Eating of the tree of knowledge represents using our own logic and reason to try to figure out and understand the Lord, something which is beyond us and which, ultimately, we have to simply accept. This was forbidden to the people at this stage of the Most Ancient Church because the Lord knew that if they did, they would lose their innocent acceptance of the Lord's love and leading, and would question it instead. This is represented by the idea that they would "die."

(References: Arcana Coelestia 198, 200, 201, 202, 203)