In the ancient world cities were nearly nations unto themselves – they existed within walls, with their own laws and customs, generally centered on the common purpose of trade. This is not as much the case in the modern world, but we still tend to divide ourselves city by city in terms of sports teams, accents, music and culture, and still tend to generalize the character of people from other cities. It follows, then, that in the Bible cities represent various doctrines – collections of inter-related ideas about spiritual reality. Such doctrines can be based on anything from the Lord’s true teachings – the New Jerusalem seen by John in Revelation – to the falsity and heresy of Sodom and various cities obliterated by the people of Israel at God’s command. On the most personal level, a city can also represent the natural mind of one person – which makes sense since we each to some extent have our own doctrine and our own set of ideas and beliefs.

1297. 'And let us burn them thoroughly' means the evils that stem from self-love. This is clear from the meaning of 'to burn, a burning, fire, sulphur, and bitumen' in the Word, where they have reference to evil desires, chiefly to those that belong to self-love, as in Isaiah,

Our holy house, and our splendour, where our fathers praised You, has been made into a blaze of fire, and all our pleasant places have been made into a waste. Isaiah 64:11.

In the same prophet,

Conceive chaff, bring forth stubble. Your wind is a fire that will consume you. Thus the peoples will be burnings of lime; [like] thorns cut down they will be burned in the fire. Isaiah 33:11-12.

And there are many other examples besides these. 'Burning' and 'fire' have reference to evil desires because they possess similar characteristics.