Critical Thinking Toolkit: Possible v.s Plausible

In our common experience, there are a plethora of alternative explanations of the realities we see around us. Some of these are highly likely, some fairly likely, some moderately likely, some that are reasonable but not strictly ‘likely’, and some that are extremely unlikely. There are a variety of situations that we might find ourselves in when we are evaluating options of how to understand the world around us. We must be careful that we accurately assess and consider these distinctions in alternatives that are presented to us – and we should attempt as best as is possible to give alternative perspectives some benefit of the doubt and not reject them outright as impossible.

The distinction I want to deal with here is fairly easy to explain, although the implications are often missed unless very carefully thought out. Here is the idea. Suppose that you are talking to someone you disagree with, and they make (as far as you can tell) a really good point. Generally, changing your mind on a whim is ill-advised, since changing your mind on anything important enough to be worthy of a careful debate will have a lot of implications to how we live our lives. In other words, the more important something is, the more careful we ought to be in changing our minds. So, if someone presents to us a perspective that contradicts our own, we need to try our best to objectively evaluate how reasonable it is. Similarly, we have to evaluate how reasonable our responses to other people’s criticisms are.

Let me give an extreme example. Suppose that Alice and Bob are having a discussion about philosophy, and that Alice tells Bob that she believes that Bob does not actually exist, but that she is actually the only person that exists and that all other people and events are nothing more than her imagination keeping her occupied (this roughly corresponds to a philosophical view called solipsism). From Bob’s perspective, since I know that I exist, Alice must be incorrect. But from Alice’s perspective, it is at least possible (by restricting ourselves to the laws of logic) that Bob doesn’t exist. Bob will naturally respond to Alice’s statement by trying to convince Alice that he actually does exist. In this situation, Alice has two possible viewpoints being presented to her:

(1) Bob is an illusion created by my subconscious mind.

(2) Bob actually exists as an individual separate from my own mind.

Alice is faced with asking herself which of these alternatives is actually correct. As I have already laid out, both of these alternatives are possible – neither of these statements are on the same level of absurdity as 1 + 1 = 3. But I think that very nearly all of my readers would agree that option (2) is much more reasonable and likely than option (1). Option (1) seems like an unintuitive invention, and option (2) corresponds to how we normally think about the world. Our daily experience of the world seems on an intuitive level to fit into (2) better than (1). For instance, if (1) were true, then why would our brain give us illusions of things like pain and sadness? If (2) were true, it makes sense that someone who exists separately from ourselves might occasionally cause us pain or sadness.

In summary, even though both (1) and (2) are possible, only (2) is plausible. For anyone who hasn’t heard the word before, plausible means something like ‘at least reasonably likely to be true,’ whereas all that possible means is that no basic laws of logic are violated. In light of this distinction, the following statement is something that all of us have to keep in mind:

If someone who disagrees with you presents a plausible alternative, you cannot give a merely possible response. Your response to someone else’s criticism should reach the same “level of likelihood” as the criticism leveled against you.

It is true that most of the time, there is some level of subjectivity to the assessment of likelihood. It is even quite possible that someone reading this is inclined to think that solipsism is plausible. If so, then I don’t deny that you believe that solipsism is plausible – but I very strongly disagree. To me, solipsism is only a tiny bit removed from the claim that 1 + 1 = 3. But I’m also quite happy to dialogue with a person who disagrees with me, because I believe strongly that we ought to do our best to remove ourselves from our own perspectives when we have conversations like this, and I am open to being corrected if a solipsist can bring me better evidence for solipsism than I have for the contrary (although to be frank, I can’t even imagine what that evidence would look like). But if a solipsist brings to me a possible reason to reject my current beliefs, that is not good enough for me.

Similarly, I am thoroughly convinced that God supernaturally rose Jesus Christ from the dead on the third day after his crucifixion. If someone brings me some other explanation for the historical details we know about the emergence of the Christian church in the years after Jesus’ death, the explanation being merely possible is not good enough for me to doubt my faith in Christ. I would need to be given a synopsis of all relevant pieces of information that is at least as convincing as the view that Jesus actually did rise from the dead. And I fully expect that any Muslim speaking with me would require that I show them something at least as convincing as the evidence they have for their Islamic faith, and I expect that an atheist would require that I bring forth a totally of evidence that is at least as strong as the evidence they have for atheism.

All of this discussion is important, and each of us should consider our own views about the world and whether we actually have convincing evidence for what we believe that could convince people who disagree with us that we have a plausible interpretation of the world. At the end of the day, we all must remember that we cannot allow ourselves to reject what other people believe just because we can invent some alternative explanation – we must put our own explanations into a skeptical light and do our best to determine how reasonable our own explanations are and how reasonable the explanations by people who disagree with us are.

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