Monopsychism

Definition and Historical Background

Monopsychism is the doctrine that there is only one intellect or soul shared by all human beings, rather than numerically distinct intellects in each person. In its most influential formulations, monopsychism concerns the intellective soul—the faculty responsible for universal, abstract thought—rather than sensory or vegetative functions.

The term itself is modern, retrospectively applied by historians of philosophy to characterize certain medieval Aristotelian and Averroist positions on the nature of the human intellect. It names a family of views that interpret Aristotle’s account of intellect (nous) as implying that:

• the true subject of thinking is a single, separate intellect, and
• individual humans participate in this intellect through their bodily and imaginative capacities.

While its classical roots lie in the interpretation of Aristotle’s De Anima, monopsychism became a focal point of debate in Islamic philosophy, Latin scholasticism, and later theological controversies, especially surrounding the unity or multiplicity of the human soul and the implications for personal immortality and moral responsibility.

Medieval Aristotelian and Averroist Forms

Medieval monopsychist positions grew out of the difficult passages in De Anima III, where Aristotle distinguishes between:

• the possible (or material) intellect, capable of receiving all forms, and
• the agent (or active) intellect, which “makes all things” intelligible.

Averroes and the single separate intellect

The most famous form is associated with Averroes (Ibn Rushd, 1126–1198). In his Long Commentary on De Anima, Averroes argues that:

• the material intellect is a single, immaterial, separate substance for all humans;
• it is eternal and impassible, not multiplied with individual bodies;
• individual humans contribute phantasms (imaginative images) through their bodily faculties, which the single intellect uses as a basis for universal thought.

On this view, there is one intellect in number (unum intellectum numero) for all human beings. Individual differences in cognition arise from bodily and imaginative conditions, not from distinct intellectual substances. Many medieval Latin readers derived from Averroes the thesis that all humans share one thinking subject, often labeled Averroist monopsychism.

Latin Averroism

In 13th‑century Paris, thinkers such as Siger of Brabant and Boethius of Dacia were accused of holding monopsychist doctrines. Their work attempts to reconcile:

• Aristotelian–Averroist philosophy, which seemed to support a single separate intellect, and
• Christian doctrine, which affirms individual immortal souls and personal responsibility.

Some Latin Averroists proposed a “double truth” interpretation (though often more attributed than embraced): philosophically, reason leads to monopsychism; theologically, faith maintains individual souls. Whether they personally endorsed monopsychism as a final view or as an interpretation of Aristotle remains debated, but their writings gave the doctrine a prominent place in university controversies.

Critiques and Theological Controversies

Monopsychism was forcefully opposed by many scholastic theologians, who regarded it as incompatible with core doctrines concerning the individual person.

Aquinas’s critique

Thomas Aquinas (1225–1274) is the most influential critic. In works such as De unitate intellectus contra Averroistas (“On the Unity of the Intellect Against the Averroists”), he argues that:

• each human has their own subsistent intellectual soul, which is the form of the body;
• thought is an act of the individual person, not of a separate, common substance;
• a numerically single intellect for all is incompatible with:
  • individual knowledge (since the act of understanding would belong to a shared subject),
  • moral responsibility (since blame or praise would fall on the common intellect), and
  • personal immortality (since no individual intellectual substance would remain).

For Aquinas, monopsychism undermines the unity of the human person: if “I” do not strictly think, but only a shared intellect does, then individual human beings become mere instruments or occasions for the act of understanding, not true subjects of intellectual life.

Condemnations and doctrinal stakes

Ecclesiastical authorities explicitly targeted forms of monopsychism. The Condemnation of 1277 in Paris, issued by Bishop Étienne Tempier, anathematized propositions including that there is “only one intellect for all humans.” These condemnations aimed to safeguard:

• the individual soul’s creation and immortality,
• the unity of body and soul in each person, and
• the basis of judgment in an afterlife where individuals, not a shared intellect, are rewarded or punished.

From a theological standpoint, monopsychism raised questions such as:

• How can personal identity survive death if there is only one intellect?
• How can sin and virtue be attributed to individuals if they do not have their own intellectual acts?
• Does a shared intellect reduce humanity to a single spiritual “person” with many bodies?

Opponents therefore often depicted monopsychism as dissolving the distinctiveness of individual persons at the highest level of spiritual life.

Later Developments and Contemporary Resonances

After the medieval period, explicit defense of monopsychism largely disappeared within mainstream Christian and Islamic philosophical traditions, but analogous themes re-emerged in several contexts.

Early modern and idealist parallels

Some historians detect loose affinities between monopsychism and later doctrines such as:

• Spinoza’s view of a single infinite substance with modes of thought and extension, where individual minds are finite modes of one divine intellect;
• certain forms of German Idealism (e.g., in Fichte or Hegel) that emphasize an absolute or world‑spirit within which individual consciousnesses are moments or expressions.

These systems are not straightforwardly monopsychist in the Aristotelian sense, but they similarly explore the idea of a single underlying mind or spirit manifested in many individuals.

Modern philosophical and cognitive discussions

In contemporary discourse, “monopsychism” is mainly a historical label, used in scholarship on:

• Aristotelian psychology and its reception,
• medieval Islamic and Latin philosophy, and
• the development of doctrines of the soul, intellect, and personhood.

More broadly, the term is sometimes invoked, by analogy, in debates on:

• panpsychism or cosmopsychism, where a single cosmic consciousness underlies all minds;
• models of collective cognition or distributed intelligence, though these typically remain metaphorical or functional rather than metaphysical claims about one numerically identical intellect.

In these contemporary settings, “monopsychism” serves less as a live doctrine and more as a conceptual reference point for thinking about the relationship between one mind and many minds, and about how to reconcile shared rationality with individual psychological and moral identity.

Monopsychism thus occupies a distinctive place in the history of philosophy as a carefully articulated attempt—rooted in Aristotelian interpretation—to explain how universal, objective thought might belong, in the most literal sense, to one intellect in which all humans participate. Its critics, emphasizing individuality and personal responsibility, helped shape enduring philosophical accounts of the individual soul and person in Western thought.