Now, I know what you're thinking.
Being salt of the earth - and being light to the world. Aren't they, very much, opposites?
Salt - a mineral so useful that people could be paid in it. When pure it's shiny, white, bright. When bought by somebody who thinks it's more "organic", "natural" to buy as sea salt - what do we think we're doing when we buy sea salt to put on our chips? It's not like it's been organically raised in free-range salt farms, where the salt can live a happy, natural salty life. Skipping around the fields in its salty way, grazing on free-range sodium. No. Or even, Na. Basically, sea salt is salt with dirt in it - because the sea is not pure and unadulterated. It's got other salts, and fish droppings.
In Jesus's time, I reckon the salt would have come from salt pans - areas where they let the sea in, then evaporate it off in the Mediterranean sun. In this country, most salt is mineral salt. It's mined under Cheshire, where it forms quite literally a rock formation under the ground. And the air in the tunnels of salt mines is so pure, so dry, that the tunnels are used for document storage - because it's too dry for microorganisms to grow.
But how can salt be kept pure, and salty? Or, to put it another way - what makes it lose its saltiness? Well, salt has a property called "deliquescence". It absorbs moisture, it gets clumpy. That's why salt in shops also contains sodium or potassium hexocyanoferrate - to stop it clogging up. So if salt gets damp, it's not so useful as salt. If it gets grubby, it's not so salty, because there's all sorts of stuff going on.
I remember doing an experiment, long and merry enough now, in the old Dyson Perrins lab in Oxford. And being a very bad chemist, I didn't make enough of the product I was making. My yield - we're very keen on yields, in the chemical community - was not good. What to do? I wasn't going to do the experiment again. I had a busy life. But I wasn't going to hand in my test tube, with just 20% or so yield.
So I took an executive decision. The thing about labs is, there's always some kind of kind of chemical crud laying around on the benches. So I scraped some of that off with a spatula, shoved it in, pushed the yield up to 50% or so, and went off to see the supervisor to get my experiment signed off.
But it wasn't the thing I was trying to make, was it? It was half made up of random chemicals, bits of lab bench varnish - not the thing I wanted at all. The melting point was all wrong. The next step in the experiment was to use that chemical to make another thing. And I had a product that was largely varnish. It did not augur well for the future.
And so, to keep the right chemical composition, to keep our salt pure - salty - it's clear what we have to do, isn't it? We have to flee away from the things that contaminate us - from the evil in the world. Like the communities that lived around the Dead Sea - with all that salt - in Jesus's time. Staying away from the World. Staying away from the compromises. Not getting grubby, not living lives that were clogged - there's still communities out there now, trying to do the same thing.
Or the 21st Century equivalent maybe? Only listening to Christian music. Only having Christian friends. Only going to Church activities - filling your life with church meetings and "socials". As Steve Taylor once said, only drinking milk from Christian cows.
It's tempting. And it's been done. And it's right, that there are things in the modern world - behaviours and attitudes - that we don't want to pick up. And if you're thinking I mean certain lifestyle choices and sexual attitudes - well, I don't really. I was thinking of selfishness, judgmentalism, self-righteousness, grudges and pride. We should certainly want to run away from the world to get rid of them, shouldn't we?
After all , we don't get those in the Church, do we?
But we have the call to be salt - shiny, pure, clean, uncontaminated, best kept protected in a plastic bottle - alongside the call to be light - shiny, pure, and shed over dirty and clean things alike. If you're light to the world - shining out, not protected under a bowl - ten you can't hide away. In fact, if you put a candle, tea light, oil lamp or other fire-based light source under a bowl, you're running the risk of putting it out, through lack of air.
If the Church in this area disappeared - would anybody notice? Would it mean a vital spark had gone, a precious light that had gone out, a vision that others could catch - was no longer available?
Or would it be more like when the bingo hall went - just another leisure alternative that lost its market? Just a slight sadness that something had gone, combined with the reflection that instead of evensong - or the evening bingo sitting - or the Junior Temperance League - or roller skating, or whatever it might be, now you'll have to sit at home and watch Downton Abbey? Is that all it would be?
So what are Christians known for - squabbles over robes, rules about gay priests, where people get to sit, the precise wording of liturgy - all those other attempts to stay "pure", like a shiny kitchen condiment in our glass cruet?
Or street pastors, food banks, genuine day-to-day living alongside people in need - fund raising for schools and hospitals and charities just as much as for the tiles on the vestry roof?
I think I may have set a false dichotomy. You see, salt may be pure, and shiny and white and crystalline when it's sat in its box or bottle. But it's not much use on the kitchen shelf.
Salt is most salty, most tasty and useful, when it's poured out. It's still salty when you're gargling with salt water - when it's used to dab on a sound - and don't we know it. It's still salty when it's poured out on chips, it's still salty when it makes corned beef. Maybe Jesus was using the same story twice. The way to let salt get unsalty is to leave it on the shelf to get damp and caked and grubby. And then it's not so useful - you may as well use it to pour out on the drive, if we ever get a frost this year. But poured out, used, made visible and tasteable, salt and light are things that change, that reveal new things, that make a difference to the world in which we live.