  It is noteworthy that Aristotle's theory does not mark off those vital functions that are mental by relating them to the soul in some special way that differs from and goes beyond the way in which vital functions in general are so related. It is certainly not part of Aristotle's theory that the soul is specially and directly responsible for mental functions by performing them on its own, whereas it is less directly responsible for the performance by the living organism of other vital functions such as growth. As this aspect of his theory suggests, Aristotle is confident that once one has a proper understanding of how to explain natural phenomena in general, there is no reason to suppose that mental functions like perception, desire and at least some forms of thinking cannot be explained simply by appealing to the principles in terms of which natural phenomena in general are properly understood and explained (cf. Frede 1992, 97).