Wednesday, August 17, 2005

Simultaneous vs. Instantaneous

It is astonishing to me how many people confuse 'simultaneous' with 'instantaneous'. But the two are nothing alike.

(1) 'Instantaneous' means 'occurring in an instant' or 'occurring at an instant'; 'simultaneous' means 'occurring at the same time'.

(2) Instantaneity is not a relation; event E can be instantaneous in itself simply by occurring in an instant (assuming that it's possible for an event to occur in an instant). Simultaneity, however, is a relation: A can't be simultaneous on its own; it has to be simultaneous with something. A and B, however, can be simultaneous.

(3) Events that are simultaneous can last a short time or a long time. For that matter, there's nothing to prevent two events from being simultaneous for all time. This is obviously not so with instantaneous.

I notice the confusion a lot when people are talking about simultaneous causation; they are constantly assuming that 'simultaneous causation' means 'instantaneous causation'. But, naturally, this is not so.