A discipline being superfluous? I heard for the second time today that a discipline is "superfluous". This comment was made by a young assistant professor, who does not do research in this discipline. Just to be fair to the commenter, that was not a serious comment, but just a casual remark.

However, I think deep in his mind he believes that this discipline is "superfluous". And deep in my mind I have the same doubt from time to time. Can a discipline be superfluous? How do you know whether a discipline is worth researching or not?

PS: In this case this discipline is HCI (human computer interaction), but you could replace it with any other discipline.
Superfluous usually means unnecessary. So the person is claiming that a discipline is unnecessary. Presumably, this is a claim that can be investigated further: does research in that discipline have any kind of external impact ? does it affect other related disciplines ? Is there at least a path from the questions being asked to some future impact ? 

In fact these are all good questions to ask about any discipline, whether it's deemed superfluous or not. And these are good questions to ask about one's own research in a discipline. 

p.s While this is off topic, there's a common feeling among CS folks that HCI is either fluffy or superfluous. All of these people are also forbidden from using a Kinect, any video game console, a tablet interface, or even a smartphone.