“Reality is not a function of the event as event, but of the relationship of that event to past, and future, events.”

Session 729, Page 520
The “Unknown” Reality: Volume Two, (1979)

Futurewise (1998)

Speech in the House of Commons, July 8, 1920 "Amritsar" http://lachlan.bluehaze.com.au/churchill/am-text.htm ; at the time, Churchill was serving as Secretary of State for War under Prime Minister David Lloyd George
Early career years (1898–1929)
Context: However we may dwell upon the difficulties of General Dyer during the Amritsar riots, upon the anxious and critical situation in the Punjab, upon the danger to Europeans throughout that province, … one tremendous fact stands out – I mean the slaughter of nearly 400 persons and the wounding of probably three to four times as many, at the Jallian Wallah Bagh on 13th April. That is an episode which appears to me to be without precedent or parallel in the modern history of the British Empire. … It is an extraordinary event, a monstrous event, an event which stands in singular and sinister isolation.

Response to a journalist when asked what is most likely to blow governments off course.
The quote is also given as "Events, my dear boy, events", with the word "my", but it may never have been uttered at all.
[What they didn't say: a book of misquotations, Knowles, Elizabeth M., Oxford University Press, 2006, vi, 33]
Disputed

The Phoenix, a Linguistic Phenomenon, ch. 1
Fragments of a Poetics of Fire (1988)

Source: The Nature of Personal Reality (1974), p. 355: session 654: April 9, 1973