* I do not understand the addition of or in his translation.
I think the or
is just the translator using poetic license. The phrase when translated into English is weak.
I translate the whole thing as something literally like:
there are many mortals that come to know by seeing
but there is no foreteller that knows before (it happens) of the future, what (action) might happened.
I would probably pretty it up by saying:
There are many men that know by sight but no one can see what might happen in the future.
just my $.02