To build something generally means to put together a variety of simpler pieces to make a useful and more complex structure, as to build a house out of wood or bricks, and it is commonly used this way in the Word. In the land of Shinar men wished to build a tower, and in the new testament Jesus advised that a wise man should build his house on a rock. But in a representative sense the meaning is to build a mental and spiritual structure, like the doctrine of a church or the individual concepts of spiritual reality in a single mind. The building materials are representative also. The tower of Babel was built of brick, which is man-made rock, or representatively, man-made "truths", that is"truths" not from God but ideas of spiritual reality thought out by men. The house that the wise man would build was founded on a natural or "God-made" rock, which means a truth from the Word.

In general, trees represent the deepest and most significant intellectual concepts: the ones that come to us most directly from the Lord. This varies depending on us and our states: the people of the Most Ancient Church, who were in a state of loving the Lord, understood truth automatically and internally through what the Writings call "perception"; people in lower states (including most of us) have to work a little harder to learn it from the Word and by willing to follow the Lord. In other parts of the Bible, especially in the prophets and New Testament parables, the meaning of "tree" is broader, meaning not just a person's intellectual concepts but the whole person.

'Trees,' as in Joel 1:10-12, signify knowledges.