874. 20:15 And anyone not found written in the Book of Life was cast into the lake of fire. This symbolically means that those who had not lived in accordance with the Lord's commandments in the Word and did not believe in the Lord were condemned.
That the Book of Life symbolizes the Word, and to be judged on the basis of that book means, symbolically, to be judged in accordance with the Word's truths, may be seen in nos. 256, 259, 295, 302, 309, 317, 324, 330 above. Moreover, no one is found written in the Book of Life but someone who has lived in accordance with the Lord's commandments in the Word, and who believed in the Lord. This, therefore, is what is meant.
That someone who does not live in accordance with the Lord's commandments in the Word is condemned, is something that the Lord teaches in John:
If anyone hears My words and does not believe, I do not judge him... (He) has that which judges him: the Word that I have spoken will judge him in the last day. (John 12:47-48)
And that someone who does not believe in the Lord is condemned, also in John:
He who believes in the Son has eternal life, while he who does not believe the Son shall not see life, but the wrath of God abides on him. (John 3:36)