IB Philosophy 3.1.3 Sources of Knowledge Notes

Perception as a Source of Knowledge

The Empiricist Account and Kant's Active Perception

1. Topics 3.1.1 and 3.1.2 examined what knowledge is and the role that truth plays in constituting it. This topic completes the 3.1 sub-theme by asking a practical question: where does knowledge come from?
2. The IB syllabus identifies three primary sources: perception, reason, and testimony.
3. Perception (sensory experience) is the most immediate source of knowledge. We learn about the world by seeing, hearing, touching, tasting, and smelling it.
4. The empiricist tradition (discussed in 3.1.1) holds that perception is the primary source of all knowledge: John Locke's tabula rasa thesis (introduced in 3.1.1) claims that the mind begins as a blank slate, and all content arrives through sensory experience.
5. However, perception is not a passive reception of data. As Kant argued (discussed in 3.1.1), the mind actively structures sensory input through innate categories (causation, substance, space, time).
6. What we perceive is not raw reality but reality as organised by our cognitive apparatus. Perception is already a form of interpretation.
   1. Consider watching one billiard ball strike another: you perceive the first ball moving, the collision, and the second ball moving away.
   2. As Hume argued, you never actually perceive causation itself.
   3. You only perceive a sequence of events. Kant's point is that the mind supplies the category of causation, structuring the raw sequence into a causal relationship.
   4. Without this mental contribution, we would experience a chaotic stream of sense impressions rather than an orderly world of objects causing effects.
7. As Descartes argued (see 3.1.1), the senses sometimes deceive us, which raises the question of whether perception alone can serve as a reliable foundation for knowledge. If we cannot always tell the difference between genuinely seeing something and being fooled by an illusion or a dream, then whether perception counts as a source of knowledge depends on whether we can find clear criteria for spotting the reliable cases.

Phenomenology and Embodied Perception

1. Phenomenologists, philosophers who study the structure of lived, first-person experience, offer a richer account of what perception actually involves. Husserl argued that all consciousness is intentional: every act of awareness is always consciousness of something, directed towards an object.
2. Merleau-Ponty extended this insight by arguing that perception is not merely a source of knowledge but the fundamental way in which we are related to the world. For Merleau-Ponty, perception is always embodied: it involves our whole body, not just our sense organs, and it places us in a lived relationship with our environment.
3. Consider a blind person using a cane to navigate a room: the cane becomes an extension of the body, absorbed into the perceiving subject.
4. The person does not perceive the cane pressing against their hand but rather perceives the texture and contour of the ground through the cane.
5. For Merleau-Ponty, this shows that perception is not a matter of receiving sensory data through fixed channels but of the body actively reaching out into the world. The boundaries of the perceiving body are flexible and extend through the tools and practices we inhabit.
6. This challenges the empiricist picture of perception as passive data reception: the blind person's cane-mediated perception is genuine perception, not inference from touch sensations.

Realism, Cultural Conditioning, and the Limits of Perception

1. The question of whether perception gives us knowledge of reality as it truly is or only of appearances is central to epistemology. Direct realists hold that we perceive the world as it is.
2. Indirect realists hold that we perceive representations (sense data) caused by external objects, while idealists deny that a mind-independent external world exists at all.
3. These positions will be examined in depth in 3.2.2 (Theories of Perception).
4. Perception also raises questions about cultural conditioning. As Gombrich argued in the context of aesthetics (discussed in 2.3.2), what we perceive is shaped by the schemata (mental frameworks) we bring to experience.
5. Two people looking at the same scene may literally see different things because their cultural backgrounds, training, and expectations differ.
6. The overarching Unit 3 question, "Is knowledge culturally dependent?", is particularly relevant here. If perception is shaped by culture, then perceptual knowledge may be culturally relative to some degree.