I've found that asking non-engineers to explain to me how to make a cup of tea can be helpful in explaining why software development is so complex.

They'll usually say something like "boil the kettle, pour the water in the cup and wait a few minutes"

So then you go in and probe all the requirements and edge cases:

- what if there's no water in the kettle?

- what if there's no power to the kettle?

- what if we're out of tea bags?

- how do I know when the kettle is boiled?

- can I put the tea bag in the cup while the kettle boils, or do I need to wait for the kettle to be ready first?

- what size cup do I need?

- how do I remove the tea bag?

- what if there are no clean spoons?