Once upon a time on a planet far away there lived a tribe on a small, lush island in a grand, rough ocean. Nobody had ever left the island. Neither had anybody from outside ever visited.
The village sage said, based on the curvature of the land she observed, that their world must be much bigger than the island. Who knows what would lie beyond the horizon.
A few sharp-eyed villagers claimed that when the wheather is just right, you could see another island just beyond the horizon.
Lots of young people dwelled the island, had great fun sometimes. In a quiet moment, some of them sometimes dreamed of the wild adventures and fantastic discoveries that might lurk out there.
The village carpenter claimed it would be possible to build a device called a 'ship' that just might take a few brave explorers to the other island. Because the seas were so rough, it would have to be big. The large amount of wood needed would not be available for something else of course.
In the evenings spent around the fire, village storytellers could go on hours and hours narrating the adventures of imaginary heroes discovering other island worlds.
But nobody ever built a ship, and nobody ever departed. The tiny island civilization became tired and old. Sure they managed to administer their island well, they kept the population within limits, it wasn't all that bad. All went on for quite some centuries. Then, the volcano in the center of the island burst out and that was the end of it.
A few thousand miles away there was another island on which there lived another tribe. Every year, they cut down a few trees and saved up the wood for a ship...
Just image going out at night, looking at a particular star knowing an explorer ship from Earth has visited it. Or knowing life or even people from Earth were actually living there. Would that not be one of the grandest things ever?
More on the terrifying side, it is well known occasionally extinction events (comet impact, climate change,...) happen on our planet, wiping out almost any advanced life form. In order to secure the long-term future of mankind, many renown scientists include Stephen Hawking propose to invest in colonizing other worlds.
A third reason comes from the philosophic stance that sees humanity, the only technologically powerful species on Earth, as guardian of life on Earth. Currently, we are discovering many planets outside our solar system. On some of them, life may be possible but does not exist yet. In that light, it is humanity's duty to explore the universe to seek out new life, and bring life on planets where there is none.
Sadly, the benefits of interstellar projects will never bene for generation that starts it. Therefore, it will be next to impossible to convince sponsors to put massive resources in such projects. It is always going to be the next generation's problem until it is too late. However, many will find a still reasonable to contribute somewhat to the dream of a second home planet for humanity. That is why the FMF proposes to slowly gather the required resources in a long-term fund comparable to a sovereign wealth fund or the fund of the Nobel Prize Foundation.
The Duomo di Milano (Milan Cathedral) took over 500 years to build.
The gathering of the funds, the construction of the ships and the voyage itself will necessarily take at least a century, as dictated by laws of physics for which there is solid evidence. The FMF sees this as an opportunity, not a threat. Humanity has overcome challenges of similar timescales before: the best example is the construction of the great cathedrals in Europe in the Middle Ages. The people that started the construction works knew perfectly they would not see their completion. But they did so anyway.
In an similar way, the construction of great starships and their voyages could unite and inspire humanity throughout the third millennium.