Why Plato mentions only being visible and tangible

The whole account will unfold these things as it proceeds. Right now let us just say that since the cosmos is extended and grasped by sense perception, it is known through both sight and touch, being visible in as much as it is through and through suffused with light, while being tangible in as much as it is solid. For it is sufficient for Plato to embrace all the objects of sense (aisthêta) just by mentioning these two senses. For when viewed in relation to the four elements that always exist in the cosmos, these things – the visible and the tangible – are opposites. This is because they are furthest apart and under the same genus. Both of them are kinds of things that are sensed and this is their common genus, but they are also very far apart, presuming that the one is a sense object that involves no medium while the other does.

But if we were to investigate the contraries among the elements in as much as they are subject to change, we would not say that the contraries are fire and earth, but we would rather say fire and water are contraries. For water in particular quenches fire. And each of these accounts is true. For it is common to both accounts to establish the contrariety in the extremes and in this respect the choices [about contraries] are in agreement: qua sensibles, earth is contrary to fire, but qua things that undergo change, water is contrary to fire. That is why Plato has set out the visible as something contrary to the tangible, taking the elements qua sensibles and not yet considering them qua things that undergo change, for in this way water is more opposed to fire than earth. And so the account is not incomplete as Theophrastus thinks. He raises the following puzzle: ‘why ever did Plato say that visibility was the defining feature (idion) of fire and tangibility [the defining feature] of earth, yet say nothing of the remaining elements?’ In response to him we say that we actually see the cosmos and touch it, but we don't in any way taste it or hear it or smell it. In addition, the actual cosmos itself is visible and tangible to itself.