Minefields are areas filled with randomly scattered explosives: one can be pretty sure that some of them, some time, will explode -but one can't say with any degree of certainty which ones and when.

Few of us would hire someone to repair their home without knowing how much it will cost and how long it will take at least with some degree of certainty.

So it has been proposed that blue-eyed men prefer blue-eyed women as mates because they have some degree of certainty over fatherhood.