Why the tin is always full

If you recognised that Thursday, you may have the familiar feeling that you're weak. I don't think so, and I'd like to start with how heavily the odds are stacked.

People like sweetness from birth. Newborn babies respond to a sweet taste with what looks very like pleasure, long before anyone has taught them anything. For most of human history sweetness was rare and marked food that was safe and rich in energy, such as ripe fruit and honey. A liking for it was useful. You've inherited that liking, and it now operates in a world where sweetness is the cheapest and most available taste there is.

It is everywhere. There are sweets at the till and the petrol station, pastries in the meeting and a bowl of something on reception, and the coffee shop has a cake cabinet at eye level. A packet of biscuits costs less than a pound. The NHS says that the sugars most adults and children in the UK eat too much of are what it calls free sugars, which means sugar added to food and drink, along with the sugar in honey, syrups and fruit juice. If you eat more of it than is good for you, that's the national condition.

Then there's what you were taught. Think about what sweets meant when you were small. They were what you got for being good at the dentist, for finishing your greens, for a good school report. When you fell over and cried, somebody gave you a biscuit. Sweets were handed out at birthdays, Christmas and Easter, which were the best days of the year. Nobody meant any harm by this. But by the age of seven you'd had hundreds of lessons in a simple code, in which sweet things mean you've done well, or that things will be all right, or that it's a special day. You still read that code fluently.

In Britain we've built a daily ritual on it. A cup of tea comes with a biscuit. Elevenses, the tea break, a sit-down with a brew and something from the tin are small, decent institutions, and there's friendship and rest bound up in them.

So the three jobs aren't arbitrary. Each one grows out of something real.

Reward. You finished a hard thing and you want it marked. Most work ends with nothing at all. You press send and the next task is already waiting. A biscuit is a way of saying to yourself that something was achieved.

Pick-me-up. You're flagging in the middle of the afternoon and there are two hours still to go. You need to function, and sugar is known to be quick energy. Everyone says so.

Comfort. You're upset and nobody's there, or what's wrong can't be fixed tonight. Something sweet is kind, and it's immediately available, and it doesn't ask anything of you.

Underneath these are needs nobody should be ashamed of. You want your efforts acknowledged, you want energy when you're tired, and you want soothing when you're hurt. The question for the next several chapters is whether the tin meets those needs. I'll argue that it doesn't really meet any of them, and that it stops you looking for whatever would.