The heart means love. A good heart means love to the Lord and to the neighbor, while a hard or stony heart means the love of self or the world -- riches and things. When the psalmist asks the Lord to search his heart, he wants the Lord to see what it is that he loves. And we are what we love. What we eat may form our earthly body, but it's only temporary, what we love forms our spiritual body, beautiful or ugly as we have chosen. It's interesting to note that the first multi-cellular motion of our embryo is the pulsating that starts in a twist of blood vessel that is to become our heart, and the last motion of our natural body is our heartbeat. It is there for all of our natural life. And of course there is a beating heart in our spiritual bodies when we come to put them on.

404. Verse 14. And the heaven departed as a book rolled up, signifies that the spiritual man became closed up. This is evident from the signification of "heaven," as being the church in general and in particular; for the church is the heaven of the Lord on the earth; moreover, the church makes one with heaven by conjunction; therefore when "heaven and earth" are mentioned in the Word, the church internal and external is meant, for the internal of the men of the church is heaven with them, and their external is the world with them; and as "heaven and earth" signify the church internal and external so they signify the internal and external man, or the spiritual and the natural man; for as man in whom is the good of love and of faith is a church, so the church, in general exists from the men in whom the church is. This makes clear why it is that "heaven" here means the internal or spiritual man. It is said "the spiritual man," by which is meant the spiritual mind, which is the higher or interior mind of man, while the lower or exterior mind is called the natural man. The above is evident also from the signification of "departed as a book rolled up," as meaning that it became closed up; for the spiritual mind, which is, as was said, the higher or interior mind with man, is opened by truths applied to life, thus by goods, but it is closed up by falsities applied to life, thus by evils; and the closing up is as the rolling up of the scroll of a book. That this is so was made very clear by the appearances in the spiritual world when the Last Judgment was accomplished; for the mountains and the hills there then appeared sometimes to be rolled up as the scroll of a book is rolled up, and those that were upon them were then rolled down into hell. The cause of this appearance was this: that the interiors of their minds, through which somewhat of light from heaven had before flowed in, were then closed up. What takes place in general with many, takes place with everyone in particular of a like character, for in the spiritual world such as the general is, such is the particular (See in the work on Heaven and Hell 73). By "book" is meant a scroll, because in ancient times there were no types and thus no books like those at the present day, but there were scrolls of parchments; so "books" in Revelation mean scrolls, and "heaven departed as a book rolled up" means as a scroll rolled up; the same as in Isaiah:

All the host of the heavens shall waste away, and the heavens shall be rolled up as a book (Isaiah 34:4).