Take your pick from

coquetting, dallying, flightiness, flippancy, flirting, flummery, folly, fribble, frippery, frivolousness, fun, gaiety, game, giddiness, jest, levity, lightheartedness, lightness, nonsense, play, puerility, shallowness, sport, superficiality, toying, trifling, triviality, volatility, whimsicality, whimsy

In the beginning of the world they were flightiness.

In the beginning of the world they were flightiness.

Caprice (n.) 1. A sudden, unpredictable change, as of one's mind or the weather. 2. a tendency to change one's mind without apparent or adequate motive; whimsicality; capriciousness: With the caprice of a despotic king, he alternated between kindness and cruelty.

the unpredictability of our destiny/ fate