We know that numbers are important in the natural world and particularly in understanding the natural world through science. From the Writings of Emanuel Swedenborg we learn that numbers are important in a spiritual sense as well. From beginning to end, the Word (Bible) is filled with numbers, and one of its books is so named. Swedenborg explains the significance of these numbers in many of his works. In the Apocalypse Explained (§ 336) he says that numbers or measures denote the quantity of a thing in the natural sense and the quality of a thing in the spiritual sense. He also refers to the fact that numbers are used as a kind of language in the spiritual world, with each idea represented by a unique number, in a way that only those in the same heaven can understand (HH § 263; AC § 4495).