Does your sense of wonder extend no further than your eyes can see? Vision runs off into the things it sees and forgets its own seeing. Even if you could turn your eyes toward each other, Sartre thinks, you still couldn’t see yourself seeing. You are the unseen seer. Then again, there is more at work in what you see than mere images; what I see is structured by dimension, by colour, and so on. And though I can see this or that shape, one colour or another, I cannot see dimension or colour themselves. Seeing sees through these unseens. The very things that let us see are withdrawn from our seeing. Our seeing is mediated by all of these unseen factors, and not just boring formal ones like I mentioned above. Look at the things around you and think of what went into their invention, creation, and production… This occasions another kind of seeing, a new engagement with our world, and our perception… a Second Sailing…
Here’s what Socrates has to say about this in Phaedo (99d):

As I proceeded, I found my philosopher altogether forsaking mind or any other principle of order, but having recourse to air, and ether, and water, and other eccentricities. I might compare him to a person who began by maintaining generally that mind is the cause of the actions of Socrates, but who, when he endeavoured to explain the causes of my several actions in detail, went on to show that I sit here because my body is made up of bones and muscles; and the bones, as he would say, are hard and have joints which divide them, and the muscles are elastic, and they cover the bones, which have also a covering or environment of flesh and skin which contains them; and as the bones are lifted at their joints by the contraction or relaxation of the muscles, I am able to bend my limbs, and this is why I am sitting here in a curved posture–that is what he would say, and he would have a similar explanation of my talking to you, which he would attribute to sound, and air, and hearing, and he would assign ten thousand other causes of the same sort, forgetting to mention the true cause, which is, that the Athenians have thought fit to condemn me, and accordingly I have thought it better and more right to remain here and undergo my sentence; for I am inclined to think that these muscles and bones of mine would have gone off long ago to Megara or Boeotia–by the dog they would, if they had been moved only by their own idea of what was best, and if I had not chosen the better and nobler part, instead of playing truant and running away, of enduring any punishment which the state inflicts. There is surely a strange confusion of causes and conditions in all this. It may be said, indeed, that without bones and muscles and the other parts of the body I cannot execute my purposes. But to say that I do as I do because of them, and that this is the way in which mind acts, and not from the choice of the best, is a very careless and idle mode of speaking. I wonder that they cannot distinguish the cause from the condition, which the many, feeling about in the dark, are always mistaking and misnaming. And thus one man makes a vortex all round and steadies the earth by the heaven; another gives the air as a support to the earth, which is a sort of broad trough. Any power which in arranging them as they are arranges them for the best never enters into their minds; and instead of finding any superior strength in it, they rather expect to discover another Atlas of the world who is stronger and more everlasting and more containing than the good;–of the obligatory and containing power of the good they think nothing; and yet this is the principle which I would fain learn if anyone would teach me. But as I have failed either to discover myself, or to learn of anyone else, the nature of the best, I will exhibit to you, if you like, what I have found to be (a second sailing), the second best mode of enquiring into the cause.
I should very much like to hear, he replied.
Socrates proceeded:–I thought that as I had failed in the contemplation of true existence, I ought to be careful that I did not lose the eye of my soul; as people may injure their bodily eye by observing and gazing on the sun during an eclipse, unless they take the precaution of only looking at the image reflected in the water, or in some similar medium. So in my own case, I was afraid that my soul might be blinded altogether if I looked at things with my eyes or tried to apprehend them by the help of the senses. And I thought that I had better have recourse to the world of mind and seek there the truth of existence. I dare say that the simile is not perfect–for I am very far from admitting that he who contemplates existences through the medium of thought, sees them only ‘through a glass darkly,’ any more than he who considers them in action and operation. However, this was the method which I adopted: I first assumed some principle which I judged to be the strongest, and then I affirmed as true whatever seemed to agree with this, whether relating to the cause or to anything else; and that which disagreed I regarded as untrue. But I should like to explain my meaning more clearly, as I do not think that you as yet understand me.