I am a fan of clarity, preferably in a concise manner but I suspect that this write-up won’t be particularly so. These three common terms (Possible, Plausible, and Probable) are sometimes used interchangeably, and in the context of religious discussions they are used with intention of arguing for or against a god. This makes it imperative that these terms be used appropriately and clearly, as well as their antonyms (Impossible, Implausible, and Improbable).
I’ll use as an example, William Lane Craig’s premise that “The very possibility of God’s existence implies that God exists.” (I took this quote from this essay here:
http://www.reasonablefaith.org/popular-a...od-exist). What is meant by possible in this context? He goes on to say “In order to understand this argument, you need to understand what philosophers mean by ‘possible worlds’. A possible world is just a way the world might have been. It is a description of a possible reality. So a possible world is not a planet or a universe or any kind of concrete object, it is a world-description. The actual world is the description that is true. Other possible worlds are descriptions that are not in fact true but which might have been true. To say that something exists in some possible world is to say that there is some consistent description of reality which includes that entity. To say that something exists in every possible world means that no matter which description is true, that entity will be included in the description. For example, unicorns do not in fact exist, but there are some possible worlds in which unicorns exist. On the other hand, many mathematicians think that numbers exist in every possible world.”
But is that what the word “possible” really means? Well, yes and no. Possible is a word that is intended to mean that something may or may not exist (or may or may not have occurred) based on our understanding of how things work. The critical part of this is that there must be some sort of evidence to point to in order to say that something/someone/some event, is possible. WLC even gets close to this in his unicorn example. We know, based on the study of evolution and biology, that Unicorns are not possible beings in our universe because no evidence exists to show their possible existence and evidence does exist to show how the lineage of horses includes no characteristics that would produce the anatomical features of a unicorn. So WLC correctly asserts that unicorns are not possible in this universe, but is it true that they are possible in other universes? No, it isn’t. For a couple of reasons: 1) we don’t have any evidence to show that other universes exist and 2) even if other universes do exist, we don’t know anything about them, we can only hypothesize what they could be like. In short, we don’t know anything about their actual possibilities or the actual possibilities of things existing/occurring within them. I realize that the math associated with quantum mechanics and the multiverse hypothesis assert some interesting things that might be true, but these are not evidence that these things that might be true are realistic or possible. For instance, they may be telling us more about human imagination than external realities.
Okay, so the take home point for the word “possible” is that in order to assert that something is possible to exist or have occurred, you need some piece of evidence that it exists in order to point to it and say it is a possible explanation. An example would be bolide impact killing off the dinosaurs. Is that possible? We find craters on Earth showing that we have been hit by large bolides before, making it entirely possible that a large one could strike the Earth. Secondly, we know what the effects of an impact would be and what the consequences of large amounts of particulate matter are. We can look at the craters and calculate how large the objects were and how much ejecta they produced and calculate the atmospheric effects using observations of similar events (like large volcanic eruptions). So, is it possible that a large bolide impact could have resulted in the extinction of the dinosaurs? Yes, because the Earth can and has been hit before and the consequences of a large enough impact would result in widespread “nuclear” winter-like conditions that would generate the ecosystem stress to drive extinctions.
Let’s use an alternative explanation; is it possible that sentient aliens intentionally killed off the dinosaurs? We have no evidence that advanced alien civilizations exist or have visited Earth. So no, it is not possible that aliens killed the dinosaurs.
Why go through all of this? It’s because of the other two words I highlight: Plausible and Probable. Plausibility is intended to say whether or not a possible thing or scenario is or isn’t likely to have existed or occurred. It isn’t a calculation of the odds, it is a qualitative evaluation of what the possible thing/event’s effects would be and whether or not the evidence substantiates it as a likely candidate. So, let’s ask another question of the dinosaur extinction: is it plausible that competition from mammals drove them to extinction? This is a possibility given that 1) mammals were around at the time, 2) competition can drive extinction, and 3) the mammals radiated after the dinosaurs were gone. So we know that this is possible, but does the evidence logically conclude this? No, because this explanation does not sufficiently explain the extinction of marine organisms at the same time, it also does not provide an explanation for the evidence of the bolide impact. Therefore the plausibility of this scenario is considered very low or effectively implausible.
The last term is probability, which is now a calculation of the odds associated with plausible things (events or existence of things). Probability means you actually have a method for calculating the odds of something happening or something having existed. But this can get tricky.
For instance, what is the probability of winning the lottery? Those odds can be calculated based on the frequency at which winners are drawn, how many people play, and how many numbers you have to select in order to win. But once you play, you either win (probability of 1, or 100%, means you win) or you lose (0 or 0%). So calculating the probabilities before hand does not predict what will actually happen, it can’t tell me the truth because it can only tell me what the odds are of a plausible scenario are. So, could we calculate the probability of a unicorn existing? No, because we can’t conclude that one is plausible because we can’t conclude that they are possible.
And this is the big take home point. You can’t accurately or reliably assess the probability of something that can’t be shown to be plausible and you can’t assess the plausibility or probability of something if you can’t demonstrate it is first possible. And in order to show something is possible, you need evidence to corroborate its existence in some way. You need to show that it occurs in nature. You need to show that it is present in some way in the universe.
So, when people assert the probability of a god existing, they are starting off with the assumption that a god is possible, but that is not a corroborated claim. That makes any attempt at calculating the odds or the plausibility, pointless and useless.
This is also why Intelligent Design/Creationism are not taken seriously outside of religion. It is because the possibility of an intelligent designer has never been shown. That makes all of the “evidence” of intelligent design moot because it cannot be shown to logically connect to the intelligent designer because no evidence of an intelligent designer exists. This results in circular arguments where the “evidence” of intelligent design is then used as evidence of the designer, but that can’t be logically concluded because you can’t conclude it is evidence of intelligent design without showing that the intelligent designer is real.
