Actually, we may not have any clear artifactual kinds.
Cattle are the artifactual kind.
I tend to be in agreement. Focusing too closely on the term 'vague', from Philip's original posting, can be a red herring. Vague' is an adjective, different things might be called vague for different reasons and in different ways, so there is no absolute sense of the term. I prefer simpler examples to start with. Putting the same volume of rocks in a quarry and you have something so insignifigant that if you take your eyes off it you probably won't be able to find it again.