IB Philosophy 6.2.3 Causality and Determinism Notes

The Nature of Causality

1. When a billiard ball strikes another and the second ball moves, we instinctively say the first ball caused the second to move, but what exactly is this relation of causation?
2. This question lies at the heart of philosophy of science and connects directly to the Unit 6 question: are all elements of the universe, including human action, ultimately determined?
3. David Hume offered the most influential philosophical critique of causality.
   1. In his Treatise of Human Nature (1739) and Enquiry Concerning Human Understanding (1748), he argued that we never directly perceive any necessary connection between cause and effect, meaning we never see that the first event had to produce the second.
   2. All we actually observe is one event followed by another.
   3. We only observe one event regularly followed by another, which Hume called constant conjunction. The impression of necessary connection is a product of habit, not perception.
4. Hume's regularity theory reduces causation to three features:
   1. the cause is contiguous (adjacent in space and time) to the effect;
   2. the cause comes before the effect; and
   3. similar causes are always followed by similar effects (constant conjunction).
5. The radical implication of Hume's argument is that causation is a habit of the mind, not a feature of the world itself.
6. When we expect the future to behave like the past (the principle of the uniformity of nature), we are relying on past experience to justify a belief about future experience, which is circular: we cannot use induction to justify induction.
7. Immanuel Kant responded in his Critique of Pure Reason (1781) by arguing that causality is not something we discover out in the world. Rather, it is a built-in framework the human mind uses to organise experience, something we bring to experience rather than find in it.
8. For Kant, the law of causality (the principle that every event must have a cause) is what he called an a priori synthetic principle.
   1. 'A priori' means it is known before any particular experience.
   2. 'Synthetic' means it genuinely tells us something about the world, rather than just defining a word.

1. A priori synthetic knowledge tells us something real and substantial about the world (it is not just a definition), yet we know it before any particular experience, because without it we could not have organised experience at all.
2. The debate between Hume and Kant sets up a fundamental tension in philosophy of science (see also 6.1.1): is causal knowledge genuinely revealing the structure of reality, or is it something the human mind imposes on experience in order to make sense of it?
3. Contemporary counterfactual theories of causation (developed by David Lewis) propose that 'A caused B' means: if A had not occurred, B would not have occurred either. Instead of asking what actually happened, these theories ask what would have happened in other possible situations, shifting the analysis from observed regularities to counterfactual scenarios (imagined cases of 'what if?').
4. The nature of causality matters enormously for science because scientific explanation typically involves identifying causes. If Hume is right that we can never observe causation directly, this raises deep questions about whether science delivers truth about the world's causal structure.

Physical Laws: Description or Governance?

1. Science expresses causal relationships through physical laws, mathematical regularities such as Newton's laws of motion or the laws of thermodynamics. But a crucial philosophical question is whether these laws merely describe patterns or genuinely govern the behaviour of nature.
2. The regularity view (following Hume) treats laws as summaries of observed regularities. They tell us what has happened and what will likely happen, but they do not compel events to occur.
3. The rival necessitarian view (championed by Dretske, Tooley, and Armstrong) holds that laws express real necessitation relations between types of things: it is not just that copper always has conducted electricity, but that being copper genuinely forces conduction. Nature does not merely happen to behave lawfully; it must.
4. The contrast between accidental and lawlike generalisations motivates the necessitarian position.
   1. ‘All gold is yellow’ appears to be a genuine law of nature, holding with a kind of necessity that goes beyond mere observation.
   2. ‘All the coins in my pocket are silver,’ by contrast, is a mere accident, one that could easily have been otherwise.
5. The regularity theorist, who identifies laws with observed patterns, struggles to explain this difference: both statements describe exceptionless regularities, yet one seems necessary and the other does not.