IB Philosophy 3.2.1 Scepticism Notes

Can We Know Anything at All?

Ancient Scepticism: Pyrrhonism and the Academy

1. The sub-theme of Problems of Knowledge (3.2) turns from the positive questions of 3.1 (what knowledge is, what truth is, what the sources of knowledge are) to the challenges that threaten to undermine knowledge entirely. This topic examines scepticism: the philosophical position that genuine knowledge may be impossible, or at least far more limited than we ordinarily assume.
2. The IB syllabus poses three interconnected questions: "Can we know anything at all?", "What are the necessary and sufficient conditions of knowledge?", and "Does knowledge require certainty?" These questions strike at the foundations of everything explored in 3.1 and challenge the very possibility of knowledge itself.
3. Ancient Greek scepticism provides the historical origin of the debate. Pyrrho of Elis (c. 360-270 BCE) argued that for every argument supporting a claim, an equally strong argument can be found against it.
4. The appropriate response is epochē (suspension of judgement): we should withhold belief on all matters that go beyond immediate experience, achieving ataraxia (tranquillity) through the abandonment of dogmatic claims to knowledge.
5. Consider: honey tastes sweet to a healthy person but bitter to someone with jaundice, raising the question of which perception reveals the honey's true nature.
6. The Pyrrhonist concludes that we cannot determine which experience corresponds to reality and therefore suspends judgement.
7. Academic scepticism, associated with Arcesilaus and Carneades of Plato's Academy, took a more moderate position.
8. They argued that no perception comes with a built-in guarantee of accuracy, since every impression that feels real could, in principle, be false.
9. They called this the kataleptic impression problem (from the Greek for "grasping", a perception that seems to grip reality directly): if we cannot tell from the inside whether what we perceive is real or a convincing fake, certainty is impossible.
10. Since we can never be certain that any impression truly corresponds to reality, certainty is unattainable. Carneades argued we can still act rationally by following the most probable impressions: those that are vivid, consistent with other impressions, and have been tested from multiple angles.

Descartes and the Modern Sceptical Method

1. René Descartes transformed scepticism from an end in itself into a philosophical method. In the Meditations on First Philosophy(prescribed text 10.3), Descartes employed methodological doubt: systematically doubting everything that could possibly be doubted in order to find an indubitable foundation for knowledge.
2. His sceptical arguments, the dream argument and the evil demon hypothesis, remain among the most powerful arguments in philosophy.
3. Descartes' dream argument observes that we cannot reliably distinguish dreaming from waking experience. If our current experience might be a dream, then we cannot be certain of anything we perceive.
4. His evil demon hypothesis imagines a powerful deceiver who systematically produces false experiences, raising the possibility that all our beliefs about the external world could be mistaken.
5. The modern equivalent of Descartes' evil demon is the brain in a vat scenario, popularised by Hilary Putnam. Imagine that your brain has been removed from your body and placed in a vat of nutrients, connected to a computer that simulates normal experience.
6. You would have no way of knowing that your experiences are artificial. This thought experiment illustrates the sceptic's challenge: how can we rule out systematic deception?
7. The overarching Unit 3 question, "Can I know anything at all?", receives its most direct treatment in this topic. Scepticism does not merely question particular beliefs ("Is that really a sheep?") but challenges the very possibility of knowledge.
8. If the sceptic's arguments succeed, then the entire framework of justified true belief (introduced in 3.1.1) collapses.

Self-Refutation, JTB, and the Stakes of Scepticism

1. However, scepticism itself faces a self-refutation objection. If the sceptic claims to know that knowledge is impossible, their claim undermines itself.