How Belief Works

Chapter 3: Why Do We Believe What We Believe?​

The surprisingly basic logical flaws in the idea that we believe something because we’ve assessed that it’s true​

The answer to the question of why we believe what we believe can seem not just obvious, but true by definition: we believe something because we’ve assessed that it’s true. Indeed, this idea is widespread within psychology and philosophy. However, I discovered surprisingly basic logical flaws in this supposed truism.

Claim X versus the claim X is true

First compare these two claims:

    1. It rained yesterday.

    2. The claim It rained yesterday is true.

They can seem to be claiming the same thing – that it rained yesterday – and therefore to be just different wordings of the same claim. But they’re actually claiming something different, albeit closely related. Whereas claim 1 simply concerns yesterday’s weather, claim 2 concerns a claim about yesterday’s weather. That is, claim 2 concerns claim 1:

Whereas claim 1 is simply claiming that it rained yesterday, claim 2 is claiming that the claim It rained yesterday is a true claim. The two claims merely logically imply each other. If it rained yesterday – claim 1 – then, logically, the claim It rained yesterday is a true claim – claim 2. Conversely, if the claim It rained yesterday is a true claim then, logically, it rained yesterday. The two claims can seem to be just different wordings of the same claim because they each follow so obviously from the other that we can fail to notice the basic logical step separating them.

The following claim is just another wording of claim 2:

It's true that it rained yesterday.

It can seem to simply concern yesterday's weather, rather than a claim about yesterday's weather, and therefore seem to be just another wording of claim 1. However, it refers to the truth of something, and the concept of truth concerns a claim – specifically, the relationship between a claim and reality. Therefore the above claim is actually stating that the claim It rained yesterday is a true claim – claim 2 – even though it doesn't refer to the claim It rained yesterday as a claim as claim 2 does.

The difference between claims 1 and 2 applies to any two claims of the form X and X is true.

Even dictionaries often conflate the claims X and X is true. For example, Oxford University Press's online English dictionary defines the noun 'claim' as 'An assertion that something is true', and Cambridge University Press's online English dictionary defines it as 'a statement that something is true or is a fact ...'.

Belief X versus the belief X is true

Now compare our belief of these two claims:

    1. It rained yesterday.

    2. The claim It rained yesterday is true.

Given that these claims are different claims, our belief of them are different beliefs. That is, believing that it rained yesterday merely implies that we would conclude that the claim It rained yesterday is a true claim. Conversely, believing that the claim It rained yesterday is a true claim merely implies that we believe that it rained yesterday. But these beliefs can seem to be the same belief that it rained yesterday – because they each follow so obviously from the other that we can fail to notice the basic logical step separating them.

The difference between our belief of claims 1 and 2 applies to our belief of any two claims of the form X and X is true. Believing X therefore doesn't in itself involve believing that X is true. Instead, believing X simply involves, as I stated in chapter 2, the content of X being our understanding of part of reality. The content of X being our understanding of part of reality is different from us believing that the content of X matches reality, because that's believing that X is true – as is believing that X is the case, or believing that X is so.

This distinction between believing X and believing that X is true is contrary to the current understanding of belief. For example, the Oxford English Dictionary defines believe as ‘to consider to be true’, and the American Psychological Association Dictionary of Psychology and Stanford Encyclopedia of Philosophy define belief likewise. And most of the other formal definitions of belief that I’ve read, including in academic papers and books on psychology and philosophy, state that it involves considering something to be true. This is therefore a ninth way in which belief is misdefined, in addition to the eight that I listed in chapter 2. Also, none of the definitions of belief that I've read which don’t state this actually dispute this current understanding of belief.

The true relationship between belief and an assessment of truth

It might be thought that the conclusion that believing X doesn’t in itself involve believing that X is true doesn’t disprove the idea that we believe X because we’ve assessed that X is true, because our belief of X could be dependent on us first believing that X is true. However, that's actually logically impossible. If believing X was dependent on us believing that X is true, then believing that X is true would in turn be dependent on us believing that the claim X is true is true, and so on, which implies an infinite chain of belief formation. Belief formation would therefore be impossible, and yet we easily and constantly form beliefs.

There's actually a second logical flaw in the idea that we believe something because we’ve assessed that it’s true, and it reveals the true relationship between belief and an assessment of truth.

Again, the concept of truth concerns the relationship between a claim and reality. A claim is a true claim if, and only if, its content matches reality. Therefore the claim It rained yesterday is a true claim if, and only if, it rained yesterday. Therefore our assessment that the claim It rained yesterday is a true claim must be based on our belief that it rained yesterday. And the formation of the conclusion of an assessment is obviously preceded by the formation of a belief on which the conclusion is based. Therefore our assessment that the claim It rained yesterday is a true claim must actually be preceded by our belief that it rained yesterday. Therefore our belief that it rained yesterday can’t ever be due to us assessing that the claim It rained yesterday is a true claim. Instead, that assessment is always due to that belief. And this logic applies to the formation of any belief, by any form of intelligence: belief of claim X can’t ever be due to the believer assessing that X is a true claim, because that assessment is always due to that belief.

So, as a matter of surprisingly basic logic, we don't believe something because we’ve assessed that it’s true, even though this theory of belief formation can seem true by definition. Although, the process of assessing the truth of claim X may lead to the formation of our belief of X, because this belief may only form during that process, and possibly only the moment before we conclude that X is true. Note also that even our assessment that X is true isn’t an instance of believing something because we’ve assessed that it’s true. This belief involves the claim X is true, but is formed via an assessment that X, not X is true, is true.

Potential objections

Objection 1

It might be objected that our assessment that claim X is a true claim can also be based on our trust of its source, and this assessment then leads us to conclude X. This possibility doesn't involve the above-mentioned infinite chain of belief formation because it doesn't imply that our belief of any claim is dependent on us believing that the claim is a true claim. Indeed, given that our belief that X is true is based on our trust of its source, it wouldn't be based on the belief that the claim X is true is true.

However, if our conclusion that a claim is a true claim is formed in this way then it actually wouldn't constitute an assessment that the claim is a true claim. Again, a claim is a true claim if, and only if, its content matches reality. Therefore, by definition, to assess that a claim is a true claim is to assess that its content matches reality. And the only way to genuinely assess whether the content of a claim matches reality is to compare that content with reality – that is, to compare it with what we believe is reality. Therefore if our conclusion that a claim is a true claim is based on simply a consideration of its source, and therefore not on a comparison of its content with reality, then it's based on an assessment of not its truth but that source. Therefore, although our conclusion that X is a true claim can be based on our trust of its source, and this conclusion then leads us to conclude X, our belief of X wouldn't be due to us assessing that X is a true claim.

Objection 2

It might also be objected that if our assessment that claim X is a true claim is based on our belief of X, rather than the reverse, then our belief of X would lead us to always assess that X is a true claim and that contrary claims are therefore false, and we'd therefore never change our belief, and yet we do change our beliefs. However, this objection wrongly assumes that if we believe X then changing this belief is dependent on us assessing that a contrary claim is a true claim and that X is therefore a false claim. Just as our belief of X can't due to our assessment that X is a true claim, because the reverse is true, so the subsequent formation of a contrary belief, and thus the end of our belief of X, can't be due to us assessing that the contrary claim is a true claim and that X is therefore a false claim, because the reverse will be true. As I mentioned, the process of assessing the truth of X can lead to the formation of our belief of X, because this belief may only form during that process. Likewise, if we believe X and then assess the truth of both X and a contrary claim, this process can lead to us instead believing the contrary claim, and we can then our assess that the contrary claim is a true claim and that X is therefore a false claim. So our belief of X actually doesn't mean that we'll always assess that X is a true claim and that contrary claims are therefore false, because we can change this belief during such assessments.

The origins of this false theory of belief formation

Again, the two logical flaws in the idea that we believe something because we’ve assessed that it’s true are surprisingly basic. It therefore might seem implausible that they haven’t been identified before. And perhaps they have. But if so then they've evidently failed to become widely recognised, even within academia. I'm not aware of any book or paper on psychology or philosophy that refers to even one of these two logical flaws in this theory of belief formation.

The origin and persistence of the idea that we believe something because we’ve assessed that it’s true will be due to the combination of the following four factors:

    1. Given that the beliefs X and X is true each follow so obviously from the other we can fail to notice the basic logical step separating them, and so wrongly think that they're the same belief, especially given the speediness of the brain, which works on the timescale of milliseconds.

    2. If our belief of claim X formed during the process of assessing the truth of X, then that process was a critical part of the mental chain of events that led to our belief of X. And this fact can lead us to wrongly think that our belief of X is due to our assessment that X is true, especially if our belief of X formed only the moment before we concluded that X is true.

    3. When we compare the content of claim X with reality in order to assess the truth of X we can easily forget that we ultimately can only ever compare the content of X with what we believe is reality at the moment of the comparison, even when that belief is based on the current content of our senses. Therefore when we assess that X is true we can wrongly think that we're comparing X with reality itself, and therefore only believing X upon assessing it to be true. We’re especially likely to make this mistake given that, as I show in the next chapter, belief is certainty, contrary to the current understanding that we can hold sub-certain beliefs.

    4. When we conclude that claim X is true based on our assessment of the source of X, and therefore then conclude X, we can wrongly think that we believe X because we assessed that X is true.

So why do we believe what we believe?

There’s actually a third surprisingly basic logical flaw in the idea that we believe something because we’ve assessed that it’s true. We obviously can only begin to assess the truth of a claim after it has entered our mind. But a conclusion is, by definition, a claim that we believe upon it entering our mind via our reasoning. So we believe such a claim before we've had a chance to assess its truth. Of course, if our conclusion is merely that the content of claim X is a possibility, then we don't at that point believe X. But in this scenario our conclusion is the claim It's possible that X, which we do believe upon it entering our mind.

This point also provides an alternative answer to the question of why we believe what we believe: we believe claim X not because we've assessed that X is true, but because we've concluded X. That is, we believe X because X was the product of our reasoning. Again, our belief of X can be due to us concluding X based on our prior conclusion, but not assessment, that X is true because we trust the source of X.

Even the formation of beliefs about the nature of, and events in, our surroundings via perception involves at least some reasoning about the content of our perceptions. The term perception can itself be used in the sense of a belief, as in 'It's my perception that she's dishonest', but I'm referring here to sensory perception. And given that any belief involves a claim, a belief formed via perception involves a claim about our surroundings, such as It’s raining. And the formation of any belief involves thinking the claim concerned. So the formation of the belief It’s raining involves thinking 'It’s raining'. But the output of the perceptual process is simply our sensory experience of our surroundings, which doesn't in itself involve thinking claims about our surroundings. That is, perception and thinking are distinct forms of cognition. For example, consider vision and thinking. Our vision of the scene in front of our eyes is simply our visual experience of that scene, and therefore doesn't in itself involve thinking claims about the scene. Such thoughts can instead be the product of our reasoning about the content of our vision, aided by our memory and imagination. However, such reasoning is often so basic and therefore brief, especially given the speediness of the brain, that the resulting belief can seem to be a direct product of the process of visual perception. And likewise for our other senses.

The theory that we believe claim X because we've concluded X – that is, because X was the product of our reasoning – can seem true by definition and therefore unimpeachable, but so can the theory that we believe X because we’ve assessed that X is true. And I show in chapter 5 that even this second theory of belief formation is wrong. But it's necessary to first consider the nature of belief.

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