Realist philosophy starts with what we observe in the world, while analytic philosophy starts with a thought problem and reasons to what is true in the world. Most modern thinking is analytic, which is one reason philosophy is not taken more seriously in our day. Analytic methods are so prevalent that many know no other way of thinking and do not realize what they are doing.
Aristotle said this:
“The fact of the being of a man carries with it the truth of the proposition that he is, and the implication is reciprocal: for if a man is, the proposition wherein we allege that he is true, and conversely, if the proposition wherein we allege that he is true, then he is. The true proposition, however, is in no way the cause of the being of the man, but the fact of the man’s being does seem somehow to be the cause of the truth of the proposition, for the truth or falsity of the proposition depends on the fact of the man’s being or not being”. (The Categories, 12.14b15)
Thus it is only reasonable to take what is real and base our knowledge there, rather than to start with our reason and conclude about what is real. We therefore, like Aquinas, take the Bible and our knowledge of the world and base it on the reality that is external to our minds. We ought not start with pure reason and make conclusions about the world. Like Plato and Descartes, if we start in the mind, we are forever locked in our mind, never being able to reach the real world.
What all this means is that we do not start with thought problems based upon what might be in all possible worlds or in what might occur in counterfactuals. Instead, with the Bible we start with special revelation, and with the world we start with observations of the universe, knowing that the world exists but is contingent, and effects have causes, etc.