The Plane Crash Example

It is possible this plane will crash. Can I value the Onus of Proof Principle since it is metaphysically possible that planes crash?

[...] There you have to distinguish two different statements: it is possible metaphysically for something to happen, which does not warrant you in saying it is possible epistemologically that it will happen. Those are not the same statement. When you say that something is metaphysically possible, you are simply ascribing a certain capacity to an entity under certain circumstances. For instance, man has the possibility of walking. It is possible for him to walk, and that is not an epistemological use of the term possibility but a metaphysical one. You are describing a faculty or capacity, a potentiality of man, and it is a certainty that he has that potentiality.

When you say it is possible that so-and-so will happen, in the normal work usage of English, it indicates simply the metaphysical possibility, the capacity. But when you say it is possible that such-and-such will happen, you are giving now an assessment of evidence. You are saying there is some evidence, even if the evidence is not conclusive, that the phenomenon in question will take place. And here, you contrast possible to two other concepts: probable and certain. There’s a scale of evidential assessment. On the lowest level, when you have some evidence, you say it is possible that such-and-such will happen. As the evidence mounts, at a certain point you say it is more than possible, it is probable that such-and-such will happen. And as in when the evidence becomes conclusive so that everything points to this one conclusion and nothing points in any other direction, at that point you say it is certain.

Now, you cannot, the relevant point is, pass from a generalized statement that something is metaphysically possible—to a given kind of entity—to the epistemological conclusion that therefore you have some evidence that that possibility is being actualized. Now, contrast these two types of situations using the very example. You’re in an airplane. Of course, an airplane metaphysically has the capacity to crash. In that sense, it is possible for it to crash. After all, it’s not a feather, it has weight, it’s large, it’s up in the air, there is a law of gravity, and so on and so on. Airplanes have the metaphysical capacity of crashing. They also have the metaphysical capacity of not crashing, of landing safely without any difficulty at the airport. Both of those are metaphysical possibilities.

Now, in a given context, you’re on a particular plane. By what right do you attach yourself to “it was possible for it to crash” and then say, "therefore, it’s possible that it will crash?" You go by the actual evidence. And here, the actual evidence is much more complex, and I don’t want to take the time to go into it. But assuming you’ve got on the airplane at some place which has a decent screening system, and it’s a reputable airline, it’s a sunny day, etc., etc., etc., then you say in a normal case, it’s possible for this plane to crash. It’s also possible for it not to crash, and all the Evidence I have points to the Fact that it will land safely, and none against if that’s the case. In which case, it is invalid suddenly to say out of the blue with no basis, "maybe it will crash." On the other hand, suppose the engine starts to knock and the pilot announces we’re running out of fuel, and the clouds are closing in, and so on and so on. At a certain point, you can say, you know, it’s actually possible that this plane will crash. At that point, when you have some evidence, you are entitled to say it’s possible that it will crash. But you must have some evidence. The abstract possibility that airplanes in general can crash under some circumstances does not entitle you to say about any particular plane, in the absence of any specific evidence, that it’s possible this one will crash on this flight.