How Belief Works

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

The surprisingly basic logical flaw 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 a surprisingly basic logical flaw 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, 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 – 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.

Note that the following claim is just another wording of claim 2:

It's true that it rained yesterday.

It can seem to simply refer to 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 claim is actually stating that the claim It rained yesterday is a true claim – claim 2 – even though it doesn't refer to this claim as a claim as claim 2 does.

All of this applies to any claim, X. That is, the claims X and The claim X is true are different claims. And the latter can be shortened to X is true, even though this wording, unlike the original, doesn't refer to X as a claim.

Even dictionaries often conflate the claims X and X is true. For example, Oxford University Press's online dictionary defines the noun 'claim' as 'An assertion that something is true', and Cambridge University Press's online dictionary defines it as 'a statement that something is true or is a fact, although other people might not believe it'.

The logic of this section also applies to any two claims of the form Not X and X is false. For example, compare these two claims:

    1. It didn't rain yesterday.

    2. The claim It rained yesterday is false.

Whereas claim 1 simply concerns yesterday’s weather, claim 2 concerns a claim about yesterday’s weather.

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. 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.

All of this applies to our belief of any claim, X. That is, belief X and belief X is true are different beliefs.

Believing X doesn't itself involve believing that X is true – it simply involves, as I stated in chapter 2, the content of X being our understanding of part of reality. To be clear, the content of X being our understanding of part of reality is different from us believing that X matches reality, which is just another wording of believing that X is true – as is believing that X is the case, or 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 definition 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. And of those definitions that I've read which don’t state this, none actually dispute this understanding of belief. This is a ninth way in which belief is misdefined, in addition to the eight that I listed in chapter 2.

The above logic also applies to our belief of any two claims of the form Not X and X is false. For example, compare our belief of these two claims:

  1. It didn't rain yesterday.

  2. The claim It rained yesterday is false.

Again, given that these claims are different claims, our belief of them are different beliefs.

Note that believing X is false constitutes disbelieving X. Therefore, whereas believing X doesn't itself involve believing that X is true, disbelieving X involves believing that X is false. Also, to be clear, believing Not X doesn't constitute disbelieving X. Disbelieving X concerns the truth of X, whereas believing Not X doesn't. For example, believing the claim It didn't rain yesterday doesn't concern the truth of the claim It rained yesterday, but merely concerns yesterday's weather.

The conclusion that believing X doesn’t itself involve believing that X is true doesn’t disprove the idea that we believe X because we’ve assessed that X is true. However, there’s a surprisingly basic logical flaw in this theory of belief formation.

The true relationship between belief and an assessment of truth

Again, the concept of truth concerns the relationship between a claim and reality. A true claim is a claim that 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 a conclusion is obviously preceded by the formation of a belief on which the conclusion is based. Therefore, contrary to the current understanding, our belief that it rained yesterday can’t, as a matter of surprisingly basic logic, be due to us assessing that the claim It rained yesterday is a true claim.

And this applies to the formation of any belief, by any form of intelligence: belief X can’t, as a matter of surprisingly basic logic, be due to the believer assessing that X is true, even though this theory of belief formation can seem true by definition. Instead, the believer's assessment that X is true is due to their belief of X.

Note that, although our belief X can't be due to our assessment that X is true, the process of assessing the truth of X can lead to us believing X. That is, our belief X may form during that process, and possibly only the moment before we conclude that X is true.

Also, 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.

There's actually a second surprisingly basic logical flaw in the idea that we believe something because we’ve assessed that it’s true. Given that the claims X and X is true are actually different claims, 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, indefinitely. Belief formation would therefore be impossible, and yet we easily, and constantly, form beliefs.

Possible objections

Objection 1

It might 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 true and that contrary claims are false, and we'd therefore never change our belief, and yet we do sometimes change a belief.

However, the logic of this objection assumes that changing our belief of X is dependent on us assessing that X is false and that a contrary claim is true. But just as the formation of our belief of X wasn't due to our assessment that X is true, because the reverse is the case, so the subsequent formation of a contrary belief, and thus the ending of our belief of X, won't be due to us assessing that the contrary claim is true and that X is false, because the reverse is the case. As I explained in the previous section, the process of assessing the truth of X can lead us to belief X, but our assessment that X is true comes after the formation of our belief of X. Likewise, if we believe X and then assess the truth of a contrary claim and X, this process can lead us to instead believing the contrary claim, but our assessment that the contrary claim is true and that X is false comes after this change of belief. So our belief of X actually doesn't even mean that we'll always assess that X is true and that contrary claims are false, because we can change this belief between its formation and the conclusion of our assessment.

Objection 2

It might also be objected that there's one type of occasion when we definitely believe something because we’ve assessed that it’s true. If we hear or read a claim, X, that we don’t already believe, and it’s made by someone who we think won’t be wrong on the subject of X, then we'll conclude that X must be a true claim, and therefore then conclude X.

However, although our belief of X can indeed form in this way, our conclusion that X is true doesn't, in such cases, actually constitute an assessment that X is true. By definition, X is true if, and only if, it matches reality. Therefore, by definition, to assess that X is true is to assess that it matches reality. And the only way to genuinely assess whether X matches reality is to compare it with reality – that is, compare it with what we believe is reality at the moment of the comparison. But in the above scenario our conclusion that X is true is the product not of a comparison of X and reality, but of a consideration of the source of X. That is, the assessment that we perform is of not X’s truth, but its source, and we then conclude from that assessment that X must be true, and therefore then conclude X. Therefore our belief of X is due to us concluding, but not assessing, that X is true.

The origins of this misunderstanding

As I've mentioned, the logical flaw in the current idea that we believe something because we’ve assessed that it’s true is surprisingly basic. That is, given that, by definition, the claim It rained yesterday is a true claim if, and only if, it rained yesterday, our assessment that this claim is a true claim is obviously dependent on our prior belief that it rained yesterday. It therefore may seem implausible that this flaw in this theory of belief formation hasn’t been identified before. And perhaps it has been. But if it has then it has evidently failed to become widely accepted, even within academia. No book or paper on psychology or philosophy that I’ve read refers to it.

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 five factors:

    1. We can wrongly think that the claims X and X is true are just different wordings of the same claim, and therefore that the beliefs X and X is true are the same belief.

    2. Given the speediness of the brain – which works on the timescale of milliseconds – our conclusion that X is true may form so soon after the formation of our belief of X that these two events can seem to be the same event.

    3. If our belief of X forms during the process of assessing the truth of X, then that assessment was a factor in the formation of our belief of X, and this can lead us to the false assumption that our belief of X is due to our assessment that X is true.

    4. When we compare X with reality, in order to assess X’s truth, we can easily forget that we ultimately can only ever compare X to 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, based on our belief of X, we can wrongly think that we're comparing X with reality itself, and then 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.

    5. When we conclude that 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 that claim X is merely a possibility, then we don't at that point believe X. But in this scenario our conclusion is the claim X is a possibility, 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 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.

As I explained, our belief of X can be due to us concluding X based on our prior conclusion, but not assessment, that X is true, when this claim is made by someone who we think won’t be wrong on the subject of X.

Even the formation of beliefs about our surroundings via sensory perception involves at least some reasoning about the content of our perceptions. As with any belief, such a belief involves a specific claim – a claim about our surroundings, such as It’s raining. And also as with any belief, the formation of such a belief involves thinking the claim concerned. For example, the formation of the belief It’s raining involves thinking It’s raining. But the output of the perceptual process is simply our sensory experiences of our surroundings, via our sense organs, and such experiences don't themselves 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 itself involve thinking claims about the scene. But such thoughts can 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 fast, that the resulting belief can seem to be a direct product of the process of visual perception. And likewise for our other senses.

To be clear, the term perception can be used in the sense of a belief, as in 'It's my perception that she's dishonest', but the above paragraph is referring to perception in the sense of sensory perception.

The theory that we believe X because X was the product of our reasoning can seem true by definition and therefore unimpeachable, but so did the theory that we believe X because we’ve assessed that X is true. Indeed, even this second theory is wrong, as I show in chapter 5.

But in the next chapter I show that the analysis in this chapter also has a significant implication for the nature of belief.


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