In Revelation 3:14-18 we find the well known passage about lukewarmness:
14 “To the angel of the church in Laodicea write:
These are the words of the Amen, the faithful and true witness, the ruler of God’s creation. 15 I know your deeds, that you are neither cold nor hot. I wish you were either one or the other! 16 So, because you are lukewarm—neither hot nor cold—I am about to spit you out of my mouth. 17 You say, ‘I am rich; I have acquired wealth and do not need a thing.’ But you do not realize that you are wretched, pitiful, poor, blind and naked. 18 I counsel you to buy from me gold refined in the fire, so you can become rich; and white clothes to wear, so you can cover your shameful nakedness; and salve to put on your eyes, so you can see."
I remember reading somewhere that this was best interpreted in relation to the geography of the place and, specifically, its water supply. Whilst very well placed for trade, Laodicea was not established near an adequate water supply and water had to be piped in ten or so miles from Colossae which had an abundant cold water supply. By the time the water arrived it was lukewarm. About six miles away was Hierapolis which boasted hot springs but, similarly, by the time the water arrived it, too, was lukewarm.
The point here, is that both hot and cold water had a usefulness not present in lukewarm water. The cold was used for drinking and gardening, and the hot for washing etc. Lukewarm water was good for nothing.
Verse 15 contains the phrase, "I wish you were either one or the other!" Does Jesus wish that we were atheists rather than in-between?* That's what it looks like on first reading and seems to be the majority interpretation when researched. But, the explanation with respect to the water supply makes more sense to me.The warning against lukewarmness remains in either case, but the subsidiary point about better to be atheist than lukewarm is open to debate, given the geographical information above.
The inclusion of the eye salve reference also backs this up as Laodicea was not only a centre of trade and banking (and special black wool) but also famed for its medicine. This salve was reported to cure certain types of eye disease and was world famous. It would seem odd to directly refer to the salve as it was in Laodicea and not be referencing the water temperature in the same way.
There, thanks.