Isaiah received a command to put a watchman on duty to report on what he saw concerning Babylon's downfall. Isaiah was not to station a literal watchman on some lookout point; placing the seer was a visionary way of stating that he would be informed of what was to occur. Furthermore, Babylon did not fall until many years later. It is quite possible that Isaiah himself was this watchman, or that he, in the vision, was stationing a second person to represent him. He saw the happenings in Babylon in his mind's eye, through the visions given to him by God. Isaiah also emphasized that these words came from God and not from himself.
It is also not true, as some think, that Isaiah was acting in a kind of prophetic frenzy in which he could perform actions wherein his spirit separated from his body and in which he was unconscious of the real world. On the contrary, Isaiah acted as a consciously aware person throughout the vision. There is no question of superstition or magic.
6 For thus the Lord said to me: “Go, set a watchman; let him announce what he sees.