Black swans have always been around. Because Europeans (who have always thought they knew everything) had never seen one, they didn’t think they existed. They had a popular proverb that had variations like, “As unlikely as a black swan,” or facetiously, “As rare as a black swan.”
In 1697, Dutch explorers to Western Australia became the first Europeans to see that black swans had long been living happily there. The new proverb regarding black swans refers to them as knowledge or information that is hidden. Something that you don’t know you don’t know.
When Yahweh’s 40 year old nation was finally entering land Canaan’s descendants were occupying, they got very clear instructions from Him about how to take the city of Jericho. From that victory, they marched toward the next town on the map, Ai. When they attacked the town, the inhabitants drove them back out of the valley and killed Israelis in the process.
Deciding that there was something they didn’t know they didn’t know, Israel inquired of the Lord and were informed that He was not fighting with them until they dealt with Achan for stealing some of the items that should have been devoted to Yahweh as offering from the possessions of deceased citizens of Jericho.
They took the revelation and acted on it, killing Achan and his household. Then, before approaching Ai again, asked Yahweh for His strategy for the attack. He gave it to them and they prevailed.
Its always possible, and usually likely, that there is something we don’t know that we don’t know. Always being attentive instead of presumptive, always being humble and able to be informed and empowered by the Spirit when He knows something we don’t will make us successful more often at fulfilling His desires. Presuming that there are hidden things that He wants to tell us about will make it more likely we get the revelation from Him.