To look back is not easy.
To look back needs at least the swiveling of the neck, hyper-extending it to maximize one's peripheral vision, to cover your back with a backward gaze. Sometimes, because it is easier, one turns his upper body by twisting his waist, shoulders and head accompanying it, to see better and more comfortably. But the easiest way to look back is to turn back, that is, to make an about-face. We do this all the time.
But why all this effort?
Initially and for the most part, I look back because I want to see. My body's design makes it impossible for me to see what is behind me. My vision of what is in front of me presents no difficulty; actually I can see far into the horizon--and everything else before it--with my penetrating gaze. Nothing escapes my field of vision; it is a matter of focusing the eyes on any object and there I catch it.
Now the problem is what is behind me. I do not have "eyes on the back of my head." This is my "blind spot." Being blind to what is behind me, I am left vulnerable. Of course, as described earlier, I can turn my head, swivel my hips, or make an about-face to overcome this blind spot. If something is going on behind me, when I hear footsteps approaching or car horns blaring at me, I turn my head so I can see. It is simply a matter changing my field of vision; now I am able to see what I could not see moments ago.
This, however, presents another dilemma for me: in turning and looking back, what was previously in front of me now becomes behind me, itself becoming my new blind spot and hence, my new vulnerability. I overcome this again by re-turning my gaze to it, or turning back again. But even if I do this incessantly, I will always fail in "covering my back" with every attempt to turn and look back. I cannot rid myself of my back. This is like trying to leave your shadow. And as long as I have a back I will always have to be vulnerable no matter what I do.
I try to look back because I am afraid of that very vulnerability. There it is: fear. Most of the time, I am afraid of what I do not see. This is why I hope to see everything--front and back. It matters not that I immediately understand (discern, know, identify) what approaches me; all I need is to see what it looks like, its speed, its apparent intention and location so I can act quickly, that is, to fight or take flight. While I am also afraid of what I do not understand, I am mostly more afraid of what I do not see. (To know is to first see; I cannot know what I do not see; "there is nothing in the understanding which did not first pass through the senses," etc.) Fear is precisely that: seeing that you cannot see. My mind cannot just bear that thought, and, unable to solve this riddle, it orders me not only to take caution but also to protect myself or just run. If I cannot cover my back completely from what I cannot see, it is better to run, hoping that my running away from it will not ultimately lead me to it. There are such a thing as traps.
I look back because I am afraid to be vulnerable. Yet does this mean that I am not vulnerable from what is before me, to what I indeed see and pretend to know? Not at all. Because I can also look back because what is behind me is what I had passed through, what is then familiar, and hence what I know--been there, done that, know that. In orienteering, I am told to retrace my steps and go back if I get lost. This means I have to remember where I passed, even leave a trail to which I can come back (e.g., Goldilocks), preoccupy myself with the thought of going back as I go forward. I then look back so I can remember. And I can only remember what I experience, what I know or understand, in short, what I see.
In contrast, what lies before me, what I do not know, calls me but also terrifies me. I hesitate to move forward (I know I have to move forward; there is no other way). But advancing means diminishing my familiarity, my understanding, my confidence. Now I am afraid--no longer with what is behind me but already with what is before me. This is why I have to look back. The angel of history, it is said, flies with its back to the future, fixing its gaze on the past.
Now everything is standing on its head. It was previously said we look back because we are afraid to be vulnerable. Now, at the same time, it is said that we look back because we are afraid of what is before us. If only I had the face of Janus my dilemma would be dissolved: for I can advance while looking after my back and at the same time keep remembering--holding on, staying--what I am afraid to leave (and forget) by my inevitable advance. But I am no mythical doorkeeper. Nonetheless, I can be a poor imitation of Janus by staying at the door, holding the key as the janitor does, neither opening it nor closing it. Or better: I can remain at the door neither entering the room nor leaving it.
Now I do not have to suffer any vulnerability by that eternally frozen door.
Before Sodom was burning with sulphurous fire, the angels told Lot to take his wife and daughters to the safety of the hills. They also ordered him to not look back. Upon arriving at the city of Zoar, Sodom and the cities of the Plain were being eaten by the tumultuous ground . Disobeying the warning of the angels, Lot's wife looked back. She was turned into a pillar of salt.
Allowed to take Eurydice out of hell, Orpheus was given simple instructions that the woman she loved will walk behind him and that he cannot look back at her. A small price to pay for a lover's life. Afraid that Eurydice was no longer behind him in their journey out of Hades, Orpheus looks back. He loses her for the second time. This time for all eternity.
An angel that looks back is no angel of God.