My suggestion is that Aquinas himself accounts for the cognitive differences between the senses in terms of the relative proportion of spiritual to natural immutation permitted by the sensory organs.
This process is achieved through what Aquinas calls a `spiritual immutation':
Now, immutation is of two kinds, one natural, the other spiritual.
immutation takes place when the form of that which causes the immutation is
form of what causes the immutation is received, according to a spiritual mode
spiritual immutation is required, whereby an intention of the sensible form is
So, in the case of natural immutation the body affected itself undergoes a change in quality whereas with spiritual immutation the affected body does not itself undergo any change but does take in the form of the object perceived.
On the part of the object, we find local natural immutation in sound, which is
We find natural immutation by alteration in odor, which is the object of
The sense of sight, Aquinas claims, involves no natural immutation since the eye itself is not coloured when it perceives a coloured object and the air through which the light reflecting the object moves is also unchanged, since it is transparent.
Now, the sight, which is without natural immutation either in its organ or in its