Four ingredients.
Five centuries.

What it actually said

The 1516 Bavarian ordinance permitted three ingredients in bier: barley, hops and water. Yeast is missing from the list for the straightforward reason that nobody yet knew it existed — fermentation was understood as something that simply happened to a vessel of wort left alone. When Pasteur identified yeast in the nineteenth century, it was added to the list rather than treated as a violation of it.

Why it was passed

Purity was only part of the motive, and arguably not the main one. Barring wheat and rye from brewing kept those grains in the bread supply, which kept bread cheap. The law also fixed prices and shut down the practice of stretching weak bier with whatever was to hand — herbs, soot, and in the worst cases genuinely dangerous adulterants.

What it changed

Constraint turned out to be productive. Denied additives, German brewers spent four hundred years refining malt, water chemistry, yeast strains and cold conditioning instead. The Bavarian classics on our list — Weihenstephan's wheat beers, Paulaner's lagers, Hofbräu, Weltenburger — are all products of that narrow lane being worked over and over.

Where it stands now

The Reinheitsgebot is no longer binding EU-wide law in the sweeping form it once had, and German brewers can and do make bier outside it. Most keep to it anyway, because a label saying gebraut nach dem Reinheitsgebot still means something to German drinkers.

Why we care

Because it is the same idea that runs the grill here. Fewer ingredients, treated with more attention. A bratwurst is meat, salt and regional seasoning. There is nowhere to hide in a recipe that short — which is exactly the point.