I have several midi controllers. They are not instruments. I have many instruments (including vst's) that have controllers on them. Apart from my old rackmount Korg Wavestation a/d I have several instruments without controllers.

The old concept of an instrument does not map well to electronic music equipment- perhaps it would make sense to say that the combination of the input device that interacts with your body, and the computer or synthesizer are together a single instrument? In the same way that all of the different parts of a guitar are one instrument.