Critical Thinking Toolkit: A Priori Assumptions

This is one of the most important – perhaps the most important – of the many tools in the “critical thinking toolkit.” I don’t say this because I like this topic most among the topics I want to write about – although I do enjoy this topic a lot. The main reason I think this is so important is because it is always relevant to all discussion involving two people who disagree, and I see this issue underlying almost all of “public ideological battles” today. Perhaps I am exaggerating slight here… but only slightly. The topic I want to discuss here rears its head in pretty much every discussion.

There is a need to clarify some terminology, because the terminology that is normally used here is actually Latin. The term is a priori. I think in order to most clearly define this terminology, it is helpful to introduce the terminology that is usually used as its opposite – a posteriori. For readers who don’t speak Latin (which includes myself), in order to compare the two, the phrases a priori and a posteriori can be translated basically as from the earlier and from the later. In order to understand what we mean, we must answer “Earlier or later than what”?

The answer is this – earlier or later than experience/observation. In light of this, what I mean by a priori means ‘before experience’ and a posteriori means ‘prior to experience.’ To understand what I mean, let’s give an example. Consider the statement, “Because I am 10 years old, I am more than 5 years old.” Now, numbers can be defined without reference to our personal experience of the world, so you can affirm the previous statement without referring to your own experience of the world. It is true that you can experience that 10 is more than 5, but you don’t have to experience it in order to know that it is true. This kind of situation is what is meant by a priori.

On the other hand, consider the statement “I am 10 years old.” In order to know whether this is true or not, you need some experience. You need to know, for example, who is speaking. You also need to know when they were born. Those are not aspects of reality you can understand without drawing from experiential reality. This is what is meant by a posteriori.

This is the sort of thing that is mean by a priori and a posteriori. More specifically, if you are in a debate with a person, an a priori assumption is something that you hold to be true that you hold prior to investigating the evidence from your investigation.

Common A Priori Assumptions

Below, we give some examples of commonly held a priori assumptions that can easily get in the way of having productive, intellectual conversations. I will try to point out some of the flaws involved, and later I will discuss how we can do our part to address these flaws.

Political Alignments

One example that comes to mind in particular is in the abortion debate. To be absolutely clear, I am doing my best to state what I consider to be assumptions – meaning I have rarely or never heard anyone of that position actually say these things out loud. As far as I can tell, most pro-choice supporters carry the subconscious assumption that the only reason for opposition to abortion is sexism of some form (namely, discrimination with respect to reproductive rights). In other words, “My Body, My Choice“. And as far as I can tell, many pro-lifers carry the assumption that everyone consciously believes/knows that everyone agrees that a fetus is a human being with the same rights as all other human beings. In others words, “Abortion is Murder“.

I am not here taking a side on the abortion issue. My point is entirely separate from this. If you look at mainstream dialogue, as far as I can tell, the argument rarely gets down to the important points that lie at the core. If I spent longer thinking about this, I could probably come up with of other neglected but important points of discussion within the abortion debate, and I can come up with similar underlying points within other political debates. For an example of such a position, I believe that the entire gay marriage debate basically boils down to what the word marriage means and what legitimate role the government has within that institution. As far as I can tell, it has almost nothing to do with homophobia. It just doesn’t. You could hate gay people but still support gay marriage, and you could affirm loving homosexual relationships and reject gay marriage. It all depends on what you think these words mean.

My only point here is that in politics, we often don’t every get around to discussing our real differences. We get caught up in catchy and clever-sounding sound-bite comebacks. But every time I’ve thought about a “sound-bite” from either liberals or conservatives, I have found it incredibly lacking in content. We need to do better in political discourse.

Scientific Atheism/Methodological Naturalism

There is another public debate in which I see a priori assumptions playing a significant role, and this is the debate between science and religion. Both sides tend to assume, a priori, that their own perspective is superior to others in obtaining truth about reality. That is, you have many religious people that, although both science and religion can hold truths, say that truths taken from the Bible automatically override truths from science. And many atheists do the opposite – they assume that anything science says automatically overrides anything outside of science.

But, how do we know which of these assumptions is true? And is it possible that science and religion are actually entirely compatible? I believe they are compatible, but that isn’t the point I’m trying to make here, so I will leave that for another time.

People who are very religious (let’s say Christians for the sake of discussion, although a similar idea holds for other religions) may subconsciously assume a doctrine of inerrancy and hold their atheist interlocutor to that standard. Similarly, an atheist may implicitly assume methodological naturalism (a philosophical doctrine that only non-supernatural entities can be posited as explanations) and expect a religious person to also hold to that. But these are fundamentally incompatible – so of course people who hold to these two, respectively, might not agree on something. The real question is, which is a better assumption – methodological naturalism or inerrant Scriptures? That is a question that debates about evolution and the book of Genesis cannot answer – the discussion has to be philosophical

What To Do With Assumptions When Others Disagree?

Very often, our disagreements with people boil down to our assumptions. Therefore, in order to be effective in convincing a person of your beliefs, your approach should take into account the underlying assumptions of both yourself and others.

Figure Out What the Assumptions Are

The first thing we must do is to boil down any debate to its presuppositions is to ask lots of questions. In particular, the beginning of any discussion should consist in lots of “what” questions. These help to clarify the topic of the discussion. After that, we can ask “why” questions in order to boil down the discussion to its foundational pieces. The theme of what/why questions is almost always helpful in any discussion, and is always a great thing to keep in mind.

How will we know when we are at the assumption level? One way to know would be if the “why” question no longer has a helpful answer. For instance, asking a person how they know they exist wouldn’t really have a helpful answer. Alternatively, the level of ‘assumption’ can be located by starting from the obvious claims – things like “we all exist” – and moving gradually upward in complexity/controversy until a point of disagreement arises.

We can view the abortion debate as an example. Although there are multiple ways to approach this debate, and I do not intend here to defend one side or another, I think that since people are fairly familiar with this debate, it will serve as a helpful example. As a jumping-off point, here is a “bottom-up” structure of how a pro-life advocate might arrive at his or her pro-life position.

  • God exists.
  • God is the creator of humanity.
  • God values humanity.
  • God values all human beings individually.
  • All human beings have infinite moral value.
  • An unborn child is a human being. Therefore, an unborn child has infinite moral value.
  • Unjustified killing of a human being is evil. Therefore, killing an unborn child is evil.
  • Abortion kills an unborn child. Therefore, abortion is evil.

The point here is not to agree or disagree with any of these ideas. My point here is that you could disagree with this person’s pro-life position for a variety of reasons. If you don’t think God exists, then you will have a problem with a fair amount of the points involved. If you believe God exists but you are a “deist,” then you will disagree with “God values humanity,” since on deism God is distant and removed from the physical world. You might disagree on the proper way to instill moral value on a human life, or when a human life begins, and so only disagree with this person later in their train of thought. If two people are having a conversation and misunderstand where the disagreements actually lie, then it will be an unhelpful conversation. This is one of many reasons why identifying underlying assumptions is so helpful.

Now, we can discuss some options of how to carry forward in a discussion once our assumptions are identified.

Option 1: Convince them of the assumption: One way to handle a disagreement like this is to stop debating the ‘endpoint’ but to shift the conversation to the real disagreement – the underlying assumptions.

Option 2: Convince them of your point using their assumption: This method won’t always work, but sometimes it does. Sometimes, you might be able to convince a person that they have not carried out their assumptions to their logical conclusions. This is very similar to the mathematical and philosophical method of reductio ad absurdum.

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