3 “Another said, I have bought five pairs of oxen.” Would it not have been enough, “I have bought oxen”? Something beyond doubt there is, which by its very obscurity challenges us to seek out, and understand; and in that it is shut, He exhorts us to knock. The five pairs of oxen are the senses of this body. There are numbered five senses of this body, as is known to all; and they who, it may be, do not consider it, will doubtless perceive it on being reminded of it.
There are then found to be five senses of this body. In the eyes is the sight, the hearing in the ears, the smell in the nose, the taste in the mouth, the touch in all the members. We have perception of white and black, and things coloured in whatever way, light and dark, by the sight. Harsh and musical sounds, we have perception of by the hearing. Of sweet and offensive smells, we have perception by the smell. Of things sweet and bitter by the taste. Of things hard and soft, smooth and rough, warm and cold, heavy and light, by the touch.
They are five, and they are pairs. Now that they are pairs, is seen most easily in the case of the three first senses. There are two eyes, two ears, two nostrils; see three pairs. In the mouth, that is in the sense of taste, a certain doubling is found, because nothing affects the taste, unless it is touched by the tongue and the palate. The pleasure of the flesh which pertains to the touch, has this doubling in a less obvious way. For there is both an outer and an inner touch.
And so it too is double. Why are they called pairs of oxen? Because by these senses of the body, earthly things are sought for. For oxen turn up the earth. So there are men far off from faith, given up to earthly things, occupied in the things of the flesh; who will not believe anything but what they attain to by the five senses of their body. In those five senses do they lay down for themselves the rules of their whole will. “I will not believe,” says one, “anything but what I see.
See, here is what I know, and am sure of. Such a thing is white, or black, or round, or square, or coloured so and so; this I know, am sensible of, have a hold of; nature itself teaches it me. I am not forced to believe what you cannot show me. Or it is a voice: I perceive that it is a voice; it sings well, it sings ill, it is sweet, it is harsh. I know, I know this, it has come to me. There is a good or a bad smell: I know, I perceive it. This is sweet, this is bitter; this is salt, this insipid. I know not what you would tell me more. By the touch I know what is hard, what is soft; what is smooth, what is rough; what is warm, and what cold. What more would you show me?”
Source: Sermons on Selected Lessons of the New Testament (New Advent)