And what is the cause of their not wanting to bring this attention to bear, unless it is that their wills are disturbed and inconstant, thereby incessantly agitating their understanding, so that the understanding does not have the leisure to perceive distinctly even those ideas that are most present to it, such as those of thought and extension: just as a man excited by some passion, who constantly glances in all directions, usually does not discern those objects closest to him and most easily perceived.