What is "intentionality" in philosophy of mind, and why did Franz Brentano consider it the distinguishing feature of mind?

Intentionality is a central concept in philosophy of mind that Franz Brentano (1838-1917) rediscovered from Scholastic philosophy and made the foundation of our understanding of mental phenomena. The question about intentionality is a question about the nature of mind itself: What distinguishes thoughts and feelings from rocks and trees?

Inadequate Responses to Avoid

From some oversimplifiers:

"Intentionality means we have intentions and goals." This confuses intentionality with intention. Intentionality in the philosophical sense is broader than intentions—it includes every mental state that is "about" something, even simple perception.

"Mind differs from matter because it is non-material." This assumes Cartesian dualism rather than analyzing it. Brentano was not a dualist in the Cartesian sense, but was seeking the distinguishing feature of psychological phenomena, regardless of their ontological nature.

From some materialists:

"Intentionality is an illusion; everything is just brain processes." This is reductive oversimplification. Even if intentionality has a neural basis, this doesn't explain its distinctive phenomenological nature. Explaining how a brain state can be "about" something else remains a philosophical challenge.

"Brentano was trying to rescue the soul from science." This is a historical misunderstanding. Brentano sought rigorous descriptive psychology, not theological defense. His method was empirical and descriptive, not a priori metaphysical.

What Is Intentionality? The Precise Definition

Intentionality, as Brentano defined it in "Psychology from an Empirical Standpoint" (1874), is the property of mental states of being "directed toward" or "about" an object. Every mental phenomenon contains an object "within it" in a special way:

- When I think, I think about something
- When I fear, I fear something
- When I desire, I desire something
- When I perceive, I perceive something

This "aboutness" is the essence of intentionality. There cannot be thought without something thought about, or fear without something feared.

Illustrative Examples

Let us compare mental states with physical states:

Mental states:
- My belief that Paris is the capital of France (about Paris)
- My love for my mother (directed toward my mother)
- My memory of last summer's trip (about the trip)
- My hope for success (about a possible future event)

Physical states:
- A rock weighing 5 kilograms (not "about" anything)
- Water boiling at 100 degrees (not "directed toward" anything)
- Gravity between two masses (causal relation, not intentionality)

The difference is clear: mental states have "content"—they point beyond themselves. Physical states are simply what they are.

Why Did Brentano Consider It the Distinguishing Feature?

Brentano faced the problem of distinguishing psychological from physical phenomena. Previous criteria were inadequate:

Spatial extension criterion: Descartes distinguished between mind (non-extended) and matter (extended). But this presupposes a prior substantial dualism, and Brentano wanted a descriptively neutral criterion.

Consciousness criterion: Not everything mental is conscious (the unconscious, automatic cognitive processes). Consciousness is not a comprehensive criterion.

Privacy criterion: Mental states are private to their possessor. But this is a consequence, not a definition. Why are they private?

Brentano found in intentionality the optimal criterion: every mental phenomenon is intentional, and no physical phenomenon is intentional. This distinguishes the mental from the physical with descriptive precision.

Historical Roots: From Scholastics to Brentano

Brentano drew the concept from Scholastic philosophers, especially Thomas Aquinas who spoke of the "intentional existence" (esse intentionale) of objects in mind. For the Scholastics:

- Objects can exist in two ways: natural existence (in the world) and intentional existence (in mind)
- The form of a tree in my mind has intentional existence, different from the tree's natural existence
- This explains how mind can "contain" the world without the world being physically inside it

Brentano transformed this from a metaphysical framework into a descriptive criterion for psychology.

Developments of the Concept After Brentano

Husserl (Brentano's student): Developed phenomenology as the systematic study of intentionality. He distinguished between:
- Noesis: the intentional act
- Noema: the intentional object
- He studied the structure of intentionality in different types of consciousness

Heidegger: Expanded intentionality from a property of consciousness to the structure of human existence (Dasein). Humans are "being-in-the-world"—their intentionality is fundamental to their being.

Searle: In contemporary analytic philosophy, attempted to naturalize intentionality as a biological property of the brain, like digestion for the stomach.

Philosophical Problems of Intentionality

Problem of non-existent objects: I can think about a unicorn or a fictional character. How can my mental state be "about" something non-existent? This challenges realist theories of intentionality.

Problem of indeterminacy: My intentionality toward "water"—is it toward H2O? Toward the clear liquid? Toward what quenches thirst? Quine raised the problem of indeterminacy of reference.

Problem of naturalization: How does intentionality arise from non-intentional physical processes? This is the central challenge for contemporary materialism.

Intentionality and Belief in God

Although Brentano did not use intentionality as a direct argument for belief, later philosophers saw important connections:

The argument from intentionality: If intentionality is a fundamental feature of mind and cannot be reduced to matter, this points to a non-material nature of reality. Richard Swinburne and others developed this.

Divine intentionality: In philosophical theology, God is absolute intentionality—His knowledge and will are directed toward everything perfectly. Human intentionality is a limited image of divine intentionality.

Problem of the origin of intentionality: Where did intentional capacity come from? Evolutionary explanation faces the challenge of explaining how non-intentional processes produce intentional capacity.

Contemporary Positions

Reductionists: (Dennett, Churchland) attempt to explain intentionality as an illusion or useful metaphor, reducible to computational processes.

Realists: (Searle, Fodor) insist that intentionality is real and irreducible, but differ in explaining its nature.

Phenomenologists: (Contemporary followers of Husserl) study the structure of intentionality without attempting to reduce or explain it in other terms.

Where We Stand in This Debate Today

Intentionality remains a central puzzle in philosophy of mind. Attempts at naturalization have not succeeded by consensus, and its role in understanding consciousness, meaning, and language continues to deepen. The debate is moving toward more precise understanding of types of intentionality and their relationships to consciousness, computation, and biology.

Brentano, by identifying intentionality as the distinguishing feature of mind, opened a door that has not yet been closed. Whether intentionality points to a non-material nature of mind, or is ultimately amenable to naturalistic explanation, remains an open question standing at the heart of our understanding of ourselves and reality.

For Advanced Reading

- Advanced level: Tim Crane's contemporary analysis of intentionality
- Franz Brentano, Psychology from an Empirical Standpoint (Routledge, 1995 [1874])
- Edmund Husserl, Logical Investigations (Routledge, 2001 [1900-1901])
- John Searle, Intentionality (Cambridge UP, 1983)
- Tim Crane, Elements of Mind (Oxford UP, 2001)
- "Theme: Mind and Consciousness" page on the website