On the Soul

1. Introduction

On the Soul (De Anima) is Aristotle’s principal work on psychology and the philosophy of mind. It investigates what it is to be alive and what distinguishes living beings—plants, animals, and humans—from inanimate bodies. Rather than treating the soul as a ghostly substance, Aristotle analyzes it as the organizing principle of a living body, responsible for nutrition, perception, movement, and thought.

The treatise is positioned at the intersection of Aristotle’s biology, metaphysics, and epistemology. It presupposes his general theory of substances as composites of matter and form and applies this framework to living beings. In doing so, it offers one of the earliest systematic accounts of:

• Levels of life, from basic growth and reproduction to sense-perception and rational thought.
• Perceptual processes, including how the sense-organs are affected by their objects.
• Imagination (phantasia) and its role in action and cognition.
• Intellect (nous), including the controversial distinction between active and passive intellect.

Because of its compact and programmatic character, De Anima became a focal point for later interpretive traditions. Ancient, medieval, and modern commentators have treated it as a key to Aristotle’s understanding of consciousness, intentionality, and embodiment, while disagreeing sharply about its more cryptic passages, especially those on intellect.

Within Aristotle’s corpus, On the Soul functions as a theoretical center for a broader cluster of works on psychological and biological topics (often grouped as the Parva Naturalia), in which he explores particular capacities such as memory, sleep, and sensation in greater detail. The treatise itself, however, remains concerned with the general nature and powers of the soul, and with the conceptual tools needed to study them as natural phenomena.

2. Historical and Intellectual Context

2.1 Greek Theories of Soul Before Aristotle

De Anima engages an already rich spectrum of Greek views:

Aristotle reviews these positions in Book I, often by name, and uses them as foils for his own account.

2.2 Intellectual Setting in the 4th Century BCE

The treatise reflects debates in late Classical Athens about:

• The status of the soul: whether it is material, immaterial, mortal, or immortal.
• The sources of cognition: innate knowledge vs. learning from perception.
• The relation between physics and psychology: whether psychological explanations can be reduced to bodily processes.

Plato’s dialogues—especially Phaedo, Republic, Phaedrus, and Timaeus—had recently given influential arguments for the soul’s immortality and tripartite structure. At the same time, natural philosophers and physicians emphasized physiological mechanisms. De Anima situates itself between these extremes by integrating the explanatory ambitions of natural science with a critical appropriation of Platonic themes.

2.3 Place within Aristotle’s Own System

Within Aristotle’s broader philosophy:

• The treatise presupposes his hylomorphic metaphysics (matter–form composition).
• It interacts with his biological works, which provide empirical material on organisms.
• It prepares for ethical and political writings by analyzing the psychological basis of action, desire, and deliberation.

Commentators often emphasize that On the Soul aims to be a scientific account in Aristotle’s sense: an explanation of phenomena (perception, thought, motion) through their causes, grounded in a general theory of living substance.

3. Author and Composition

3.1 Aristotle as Author

Ancient and modern scholarship uniformly attribute De Anima to Aristotle of Stagira (384–322 BCE). The style, vocabulary, and cross-references to other Aristotelian works are widely regarded as authentic, and no serious rival attribution has been proposed.

3.2 Date of Composition

Most scholars date the work to Aristotle’s middle period, during his teaching at the Lyceum in Athens, roughly 350–340 BCE. This dating is inferred from:

• Doctrinal continuity with biological works thought to be from the same phase.
• Mature use of the matter–form framework, but prior to some later refinements.
• Stylistic features similar to other so‑called “esoteric” treatises.

Some interpreters allow for light revision over time but see no strong evidence of radical reworking.

3.3 Intended Audience and Genre

De Anima appears to be a school treatise or reworked lecture notes rather than a polished dialogue. Its compressed style, technical terminology, and programmatic remarks suggest an audience of advanced students in the Lyceum, familiar with Aristotle’s logical and metaphysical doctrines.

The work belongs to Aristotle’s scientific writings (apodeiktika), aiming at explanatory accounts rather than rhetorical persuasion. It serves as a high-level framework for more specialized investigations of psychological functions in related treatises.

3.4 Relation to Other Aristotelian Texts

Within Aristotle’s oeuvre, On the Soul is closely connected to:

Some scholars propose that Aristotle composed De Anima partly to systematize and integrate psychological assumptions already operative in his biological and ethical research.

4. Textual History and Manuscript Tradition

4.1 Ancient Transmission

No autograph of De Anima survives. Ancient evidence suggests the text originated as internal teaching material at the Lyceum. It likely circulated in the Peripatetic school, was incorporated into the collection of Aristotle’s writings associated with Andronicus of Rhodes in the 1st century BCE, and from then on formed part of the standard Aristotelian corpus.

Direct references in late Hellenistic and early Imperial authors are sparse, but by the time of Alexander of Aphrodisias (late 2nd–early 3rd century CE), the treatise was firmly canonized and attracted detailed commentary.

4.2 Greek Manuscript Tradition

The extant Greek text is preserved through medieval copies:

Critical editions reconstruct the text by comparing this manuscript tradition, supplemented by indirect evidence from ancient commentaries and early translations.

4.3 Ancient Translations and Versions

Early translations facilitated the spread and interpretation of De Anima:

These versions sometimes preserve readings that diverge from the medieval Greek manuscripts, contributing to modern textual criticism.

4.4 Modern Editions

Modern critical editions typically follow Bekker’s Aristotelis Opera (1831) as a base, refined by later philologists. The most widely used scholarly texts appear in the Oxford Classical Texts and subsequent editions. Although the text is generally considered stable, certain passages—especially those on intellect—remain textually and interpretively contested, with editors differing over punctuation, word choice, and the status of possible glosses.

5. Structure and Organization of De Anima

The work is divided into three books, each with a distinct but interconnected task.

5.1 Book I: Critical and Methodological Prologue

Book I surveys previous theories of the soul and sets the conditions for a satisfactory account. Aristotle:

• Reviews Presocratic, Platonic, and medical views.
• Criticizes reductions of soul to a material element or to mere motion.
• Emphasizes that the soul must be studied as the principle of living bodies, using the same analytical tools applied to natural substances.

This book is predominantly preparatory, clearing conceptual ground and articulating methodological constraints.

5.2 Book II: Definition and General Powers of the Soul

Book II offers the core definition of soul and outlines its main faculties:

• Presents the hylomorphic definition: the soul as the “first actuality” of a natural organized body potentially alive.
• Analyzes the lowest-level capacities—nutrition, growth, and reproduction—as common to all living things.
• Introduces the higher faculties: perception, desire, and locomotion, indicating how they build upon the nutritive level.

The discussion alternates between general characterization and targeted treatment of specific powers, especially the framework for sense-perception.

5.3 Book III: Higher Faculties and Integration

Book III deepens the analysis of selected capacities:

• Clarifies aspects of perception and introduces the common sense.
• Develops a distinctive account of imagination (phantasia).
• Treats intellect (nous), including the active–passive distinction.
• Explores desire and animal self-movement, and reflects on the unity of the soul’s powers.

The organization is thematic rather than strictly linear; some chapters revisit earlier topics from a more advanced standpoint. Many commentators view Books II and III together as the substantive psychological doctrine, with Book I as their methodological preface.

6. The Hylomorphic Definition of the Soul

6.1 Core Formulation

In Book II Aristotle famously defines the soul as:

"

“the first actuality of a natural body having life potentially in it.”

— Aristotle, De Anima 412a27–28

This formulation employs his general hylomorphic scheme, according to which substances are composites of matter (the underlying stuff) and form (the organizing principle). The soul is identified with the form or organizing actuality of a living body, not with a separate substance inhabiting it.

6.2 First Actuality and Second Actuality

Aristotle distinguishes:

The soul is a first actuality: it is the possession of capacities that make a body a living organism, even when those capacities are not in use.

6.3 Avoiding Dualism and Reductionism

Aristotle’s definition positions the soul:

• Against Platonic dualism, which treats soul as a separable, self-subsistent entity: on his view, most soul-functions depend inherently on an appropriate body.
• Against reductive materialism, which would identify the soul with a specific kind of matter: he insists that explanation must appeal to form, structure, and function, not only to material composition.

Some interpreters emphasize the functional character of this account, seeing the soul as the set of capacities and operations that define a living system. Others stress its metaphysical aspect: the soul as substantial form, grounding the being and identity of the organism.

6.4 Species-Specific Souls

Aristotle treats soul as a general kind realized differently in various species:

• Plants possess only the nutritive soul.
• Non-human animals have nutritive and perceptive (often also locomotive) powers.
• Humans uniquely add intellect while encompassing all lower powers.

This layered conception allows Aristotle to explain differences among living beings by reference to the different complexes of form (soul) instantiated in suitably organized bodies.

7. Faculties of the Soul: Nutrition, Perception, and Desire

7.1 Hierarchy of Faculties

Aristotle organizes soul-powers into a hierarchy, where higher faculties presuppose the lower:

Locomotion and intellect are treated elsewhere, but they build upon these basic faculties.

7.2 Nutritive Soul

The nutritive faculty accounts for:

• Taking in and assimilating food.
• Growth and maintenance of bodily structure.
• Reproduction as a way of “participating in the eternal and divine.”

Aristotle attributes this power even to plants. It operates without perception or awareness and is considered the minimal condition for being alive.

7.3 Perceptive Soul

The perceptive faculty adds:

• Reception of sensible forms through the sense-organs.
• Awareness of environmental features relevant to survival, such as food and danger.

Aristotle holds that all animals have at least touch, and many have additional senses. Perception is described as the organ becoming like its object “in form,” a topic further elaborated in discussions of form without matter.

7.4 Desire (Orexis)

Desire is introduced as a generic power covering:

• Epithymia (appetite) for pleasure, often linked to bodily needs.
• Thymos (spirit) associated with anger and assertiveness.
• Boulēsis (wish) for what appears good under rational consideration.

Aristotle argues that wherever there is perception or imagination, there is some form of desire. Desire functions as a bridge between cognition and motion, since it orients organisms toward or away from perceived or imagined objects. Human desire includes a rational dimension, but the basic structure—an inclination toward the apparent good—is shared with non-rational animals.

8. Perception, Common Sense, and Form Without Matter

8.1 Perception as Reception of Form

Aristotle characterizes sense-perception as the reception of form without matter:

"

“Perception is receptive of the sensible forms without the matter.”

— Aristotle, De Anima 424a17–18

In this account, a sense-organ is potentially like the sensible quality (e.g., color, sound). When stimulated, it becomes actually like it in respect of form, without becoming the material object itself. This allows Aristotle to explain intentionality—being about something—without positing internal copies of matter.

8.2 Individual Senses

He analyzes the five standard senses—sight, hearing, smell, taste, touch—in terms of:

• A specific medium (air, water, transparent) where applicable.
• A proper sensible (e.g., color for sight, sound for hearing).
• A sense-organ structurally adapted to its domain.

Different sensory modalities share the general structure of passive potentiality actualized by the presence of an appropriate sensible object.

8.3 Common Sense (Koinē Aisthēsis)

Aristotle posits a common sense to explain phenomena that single senses cannot account for:

• Perceiving common sensibles such as motion, number, and shape.
• Coordinating information from different senses (e.g., judging that the white and the sweet belong to the same object).
• Being aware that one is perceiving.

The common sense is not treated as a separate organ but as a higher-order capacity that unifies and monitors the operations of the individual senses. Interpretations differ on whether Aristotle locates it in a specific bodily part (often associated in later tradition with the heart) or treats it more functionally.

8.4 Interpretive Debates

Commentators offer various reconstructions:

These debates shape contemporary uses of Aristotle’s theory in discussions of perception and consciousness.

9. Imagination (Phantasia) and its Role

9.1 Distinguishing Imagination

In Book III Aristotle introduces phantasia as a faculty distinct from both perception and thought:

"

“Imagination is that in virtue of which an image (phantasma) occurs in us.”

— Aristotle, De Anima 428a1–2

He argues that imagination cannot be reduced to:

• Perception, since it can occur without present objects (e.g., dreams).
• Opinion or belief, since one can recognize an image as merely imagined without assenting to its truth.

9.2 Types and Conditions of Imagination

Aristotle discusses several forms of imagination:

• Perceptual imagination, closely tied to current sensory input.
• Retentive imagination, preserving images for later use (memory-related).
• Deliberative imagination, employed by rational agents in considering possible courses of action.

Imagination depends causally on perception—no imagining without prior sensing—but can operate in its absence, as in dreams and hallucinations. It is characterized as a kind of movement in the soul produced by actual perception.

9.3 Role in Animal and Human Life

Imagination plays multiple roles:

• In animals, it guides movement by presenting objects as to-be-pursued or avoided when direct perception is absent or partial.
• In humans, it mediates between perception and intellect: intellectual thought is often said to require images (phantasmata) as its basis or accompaniment.

This gives imagination a central position in explaining action, practical reasoning, and even theoretical cognition.

9.4 Interpretive Perspectives

Scholars diverge on:

These differing readings influence how De Anima is used in modern theories of mental imagery, representation, and practical deliberation.

10. Intellect, Active and Passive Nous

10.1 General Characterization of Intellect

In Book III Aristotle turns to intellect (nous) as the capacity for thinking universals and non-sensible objects. He emphasizes:

• Intellect’s receptivity to forms: it becomes what it thinks, analogously to perception.
• Its need to be unmixed and not tied to any particular bodily qualities, in order to receive all forms.

This distinguishes intellect from the bodily sense-faculties, even while Aristotle seeks analogies with perception.

10.2 Passive Intellect (Nous Pathetikos)

Aristotle describes a “passive” or “patient” intellect:

"

“Intellect which is in a way passive is corruptible, and without it nothing thinks.”

— Aristotle, De Anima 429b30–31

This aspect is:

• Potentially all intelligible forms.
• Actualized when it receives forms made intelligible.
• Said to be perishable or corruptible, leading many to associate it with individual human cognition tied to bodily conditions.

10.3 Active Intellect (Nous Poiētikos)

The treatise then introduces a “productive” or active intellect:

"

“There is also an intellect which is of such a nature as to become all things, and another such as to make all things… this intellect is separate, unmixed, and impassible… and this alone is immortal and eternal.”

— Aristotle, De Anima 430a10–17

Key features attributed to active intellect include:

• Making potential intelligibles actual, analogous to light making colors visible.
• Being “separate” and “unmixed,” suggesting a kind of independence from bodily organs.
• Being “immortal and eternal,” in contrast to the passible intellect.

10.4 Major Interpretive Traditions

Aristotle’s terse remarks have generated extensive debate. Major lines of interpretation include:

There is likewise disagreement over whether Aristotle ultimately affirms individual intellectual immortality, leaves the question open, or restricts immortality to a non-personal intellectual principle.

11. Desire, Locomotion, and Animal Self-Movement

11.1 Desire as a Motive Principle

In analyzing animal movement, Aristotle identifies desire (orexis) as the proximate cause:

"

“It is evident that what originates movement is the object of desire or of thought that is for the sake of something.”

— Aristotle, De Anima 433a9–10

Desire encompasses appetite, spirit, and rational wish, all of which can initiate motion when directed toward an object presented as good or bad.

11.2 Cognitive Conditions for Movement

Movement requires more than bare desire; it presupposes some cognitive presentation:

• Perception of a present object.
• Or imagination of an absent or future one.
• In humans, often deliberative thought about means to ends.

The psychological structure of action thus integrates cognition and desire: a perceived or imagined good arouses desire, which in turn mobilizes the body.

11.3 The Locomotive Faculty

Aristotle sometimes speaks of a distinct locomotive faculty, but he explains its operation partly in physiological terms (e.g., changes in heat and cold in the body) and partly in psychological terms (desire and reasoning). The faculty is:

• Present in animals capable of self-initiated movement.
• Absent in plants, which lack perception and desire in his sense.

He investigates the bodily mechanisms of movement more extensively in his biological writings, while De Anima provides the higher-level psychological account.

11.4 Interpretive Issues

Commentators discuss several questions:

These debates influence how De Anima is read in relation to Aristotle’s ethics (where desire and choice are central) and his biology (where movement is studied materially).

12. Philosophical Method and Scientific Aims

12.1 Starting from Appearances

Aristotle repeatedly insists that the study of soul must begin from endoxa—reputable opinions and observable phenomena:

• He collects puzzles and conflicting views about soul.
• He seeks an account that preserves what is compelling in these views while resolving contradictions.

This dialectical starting point is characteristic of his broader philosophical method.

12.2 Soul as Object of Natural Science

In De Anima, psychology is framed as part of natural philosophy:

"

“The inquiry into soul belongs to the natural philosopher.”

— Aristotle, De Anima 403a25–26

The soul is treated as the form of a natural body, and its study is coordinated with investigation of living organisms. Aristotle thus aims at scientific explanations (aitiai) of psychological phenomena, identifying their formal, material, efficient, and final causes.

12.3 Use of Conceptual Tools

The treatise makes systematic use of:

• Potentiality and actuality to explain capacities and their exercise.
• Matter and form to relate psychological functions to bodily structures.
• Teleology to understand faculties in terms of their characteristic ends (e.g., survival, reproduction, knowledge).

These tools allow him to integrate psychological explanations into his general metaphysics without reducing them to merely mechanical processes.

12.4 Programmatic and Schematic Character

Many passages in De Anima are intentionally schematic, laying out problems and conceptual frameworks rather than fully detailed empirical theories. Aristotle often gestures toward further investigation in biological treatises or in the Parva Naturalia. Modern scholars differ on how complete he intended the work to be:

These methodological features have made the treatise particularly adaptable to later traditions that seek either to systematize or to extend Aristotle’s psychology.

13. Famous Passages and Key Doctrinal Cruxes

13.1 Definition of the Soul (II.1)

The passage at 412a27–412b5 contains the classic hylomorphic definition:

"

“The soul is the first actuality of a natural body having life potentially in it.”

— Aristotle, De Anima 412a27–28

Debates center on how to interpret “first actuality” and the implications for the soul’s dependence on the body.

13.2 Eye and Sight Analogy (II.1)

Aristotle likens the relation of soul to body to that of sight to the eye:

"

“If an eye were an animal, sight would be its soul.”

— Aristotle, De Anima 412b18–19

This analogy is widely cited to illustrate his anti-dualist stance and to clarify how form relates to an organ.

13.3 Perception as Form Without Matter (II.12; III.2)

The brief claim at 424a17–21, together with discussions at 416b–418a and 424a–425b, has become foundational for theories of intentionality:

"

“Perception is receptive of the sensible forms without the matter.”

— Aristotle, De Anima 424a17–18

Controversies include the ontological status of these “forms” and the degree of physiological change involved.

13.4 Programmatic Account of Imagination (III.3)

In 427b14–429a9, Aristotle’s delineation of phantasia raises questions about its exact nature and scope. The text’s concise and sometimes elusive formulations have led to divergent accounts of whether imagination is sensory, cognitive, or both.

13.5 Active and Passive Intellect (III.5)

Perhaps the most debated passage is 429a10–430a26, where Aristotle sketches his doctrine of active and passive intellect. Phrases such as “separate,” “unmixed,” and “immortal and eternal” have fueled competing interpretations regarding:

• The individuality vs. universality of intellect.
• The possibility of personal immortality.
• The relation between human and divine thinking.

13.6 Unity of the Soul’s Powers (III.9–13)

Aristotle’s reflections on how multiple faculties belong to a single soul, especially in connection with desire and movement, raise issues about psychological unity and the structure of explanation. Commentators debate whether his account yields a tightly integrated system or a looser aggregation of powers.

14. Medieval and Early Modern Interpretations

14.1 Late Antique and Islamic Commentators

Late antique Greek commentators such as Alexander of Aphrodisias, Themistius, and Philoponus established influential readings, especially of intellect. Their work, translated into Syriac and Arabic, shaped Islamic philosophy:

Islamic thinkers developed systematic psychologies based on De Anima, often linking Aristotle’s account to theories of prophecy, divine intellect, and spiritual ascent.

14.2 Latin Scholasticism

Latin translations from the 12th century onward made De Anima central to university curricula. Key scholastic interpreters include:

• Albert the Great and Thomas Aquinas, who integrated Aristotle with Christian doctrine, typically treating the human soul as the substantial form of the body and arguing for individual immortality.
• Duns Scotus and Ockham, who raised questions about the nature of universals, cognition, and the soul–body relation.

Debates over active intellect generated distinct schools:

Ecclesiastical authorities sometimes condemned Averroist theses as incompatible with Christian doctrine.

14.3 Early Modern Engagements

Early modern philosophers encountered Aristotle largely through scholastic interpretations, but many also read De Anima directly:

• Descartes rejected Aristotelian hylomorphism in favor of mind–body dualism, while still grappling with Aristotelian psychology in his critique.
• Hobbes and later materialists criticized the notion of “soul” as an explanatory principle, favoring mechanical accounts of perception and motion.
• Leibniz and some rationalists retained modified forms of substantial forms and appetitions, drawing selectively on Aristotelian concepts.

Natural philosophers in the 17th century increasingly sidelined De Anima as a scientific authority, yet continued to use it as a reference point in defining new conceptions of mind, consciousness, and mechanism.

15. Contemporary Relevance in Philosophy of Mind

15.1 Embodied and Non-Reductive Approaches

Aristotle’s conception of the soul as the form of a living body has attracted renewed interest among philosophers seeking alternatives to both Cartesian dualism and reductive physicalism. Some contemporary theorists, often labeled “neo‑Aristotelians,” draw on hylomorphism to argue that:

• Mental properties are neither separate substances nor identical with brain states.
• Psychological explanation is irreducibly organizational and teleological, yet fully naturalistic.

Critics question whether such frameworks can be integrated with current neuroscience without reintroducing obscure metaphysical entities.

15.2 Functionalism and Teleology

Aristotle’s analysis of faculties in terms of their characteristic functions invites comparison with modern functionalism:

However, Aristotle grounds functions in natural ends (teleology), whereas many functionalists avoid teleological language or reinterpret it in evolutionary or systemic terms.

15.3 Perception and Intentionality

Discussions of perceptual content and intentionality frequently revisit Aristotle’s idea of receiving “form without matter.” Some interpret this as anticipating representationalism; others view it as offering a relational or direct realist model. Debates focus on:

• Whether perceptual content should be understood as structural similarity, causal power, or something else.
• How to account for error and illusion within an Aristotelian framework.

15.4 Consciousness, Self-Awareness, and Common Sense

Aristotle’s notion of common sense and his remarks about “perceiving that we perceive” are cited in contemporary work on:

• Higher-order theories of consciousness.
• The integration of multisensory information.
• Minimal self-awareness.

Interpretations vary on how close these Aristotelian ideas are to modern notions of phenomenal consciousness.

15.5 Ethics, Action, and Practical Reason

Aristotle’s treatment of desire, imagination, and deliberation in De Anima informs current discussions of:

• The psychology of action and motivation.
• The role of non-conceptual representation in practical reasoning.
• Weakness of will and conflict between rational and non-rational desires.

Philosophers of action and moral psychology often draw on these analyses to refine accounts of rational agency and embodiment.

16. Legacy and Historical Significance

16.1 Central Text in the Aristotelian Tradition

Across antiquity, the Middle Ages, and early modernity, De Anima functioned as the principal entry point into Aristotelian psychology. It shaped:

• Curricula in philosophy and theology.
• Commentarial traditions in Greek, Arabic, Latin, and vernacular languages.
• Systematic treatises on the soul, intellect, and the passions.

Its framework became a shared reference even among thinkers who ultimately rejected or modified Aristotle’s conclusions.

16.2 Influence on Theological and Religious Thought

In Jewish, Christian, and Islamic traditions, On the Soul provided conceptual tools for articulating doctrines of:

• Human nature as a composite of body and soul.
• Intellectual and moral powers.
• Immortality and resurrection.

Different communities adapted Aristotle’s account to their scriptural and doctrinal commitments, generating distinctive syntheses and controversies.

16.3 Impact on Scientific and Philosophical Conceptions of Mind

Although mechanistic science in the 17th century largely displaced Aristotelian natural philosophy, De Anima continued to influence:

• Early physiological and psychological theories, often framed in reaction to its concepts.
• Debates about the legitimacy of teleological explanation in biology and psychology.
• Later movements, including phenomenology and analytic neo‑Aristotelianism, which returned to its notions of embodiment, intentionality, and form.

16.4 Ongoing Scholarly Debates

The treatise remains a focus of active research:

Through these discussions, On the Soul continues to serve both as a historical document and as a resource for rethinking foundational questions about life, mind, and their place in nature.