"A man who says that no patriot should attack the war until it is over... is saying no good son should warn his mother of a cliff until she has fallen"

This quote by Gilbert K. Chesterton is a criticism of those who think that it is wrong to slam a war while it is still continuous. Chesterton is recommending that this kind of thinking belongs to telling a child not to caution his mother of a cliff until she has actually already fallen off it. In other words, it is far too late to assist her once she has actually already fallen. Chesterton is implying that it is much better to speak up against a war while it is still happening, instead of waiting till it is far too late. He is suggesting that it is the responsibility of a patriot to speak out against a war if they believe it is wrong, rather than waiting until it is over. By doing so, they can help to prevent more suffering and damage.