Why should we use the rules of logic

I have written a few articles recently speaking of logic, propositions, and beliefs. Some folks agree, and others do not, so I thought I would expand on why I believe we should be using the rules of logic.

In CMT5 – I don’t believe, I tried to explain the difference between how folks used the term normatively and descriptively. I think there could be confusion around what those terms mean in the first place so let’s start there.

The difference between normative and descriptive


Normative is a process of normalisation, essentially standardising something. What it means when you’re speaking of things is the way things ought to work, the way they ought to be used.

When we speak about how we ought to answer propositions using formal logic, it is providing an epistemological answer rather than just describing a psychological state.

Another way to think of this is, something normative is what all rational persons would choose/describe given the same information.


When we say descriptive, you are describing a process in how it might be used or works in practice. It might not follow the rules of logic or could be using a unstandardised definition.

When we speak about how someone might answer a proposition descriptively, they might be giving us an answer purely on their psychological state rather than giving an epistemological answer.

Normative vs Descriptive Use

To use a silly example to accentuate the point:

The word ‘hello’ (in English) is normalised as a greeting to other people.
In a random (English speaking) society ‘hello’ could mean ‘fuck you’.

“well in <random society> hello means fuck you so it isn’t always a greeting!”

This would be comparing the way it ought to work to how it actually works in a particular society.

So Why Should We Be Logical or Speak Normatively?

As sceptics and/or atheists, we say we hold the more rational position. We tend to be the more rational and logical people therefore we should do our best to use rules of logic when we are talking about things.

Acting rationally is reasoning according to the rules of logic and probability theory, if you want to call yourself rational then you have to reason using the rules of logic!

When we don’t, we are muddying the water. The terms are being used descriptively which could create a framing error, and thus are acting irrationally.

Let’s look at the examples below.

Logical Propositions in a Dichotomy

If you have a dichotomous situation, you have 2 propositions but 3 answers.

So you will have P – the proposition, and Not P – the negated proposition which in turn forms its own proposition.

Let’s think about a light switch with a broken bulb.


P1 – the light switch is on
Not P1 – the light switch is not on which forms P2
P2 – the light switch is off
(P2 is the same as not P1)


a) P1 is true – The light switch is on
b) P2 is true – the light switch is off
c) Withholding Judgement – Neither P1 nor P2 are true or false


a) I believe answer a is true – I believe P1 is true
b) I believe answer b is true – I believe P2 is True / I disbelieve P1
c) I believe answer c is true – I don’t know if either, nor believe neither P1 or P2 to be true or false. I am in a state of unbelief/non-belief (this could be due to lack of information or something else causing uncertainty).

How Would This Be Answered Normatively?

aka how should we “ought” to answer this.

Let’s say you’re having a conversation with someone, and they assert P1 is true.

light bulb off

Them: “The light switch is on”
You: “I don’t believe you”
Them: “You believe it is off?”
You: “Yes”

Following the rules of logic, you only actually need the first 2 lines of that conversation, I am just putting line 3 and 4 in there to demonstrate the simplicity of logic.

Not believing P1 means you believe the opposite, P2.
They Assert P1 is True.
You saying you don’t believe P1 is true, means you believe P2 is true.
e.g. NOT A = B

How Does This Get Answered Descriptively?

confused bulb answered discriptively

Them: “The light switch is on”
You: “I don’t believe you”
Them: “You believe it is off?”
You: “I didn’t say that”
Them: “Um, so what do you believe?”
You: “I don’t have enough information to believe either way. I don’t know”

What they are doing, instead of following the rules of logic, is answering the question descriptively. They are describing a psychological state, but are not giving you the whole answer.

Instead of NOT A = B, they don’t believe either A or B to be true. Their answer is actually C.

They have muddied the water by just answering with a psychological state of disbelief instead of answering the proposition in a logical manner. In truth, they are not even using disbelief correctly here, they actually mean unbelief.

They could have said, “I don’t know” or “I am unsure” which would have answered the question in full, but instead used an option that sounds like a complete answer, when in fact it is being used in an ambiguous way.

You are having to ask further questions to clarify the position instead of it being simple to understand.

Option C is essentially the classic Agnostic position, I don’t know enough to believe either option is true or false.

Isn’t a Positive/Negative Attitude a Psychological State Though?

Yes, but what I am referring to here is; with normative logic, the positive/negative attitude is answering the question logically, directly and concisely.

When you answer it descriptively, you are skipping the logic part. You are simply describing the attitude ambiguously/erroneously. If you are a logical person people will assume you are using the rules of logic, but if you are not you might get annoyed at them assuming what you believe.

skipping logic leads to unclear answers

By skipping the logic, and using disbelief descriptively, the answer is unclear. Rather than disbelief in a normative sense, they actually mean unbelief. You are providing commentary on a psychological state rather than giving an epistemological answer.

Summary So Far

When you answer the proposition normatively, you give a direct answer to the proposition. This gives a clear epistemological answer to the proposition and yes, results in a psychological state. When you answer descriptively, you are skipping over the logic part, and just describing your psychological state and not providing an epistemological answer. You might also be conflating disbelief with unbelief.

So How Do We Apply This Logic to Theism, Atheism, and Agnosticism?


P1 – God Exists
P2 – God Does not Exist


a) P1 is true – Theism
b) P2 is true – Atheism
c) Withholding Judgement – Neither P1 nor P2 are true or false – Agnosticism


a) I believe answer a/P1 is true – Theist
b) I believe answer b/P2 is true – Atheist
c) I believe answer c/I don’t know if (or believe) either P1 or P2 are true or false – Agnostic

You might answer c for a number of reasons, but the main one would usually not enough knowledge to make a judgement either way.

How Do These Propositions Get Answered Normatively?

Them: “God Exists”
You: “I don’t believe you”
Them: “So you believe God does not exist?”
You: “Yes”

Again lines 3 and 4 are not actually needed in the conversation, they are just highlighting the point.

And Now For Descriptive Again?


Them: “God Exists”
You: “I don’t believe you”
Them: “You believe God does not exist??”
You: “I didn’t say that”
Them: “Um, so what do you believe?”
You: “I don’t have enough information to believe either way. I don’t know”

So again, the water was muddied by them not answering in a normative and logical manner. We have to ask additional questions to find out what they DO believe, and the answer is they don’t know. The logic has been jumped over and they are describing a cognitive state in an ambiguous/erroneous way.

So where they are negating P1, they should be believing P2 (b) – but instead, they are not believing either to be true or false and therefore their answer should be c.

So Most Atheists Are Actually Agnostics?

Language changes and evolves through use, so it is best to clear up your definition first rather than say “You are using atheist wrong!” or “Agnosticism should not be used as a modifier for atheism” especially as atheism is actually polysemous like many words.

However, based on classical definitions, that are still used and most widely accepted in philosophy – Yes! I don’t fully understand why they don’t identify as such. There is nothing wrong with either position, and I wonder if it is just a misunderstanding of logic or language that leads them to use the atheist tag?

These words describe a position on a topic, but essentially we are conflating agnosticism with atheism instead. That’s like being a centrist politically and voting far left/right.

I don’t really want to assume anything about folks, but when I ask people these questions they don’t really have an answer. It seems like they have been programmed to say certain things reactively and haven’t fully analysed what they believe or what they are saying.

Perhaps it is more to do with the prevalence of misused logic within the community. You could argue this is a form of dogmatism.

This too could be why they (and I historically) use terms such as agnostic atheist.

Does it Matter How We Are Using The Language?

Whilst language evolves, and I don’t really care if someone who is actually agnostic is identifying as an atheist or agnostic atheist, I do encourage folks to be as logical and accurate as they can be. I have corrected many errors in my beliefs as I have gained knowledge, especially around logic and epistemology, but I do find some folks refuse to learn and grow. Often choosing to appeal to authority from some “king atheist” as if they are some sort of pope of atheism rather than think about these things themselves.

Equally, if we are speaking of philosophical concepts, be it atheism, morality, virtue ethics etc we should be using the philosophical language. Saying “I haven’t studied philosophy” is not an excuse. If you don’t know, fine, but you should either endeavour to learn the correct terminology, or at least listen when someone corrects you. Otherwise, if you are peddling erroneous information without having any real grounding in the subject you are demonstrating aspects of the Dunning-Kruger effect.

Consider if we are speaking of evolution and we want people to use scientific terminology. If someone comes along and starts using terms like “kinds” and phrases like; “it’s a changing of kind”, this is not an accepted scientific term so by that notion we discredit what they’re saying. We assume they clearly do not understand evolution. They don’t understand the science or the evidence because if they did they would be using the correct terminology.

Similarly, if we are speaking to a theist about a theological problem we should be using the theological language. We should not refer to God as the magical sky daddy unless we are just trying to be condescending patronizing pricks.

So back to the philosophical conversation; atheism and theism are philosophical concepts and we should use the philosophical definitions and rules of logic otherwise we are being illogical.

This, in turn, is why we can argue that even though atheism is polysemous, some of the definitions are illogical, and terms like agnostic atheist are nonsensical.

In Summary

I will say this again; acting rationally is reasoning according to the rules of logic and probability theory, if you want to call yourself rational then you have to reason using the rules of logic.

If you follow the rules of logic, it is hard to see atheism, theism and agnosticism as any but the 3 mentioned in this article. However if logic is not important to you and you agree with the majority of the atheists on the internet, and admittedly a few philosophers (although very few), then by your definition all agnostics are also atheists.

I agree with the definitions in this article because they are the most logical, but I understand the descriptive use when the rules of logic are not followed. As demonstrated in this article, following the rules of logic makes the conversations simple and the classifications clear.

The colloquial use of these terms (e.g. atheist being anyone who is not a theist, agnosticism only relating to knowledge), the modifiers (e.g. agnostic/gnostic theist/atheist) and the herd mentality adds a number of unnecessary layers, blurs lines, and does not follow the rules of logic to answer the propositions in a simple and concise manner.

If you are discussing topics from a particular genre, be it science, theology, philosophy, or anything else, you should endeavour to use the proper terminology.

If you haven’t studied the topic, be it logic, philosophy, science etc, it might be worth double-checking multiple credible sources. At least then if you maintain your definition/position you will be well versed to justify why.

Related Articles & Podcasts

I often include references these days, as well as links to articles, however, all of the articles below contain the references used in this post, and go into more details about each item discussed within this post.