[OJFord]

Sure, and dust, and any other spores or pollutants in the air, I didn't mean to provide a pure and complete list, I just meant that it's not some magic yeastless concoction that also happens to make bread rise. It's still yeast doing the work, it's just naturally occurring, rather than added from a packet of commercially grown and sold yeast.

[quietbritishjim]

Right, but that article claims that lactobacilli are critical to make the bread actually taste like sourdough at the end, whereas presumably dust isn't.

I did realise your main point is that it does include yeast, and I agree with that.

[OJFord]

Oh yeah, absolutely, I just meant that all (leavened) breads contain yeast, I suppose it's a defining feature; so it's not 'yeast vs. starter', it's 'yeast from a packet vs. yeast from the air'.