Sometimes the subject of a sentence is best left unstated, making it impersonal. One way of doing this is to use a passive construction beginning with the word
it.
| People may subsequently prove that such transitions are possible.
Someone may subsequently prove that such transitions are possible. |
| It may subsequently be proven that such transitions are possible. |
Nevertheless, if when revising your draft you find many sentences with this structure, consider whether there are better options that can accurately specify the subject using the active voice.