Can we say, with respect to reality, that "I AM not just What I AM"? That, aside from things actually existing or having been in the past, the real possibilities too must be treated as part of reality for all intents and purposes -- for example, to exert free will as a conscious choice?
Does modern philosophy has the concept of "real possibility"?
Also, following up on comments, "How do we know something was, in fact, possible since it did not happen?"
There are two ways to word the answer. Using modern terms, this particular superpower -- knowing what's possible -- is something we have evolved as humans. No other species on the planet have it. It was the purpose of our genus' evolution over the course of the last 5 million years, and it makes us who we are -- for better or worse.
At the heart of our humanity lies the highly specialized computing hardware of our prefrontal cortex. The rest of the brain we have inherited from our animal ancestors as-is, and it is a good ole Neural Network supercomputer. However, the prefrontal cortex resembles traditional architecture: a rather basic arithmetic/logic unit paired with a much more capable graphics processor. It's good for imagining (or daydreaming) virtual realities -- from pure fantasies to realistic real-world simulations. The latter could mean seeing those "real possibilities", given that the person possesses the necessary skills and their knowledge of the real world is reasonably complete and accurate... None of which we are, sadly, born with (so much for intelligent design).
Instead, we are simply given extra 4-5 years of childhood to allow for the essential skills and knowledge to be shared with us by supportive adults and older children. And they have been, for most of our history, teaching that art to every child -- the art of being your rational, conscious Self. Back then, we didn't know about evolution, we didn't know how exactly it works, but we knew that every person -- their Self, their human soul -- is made in the Ultimate Reality's own image, and that's how they can know the world!
But it is no coincidence that our prefrontal cortex is hardwired for 3-dimensional space, with the rules of inference, logic, and reason that we find behind every act of creation, the rules that make the world go round. We end up this way because we have evolved being a part of this world, this reality:
"Through [the Logos] all things were made; without it, nothing was made that has been made."
In other words, as children, we should have been taught to use our rational minds properly. However, for reasons too sad to mention we weren't... so we aren't!
"... In it was life, and the life was the light of men. And the light in darkness shineth; and the darkness comprehended it not."