There's magic here, of sorts. Cloistered from the rest of the world, a garden harkens back to the earliest halcyon days of humanity, when the sons of God rejoiced and His newest children walked blameless and naked below the stars. Here, within these walls, lies a remnant, an ember, of how things ought to be, protected from the terrors of outside by brick and stone and wood and metal and concrete.
How it ought to be. But... it is not. Things are not as they should be, and without walls, any attempt to reverse even but a bit of the fall, even locally, will be swamped by the chaos that lurks at the corners of our vision, just beyond the horizon, bubbling beneath the surface of someone we know very little of after all, despite our delusions to the contrary. Walls are a force for good. Walls divide – but division is necessary for diversity, for beauty, for life itself. The first thing ever declared good was the division of light from darkness. Something there is that would have a uniform twilight covering all of existence.
Life itself depends on boundaries. From the smallest organelle to the skin of the most complex organism, life is a series of walls within walls within walls. An environment good for one thing is not good for another. Walls enable a separation that enables flourishing. Even the simplest form of life requires a wall around it to mark off it's interior. “This far,” says the cell membrane, “and no further, must the external environment intrude.” What a foolish thought it is to think that tearing down all divisions would bring utopia, rather than the bland uniformity of hell.
There are two ways to die, the chaos of fire or the cold order of ice. The first from no barrier, the second from no diversity. To avoid either fate requires walls.