What Is Philosophy?

1. Introduction

What Is Philosophy? (Qu’est-ce que la philosophie ?, 1991) is Deleuze and Guattari’s final major collaboration and their most direct attempt to define what philosophy does. Rather than treating philosophy as contemplation, critique, or communication, the book presents it as a distinctive creative practice: the invention of concepts on a field of immanence.

The work is not an introductory handbook to existing doctrines. It assumes familiarity with the history of philosophy and develops a systematic vocabulary—concept, plane of immanence, conceptual personae, percepts and affects, geophilosophy—to distinguish philosophy from science and art while insisting on the equal rigor of all three.

Written late in both authors’ lives and careers, the book reflects on the conditions under which thinking becomes possible, the dependence of thought on its social and geographic “earth,” and the challenges posed by capitalism, technoscience, and the contemporary university. Readers have approached it both as a summation of earlier works such as Anti‑Oedipus and A Thousand Plateaus and as an autonomous treatise that recasts key questions about what counts as philosophy, how it relates to other practices of knowledge and creation, and what its future might be.

2. Historical Context and Publication

Intellectual and Political Context

What Is Philosophy? was written in the late 1980s and published in 1991, at a moment often described as “post-structuralist” and “post–Cold War.” Commentators link the work to several overlapping contexts:

Some scholars emphasize the book’s engagement with contemporaries such as Foucault, Lyotard, Derrida, and analytic philosophy of science; others stress its roots in Deleuze’s long-term studies of Spinoza, Nietzsche, and Bergson, and Guattari’s work in institutional psychotherapy and political activism.

Publication History

The work has no elaborate preface but is often read as marked by awareness of mortality: Guattari died in 1992 and Deleuze in 1995. This has led interpreters to situate the book at the threshold between late-20th-century debates about structuralism and newer concerns with globalization, media, and neoliberalism, while also viewing it as a final reflection on the vocation of philosophy itself.

3. Authorial Collaboration and Composition

Deleuze and Guattari’s Collaborative Method

Gilles Deleuze (a philosopher by academic training) and Félix Guattari (a psychoanalyst and political activist) had collaborated since Anti-Oedipus (1972). Accounts by the authors and their interlocutors describe a non-hierarchical but differentiated division of labor:

They themselves resisted clear separations, presenting the books as joint works in which ideas were co-produced.

Composition of What Is Philosophy?

The book was drafted between roughly 1988 and 1991. Biographical studies suggest that both authors were dealing with serious health issues, which some commentators see echoed in the text’s recurrent concern with aging, the end of a life, and the future of thought.

Composition features noted by scholars include:

• A more linear structure than A Thousand Plateaus, organized into three named parts.
• Reuse and consolidation of earlier themes—desire, deterritorialization, assemblages—into a more explicitly “philosophical” idiom.
• Intensive discussion between the authors about the distinct roles of philosophy, art, and science, informed by Guattari’s work with artists and media projects and Deleuze’s prior books on cinema.

Editorially, the French edition at Éditions de Minuit followed the model of their earlier collaborations, with minimal paratext and a compact, dense layout intended for a philosophically literate readership.

4. Structure and Central Arguments

Overall Structure

The book is divided into three parts, each addressing a specific problem:

Central Arguments

1. Philosophy as creation of concepts
   Deleuze and Guattari argue that philosophy is defined by the creation of concepts, not by contemplation, reflection, or communication. Concepts are presented as complex multiplicities with heterogeneous “components” and internal “zones of neighborhood,” rather than as general abstractions or mental images.

2. Plane of immanence
   Concepts exist on a plane of immanence, a pre-philosophical field that each philosophy sketches in its own way. Different philosophical traditions are said to draw different images of what thought is capable of, and these images condition which concepts can be created.

3. Conceptual personae
   The book introduces conceptual personae—figures like the friend, the idiot, or the Overman—that dramatize ways of thinking and guide conceptual invention. These personae are treated as structural roles within a philosophy, not merely biographical details.

4. Distinction from art and science
   A key claim is that philosophy, science, and art are irreducible yet interrelated. Philosophy creates concepts, science constructs functions on planes of reference, and art composes percepts and affects on planes of composition. Debates in the secondary literature concern how sharply these boundaries should be drawn.

5. Geophilosophy and deterritorialization
   The emergence of philosophy is tied to specific “earths” and “peoples,” notably Greek and modern European contexts, through processes of deterritorialization and reterritorialization. The book links conceptual creation to geographical, political, and social transformations.

6. Chaos and the brain
   In the final part, thought is framed as a response to chaos. Philosophy, science, and art each carve out partial consistencies from chaos. The brain is described as a site where these different kinds of consistencies intersect, raising questions about the material conditions of thinking.

5. Key Concepts and Technical Vocabulary

What Is Philosophy? develops a compact technical lexicon. The following terms are central within the book itself:

Scholars differ on how strictly these terms should be defined: some treat them as precise technical tools, others as heuristic figures whose meaning shifts across Deleuze and Guattari’s writings.

6. Legacy and Historical Significance

Place in Deleuze and Guattari’s Oeuvre

What Is Philosophy? is widely regarded as a culminating statement that systematizes ideas dispersed across earlier works. Many commentators treat it as:

• A clarification of the status of concepts, assemblages, and deterritorialization.
• A more explicit account of immanence and the role of philosophy vis‑à‑vis other disciplines.

Others see it instead as a distinct late project, noting changes in tone, increased attention to aging and finitude, and a more didactic structure.

Influence Across Fields

The book’s impact has extended beyond academic philosophy:

Ongoing Debates

Scholarly reception has raised several enduring questions:

• Whether the account of science as oriented to functions and reference oversimplifies scientific practice.
• To what extent the book overcomes, or reproduces, Eurocentric narratives when locating the origin of philosophy in Greece and modern Europe.
• How its commitment to immanence and conceptual creation relates to normative and political questions, including critiques of capitalism and the university.

Despite disagreements, the work is now a standard reference for discussions of what philosophy is, what philosophers do, and how philosophical activity can be situated within broader constellations of art, science, and social life.