“The Christian ideal has not been tried and found wanting. It has been found difficult; and left untried.”
Chesterton argues from within his Christian framework that failure to live up to an ideal should not automatically be treated as evidence that the ideal itself has been disproved.
Source details
What's Wrong with the World, Part One, Chapter V, ‘The Unfinished Temple,’ Project Gutenberg #1717. Chesterton argues that the Christian ideal was ‘found difficult; and left untried’ while claiming that older ideals failed through incomplete practice rather than exhaustion. It remains explicitly Christian and historical polemic rather than a neutral empirical rule about why institutions or ideals fail.