Why did David Hume think people expect similar events to occur again?

David Hume argued that people expect similar events to occur again not because of rational deduction, but because of custom and habit.12

Hume observed that when we witness two types of events—such as a moving billiard ball striking a stationary one—we repeatedly see them occur in a specific order and proximity, a phenomenon he called "constant conjunction". Because we are long accustomed to this sequence, our minds develop a feeling of "determination" or compulsion to anticipate the second event whenever the first occurs.134

This expectation is a psychological response rather than a logical one. Hume famously noted that there is no rational way to prove that the future must resemble the past, as any attempt to justify this principle relies on circular reasoning. While we are psychologically compelled to believe in these causal connections, Hume maintained that these inferences are products of mental habit rather than reason. Consequently, he concluded that custom, not reason, is the "great guide of life".152