  The affinity argument is supposed to show not only that the soul is most like intelligible, imperishable being, but also that it is most akin to it. Socrates argues that the soul is like intelligible being on the grounds that it is not visible and, in general, not perceptible (anyhow to humans, as Cebes adds at 79b), and that it shares its natural function with the divine, namely to rule and lead (the body in the one case, mortals in the other). There is a separate argument for the kinship of the soul with intelligible being. When the soul makes use of the senses and attends to perceptibles, “it strays and is confused and dizzy, as if it were drunk” (79c).  By contrast, when it remains “itself by itself” and investigates intelligibles, its straying comes to an end, and it achieves stability and wisdom. It is not just that the soul is in one state or another depending on which kind of object it is attending to, in such a way that its state somehow corresponds to the character of the object attended to. That would not by itself show that the soul is more akin to the one domain rather than the other (this is the point of Bostock's criticism, Bostock 1986, 119). To understand the argument properly, it is crucial to note that when the soul attends to perceptibles, it is negatively affected in such a way that its functioning is at least temporarily reduced or impaired (“dizzy, as if drunk”), whereas there is no such interference when it attends to intelligibles (cf. Socrates' fear, at 99e, that by studying things by way of the senses he might blind his soul). The claim that the soul is akin to intelligible reality thus rests, at least in part, on the view that intelligible reality is especially suited to the soul, as providing it with a domain of objects in relation to which, and only in relation to which, it can function without inhibition and interference and fully in accordance with its own nature, so as to achieve its most completely developed and optimal state, wisdom.