Flatland is a novel told in first person by the square, one of the inhabitants of the «land of Flatland». This land is like a big sheet of paper: a world in two dimensions, where the inhabitants are squares, triangles, hexagons, pentagons, etc. The first part of the book it is a description of Flatland: its characteristics, the people and its customs. The second part narrates the adventures of the main character, who discovers other different worlds with more dimensions. In a certain moment, the square has a dream of a world of One Dimension. However, he wakes up and realizes that everything has been a dream.

If my Readers have followed me with any attention up to this point, they will not be surprised to hear that life is somewhat dull in Flatland. (…) I speak now from the aesthetic and artistic point of view when I say that life with us is dull; aesthetically and artistically, very dull indeed (Edwin A. Abott, Flatland,Penguin Books, London 1998, p. 39).

On one occasion, the square notices a strange presence in his house: a circle changing in size. He does not know exactly what it is, until he starts a conversation with this creature (the changing circle). He realizes that it is a sphere, which is crossing Flatland, and he gets to know that the changing in the size is due to the crossing, because he only sees the intersection between the sphere and the plane. There is a very interesting conversation between the sphere and the square:

STRANGER. Pooh! What do you know of Space? Define Space.
I. Space, my Lord, is height and breadth indefinitely prolonged.
STRANGER. Exactly: you see you do not even know what Space is. You think it is of Two Dimensions only; but I have come to announce to you a Third —height, breadth and length.
I. Your Lordship is pleased to be merry. We also speak of length and height, or breadth and thickness, thus denoting Two Dimensions by four names.
STRANGER. But I mean not only three names, but Three Dimensions.
I. Would your Lordship indicate or explain to me in what direction is the Third Dimension, unknown to me?
STRANGER. I came from it. It is up above and down below.
I. My Lord means seemingly that it is Northward and Southward.
STRANGER. I mean nothing of the kind. I mean a direction in which you cannot look, because you have no eye in your side.
I. Pardon me, my lord, a moment’s inspection will convince your Lordship that I have a perfect luminary at the juncture of two of my sides.
I. STRANGER. Yes: but in order to see into Space you ought to have an eye, not on your Perimeter, but in your side, that is, on what you probably call your inside; but we in Spaceland should call it your side.
I. An eye in my inside! An eye in my stomach! Your Lordship jests.(Flatland, pp. 82-83)

This way, the sphere proclaims the “Gospel of the Three Dimensions” to the square, and takes it to the world of three dimensions. The square, excited, asks if there can be a fourth or fifth dimension, but gets angry when the sphere answers no. Anyway… if a sphere is the conjunction of infinite circumferences, what will be of the conjunction of infinite spheres?

I. But my Lord has shewn me the intestines of all my country-men in the Land of Two Dimensions by taking me with him into the Land of Three. What therefore more easy than now to take his servant on a second journey into the blessed region of the Fourth Dimension, where I shall look down with him once more upon this land of Three Dimensions, and see the inside of every three-dimensioned house, the secrets of the solid earth, the treasures of the mines in Spaceland, and the intestines of every solid living creature, even of the noble and adorable Spheres.
SPHERE. But where is the land of Four Dimensions?
I. I know not: but doubtless my Teacher knows.
SPHERE. Not I. There is no such land. The very idea of it is utterly inconceivable. (Flatland, p. 102)

At the end of the story, the square returns to Flatland, and begins to proclaim that «Gospel», but nobody believes in his words and the authorities from Flatland send him to prison, from where he writes this book. This story, let us say, ends badly (sorry about the spoiler)… but the story puts a big question in front of us: Is a fourth dimension possible? Where we can find it? Where we can find an Hypercube? Maybe the Letter to the Ephesians can give us a key of interpretation. Maybe Salvador Dalí read  the Letter to the Ephesians. Maybe Salvador Dalí found a Four-Dimensional Hypercube in the writings of Saint Paul. And maybe Dalí painted it in 1954:

And that Christ may dwell in your hearts through faith; that you, rooted and grounded in love, may have strength to comprehend with all the holy ones what is the breadth and length and height and depth, and to know the love of Christ that surpasses knowledge, so that you may be filled with all the fullness of God. (Ephesians 3:17-19)

Dalí, Salvador – Corpus Hypercubus, 1954, Metropolitan Museum of Art, New York