. The pneuma which sustains an inanimate object is a ‘tenor’ (hexis, lit. a holding). Pneuma in plants is, in addition, physique (phusis, lit. ‘nature’). In animals, pneuma is soul (psychê) and in rational animals pneuma is, besides, the [central] commanding faculty (hêgemonikon) – that is responsible for thinking, planning, deciding. The Stoics assign to ‘physique’ or ‘nature’ all the purely physiological life functions of a human animal (such as digestion, breathing, growth etc.) – self-movement from place to place is due to soul. Tenor, Nature, Soul,
CentralCommandingFaculty are subkinds of Pneuma;
Tenor is part of Body;
Nature is part of Plant, Animal and Human;
Soul is part of Animal and Human;
CentralCommandingFaculty is part of Human
Matter “One principle [of the Universe] is matter which they regard as utterly unqualified and inert. It is that which is acted upon.” is contained by the Universe and Body
Body “Only bodies (σώματα, sômata) have being, or exist. Slogan: to exist is to have causal powers. Plato in the Sophist (247d–e): ‘Now, I say that what has some power to make something else into something, or to suffer the slightest, even once, this has real being. For I define being as nothing but power (δύναμις).’ The Stoic conception of existence is thus dynamic. Matter as such is passive, but bodies are not, since they are also infused by logos, which is active… only bodies can act or be acted upon” is part of the PresentUniverse
Inanimate object;
these are BodiesInanimate object,
Plant, Animal,
Human are Body
ElementElements are continuous, infinitely divisible substancesis part of Matter;
is contained by UnverseOfElements
Fire; Earth; Water; AirFire, Earth, Water; Air are elements;
Fire is contained by Universe in Fire


  • All citations from: Baltzly, Dirk, “Stoicism”The Stanford Encyclopedia of Philosophy (Spring 2019 Edition), Edward N. Zalta (ed.)
  • Suzanne Bobizen, Early Stoic Determinism, Presses Universitaires de France | Revue de Métaphysique et de Morale, 2005/4 – n° 48

First published: 28/11/2019

[2.2.4] Ontological Structure of Stoic Logic

Stoic logic, elaborated by Chrysippus (297-206 BC), is one of the two major systems of logic (the other one is Aristotelian logic) in the classical world and can be characterized by:

  • It is propositional logic (unlike the Aristotelian [1.3.9], which is term logic), because analyses the relations and truth values of assertibles (or propositions). Here logical variables are propositions, while in Aristotelian logic terms.
  • It is concerned more with particulars (unlike the Aristotelian logic, which is analyzing categorization and universals) reflecting thus the stoic view that only particulars are real existents (see also [2.2.5]).

The stoic logic, represented in the OntoUML diagram below, operates with the following main classes and relationships:

Stoic logic
SayableSayable (lekta) (see also in [2.2.2]): “are the underlying meanings in everything we say and think, but… also subsist independently of us. They are distinguished from spoken and written linguistic expressions: what we utter are those expressions, but what we say are the sayables.”
AssertibleAssertibles (axiômata) are sayables having a truth value: at any one time they are either true or false. So truth is temporal and assertibles may change their truth-value. They can never be true and false at the same time (law of non-contradiction) and they must be at least true or false (law of excluded middle).is a Sayable
TruthValueTruth value of an Assertible might change over time, so each value is valid from the startTime to endTime.each Assertible has at least 1 truthValue
SimpleAssertibleSimple Assertibles include propositions like: “it is cold”; “it is raining this morning” and “no one is running.” is an Assertible
Non-simpleAssertibleNon-simple Assertibles are compound of simple assertibles linked with logical connectives, like: if.. than, and, either.. or, since, because. E.g. “if it is winter than it is cold”; “either it is day or night”; and “I am moving since I am working”.Non-SimpleAssertible is Assertible; it is a part-hole relationship with the SimpleAssertible
PremisePremise is an Assertible, e.g. “it is winter”; “if it is winter than it is cold”.
ConclusionConclusion is an Assertible, e.g. “it is cold”.
ArgumentArguments relates two (or more) Premises to a Conclusion as cause and effect. At least one Premise has to be a Non-simpleAssertible. E.g.
Premise1: “if it is winter than it is cold”; if P than Q
Premise2: “it is winter”; P
Conclusion: “it is cold”; therefore Q
Argument mediates between Premises and Conclusion
StoicSyllogismStoicSyllogism “is best understood as a… natural-deduction system that consists of five kinds of axiomatic arguments (the indemonstrables) and four inference rules, called themata. An argument is a syllogism precisely if it either is an indemonstrable or can be reduced to one by means of the themata. Thus syllogisms are certain kinds of formally valid arguments. The Stoics explicitly acknowledged that there are valid arguments that are not syllogisms; but assumed that these could be somehow transformed into syllogisms.”if the Argument is valid, it relates to Syllogism;
IndemonstrableThe five indemonstrables are:
1/ Modus ponens: If p, then q.  p. Therefore, q.
2/ Modus tollens: If p, then q. Not q. Therefore, not p.
3/ Not both p and q.  p. Therefore, not q.
4/ Modus tollendo ponens: Either p or q. Not p. Therefore, q.
5/ Modus ponendo tollens: Either p or q.  p. Therefore, not q.
part of StoicSyllogism
ThemataComplex syllogisms could be reduced to the indemonstrables through the use of four ground rules or themata. Of these four, only two have survived.
E.g. when from two assertibles a third follows, then from either of them together with the contradictory of the conclusion the contradictory of the other follows.
part of StoicSyllogism


  • All citations from: Bobzien, Susanne, “Ancient LogicThe Stanford Encyclopedia of Philosophy (Winter 2016 Edition), Edward N. Zalta (ed.)
  • Bobzien, Suzanne, Stoic Logic, Cambridge Companions Online © Cambridge University Press, 2006

First published: 13/06/2019