The idea that chances are facts about real possibilities is – to many – an outlandishly metaphysical claim. It makes chance seem more like a philosopher's fantasy than anything else. One way of avoiding the idea that chances are facts about possibilities is to attempt to identify some non-chancy facts in the actual world which constitute the basis of probabilities. What I call actualist approaches thus maintain that chances are mind-independent and real, but hold that they are reducible to ‘this-worldly’ phenomena.

Actualist interpretations of chance

The actualist approach is associated with David Hume's famous discussion of the concept of causation. Hume observed that the concept of causation appeared to involve a necessary connection between cause and effect: given the cause, the effect must happen. But upon close inspection, Hume found that there was no observable correlate of such necessary connections. Exactly what conclusion Hume drew from this is still disputed, but one very influential interpretation of his thought is that he believed therefore that causation was in reality nothing more than the constant conjunction of two types of event. Seeing two events of a particular type occur together in time and space, again and again, produces in us a belief that they are causally connected, and that belief has an associated feeling that the connection is necessary.