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Perception is our key to the world. It plays at least three different roles in our lives. It justifies beliefs and provides us with knowledge of our environment. It brings about conscious mental states. It converts informational input, such as light and sound waves, into representations of invariant features in our environment. Corresponding to these three roles, there are at least three fundamental questions that have motivated the study of perception. How does perception justify beliefs and yield knowledge of our environment? How does perception bring about conscious mental states? How does a perceptual system accomplish the feat of converting varying informational input into mental representations of invariant features in our environment?

This book presents a unified account of the phenomenological and epistemological role of perception that is informed by empirical research. So it develops an account of perception that provides an answer to the first two questions, while being sensitive to scientific accounts that address the third question. The key idea is that perception is constituted by employing perceptual capacities - for example the capacity to discriminate instances of red from instances of blue. Perceptual content, consciousness, and evidence are each analyzed in terms of this basic property of perception. Employing perceptual capacities constitutes phenomenal character as well as perceptual content. The primacy of employing perceptual capacities in perception over their derivative employment in hallucination and illusion grounds the epistemic force of perceptual experience. In this way, the book provides a unified account of perceptual content, consciousness, and evidence.

Table of Contents

Part I: Foundations
1. Perceptual Particularity
2. Perceptual Capacities

Part II: Content
3. Content Particularism
4. Fregean Particularism
5. In Defense of Perceptual Content

Part III: Consciousness
6. Perceptual Consciousness as a Mental Activity

Part IV: Evidence
7. Perceptual Evidence
8. Justification, Luminosity, and Credences
9. Perceptual Knowledge and Gettier Cases
10. Capacitism and Alternative Views

Book Symposia in Journals

  • Philosophy and Phenomenological Research with M.G.F. Martin, Casey O’Callaghan, and Michael Rescorla
  • Mind & Language with Christopher Hill, Nico Orlandi, and Ram Neta.
  • Analysis with Alex Byrne, Jonathan Cohen, and Matthew McGrath.


  • "One of the few books on perception that gives the reader a new theoretical approach, a critical overview of the state of the art, and an integration of the philosophy of perception with both epistemology and the empirical sciences. A significant resource for any course on perception." — Christopher Peacocke, Columbia University
  • "The Unity of Perception offers a brilliantly original and comprehensive theory of perception, perceptual consciousness and perceptual knowledge. Philosophers of mind and epistemologists, in particular, will find Schellenberg's book a rich source of insight and provocation." – Alex Bryne, Massachusetts Institute of Technology
  • "Susanna Schellenberg gives us wonderfully informed and penetrating discussions of the live issues in the philosophy of perception in charting the path to her own position - Capaciticism. We are all in her debt." — Frank Jackson, Australian National University and Princeton University
  • "Philosophers and psychologists have studied perception for as long as they've studied anything. But I cannot think of any earlier treatment of that topic that provides arguments that are as clear and explicit as the arguments in this important new book, or that situates its own commitments against the alternatives as usefully as Schellenberg does. Anyone developing an account of perception - its content, its epistemic force, its phenomenal quality - will now need to specify how their view differs from Schellenberg's." — Ram Neta, University of North Carolina at Chapel Hill
  • "Schellenberg's excellent book will undoubtedly have a wide audience among philosophers of mind and epistemologists. Among other virtues, it offers (i) innovative and plausible arguments for the superiority of representationalist theories of perception over disjunctivist and naive realist theories, (ii) the first systematic attempt to develop the view that the contents of perceptual states are robustly particular, with entities like Hillary Clinton and that table serving as their constituents, and (iii) a sustained defense of the idea that our concepts of perceptual evidence are externalist in character. The book is unique in the current literature in seeking accounts of the metaphysical and epistemological dimensions of perception that are mutually reinforcing." — Christopher Hill, Brown University
  • "The Unity of Perception is a splendid achievement. It fuses the representational, phenomenal, and epistemic dimensions of perception into a coherent whole, bound together by their common basis in the exercise of perceptual capacities. Central to the account is Schellenberg’s broadly Fregean theory of perceptual content, which assigns a pivotal role to modes of presentation (MOPs). Schellenberg develops the theory in impressive detail, applying it to a wide range of cases." — Michael Rescorla, UCLA, Philosophy and Phenomenological Research
  • "Capacities are powerful predictive, explanatory tools for theorizing about subjects, minds, and performance. According to The Unity of Perception, capacities anchor a systematic, far-reaching account of perception and perceptual consciousness." — Casey O’Callaghan, Washington University in St. Louis, Philosophy and Phenomenological Research
  • "The Unity of Perception is an ambitious and wide-ranging book—one that presents a unified account and then uses it to address Big Questions about perception . . . Schellenberg’s proposals are important, and will play a role in future discussion of these matters." — Jonathan Cohen, UCSD, Analysis 
  • ‘Rich and rewarding." — Matthew McGrath, Rutgers University, Analysis
  • "The Unity of Perception is an interesting and thought-provoking book. The central view—capacitism—and its broad implications for philosophy of perception, epistemology, philosophy of mind, and cognitive science make this book a valuable contribution to anyone working on perception, and I have no doubt that it will draw a great deal of well-deserved attention." — Arnon Cahen, Department of Cognitive and Brain Sciences, The Hebrew University, Perception


  • Perception: Epistemology and Mind, including a book symposium on The Unity of Perception with Chris Kelp, Jack Lyons, Louise Richardson, University of Glasgow
  • Perception: Particularity, Content, and Relation, University of Zürich
  • Perceptual Content: Workshop on The Unity of Perception with Susanna Schellenberg, University of Potsdam
  • The Unity of Perception: Workshop with Susanna Schellenberg, University of Tübingen
  • Philosophy of Perception, workshop on The Unity of Perception, TMU, Taipei

Author Meets Critics Sessions

  • Inter-American Congress of Philosophy 2019, Critics: John Campbell, Gabriel Greenberg, John Morrisson
  • APA Pacific Division Meeting 2019, Critics: M.G.F. Martin, Casey O’Callaghan, Michael Rescorla
  • 24th World Congress of Philosophy, Critics: Chris Hill, Nico Orlandi
  • APA Pacific Division Meeting 2018, invited symposium on The Unity of Perception with Jonathan Cohen, Mike Martin, Ram Neta
  • Southern Society for Philosophy and Psychology 2018, Critics: Alex Byrne, Jonathan Cohen, Matthew McGrath.