Sidetracking, but thinking of Amos' line (I'm not implying a set here just descision making), it can be interesting to say give instructions make a cup of tea. I mean for example that could include a loop something like "while water is not hot enough continue to apply heat". There is much we do naturally but take for granted. In that case we would all say wait till the kettle has boiled.

As for threads and sets, every post in this thread belongs to a group of posts but are only posts with an ID 679988. Few of us would ever think of the (say, pretty sure it is SQL Server here) SQL behind that when reading.

We are quite remarkable at using processes subconsciouly.