What can I know with complete certainty?

[Compassionist]

I am completely certain of the following:

1. I am conscious.
2. I am typing in English.
3. I am not all-knowing.
4. I am not all-powerful.
5. I change.
6. I can't do lots of things I really want to do e.g. go back in time and prevent all suffering, inequality, injustice, and deaths and make all living things forever happy.
7. I do some things even though I don't want to do them. Here are some things I have done, currently do or will do even though I don't want to do them:

1. Breathe
2. Eat
3. Drink
4. Sleep
5. Dream
7. Pee
8. Poo
9. Fart
10. Burp
11. Sneeze
12. Cough
13. Age
14. Get ill
15. Get injured
16. Sweat
17. Cry
18. Suffer
19. Snore
20. Think
21. Feel
22. Choose
23. Be conceived
24. Be born
25. Remember some events that I don't want to remember
26. Forget information that I want to remember
27. Die

I am almost certain of the following:

1. I and all the other organisms currently alive will die. Every second brings all organisms closer to death.
2. My body, other organisms, the Earth and the Universe really exist and they are not part of a simulation or hallucination or dream or illusion.
3. Other organisms e.g. humans, cows, dogs, cats, chickens, pigs, lions, elephants, butterflies, whales, dolphins, etc. are sentient beings who feel pain.
4. Being a non-consumer is more ethical than being an autotroph, being an autotroph is more ethical than being a vegan/herbivore, being a vegan is more ethical than being a vegetarian, and being a vegetarian is more ethical than being an omnivore or carnivore.
5. Gods do not exist.
6. Souls do not exist.
7. Reincarnation does not happen.
8. Resurrection does not happen.
10. Organisms evolved and were not created by God or Gods.
11. 99.9% of all the species to evolve so far on Earth became extinct in 5 mass extinctions long before humans evolved.
12. Humans and other organisms do not have free will. Our wills are determined and constrained by our genes, environments, nutrients, and experiences. The reason I have put this one in the almost certain category is that it is possible that bodies, genes, cells, stars, planets, moons, galaxies, universes may not actually exist. These things could be part of a simulation or dream or hallucination or illusion. It is impossible to know with complete certainty. I could be a solipsistic soul experiencing the illusion of being in a human body on a planet in a universe or I could be a body without any soul - I don't know these things for sure, hence I am an agnostic. There are many hypotheses that can't be tested e.g. simulation hypothesis, illusion hypothesis, dream hypothesis, hallucination hypothesis, solipsism hypothesis, philosophical zombie hypothesis, panpsychism hypothesis, pantheism hypothesis, etc. Just because a hypothesis can't be tested it does not mean it is true or false. It just means that it is currently untestable.

[boatsnguitars]

It's a good list. If only others agreed, we could have a better existence. No war, strife, disease - because we'd get on with the actual business of reality instead of spending all our time and resources on fantasies filled with hatred.

[Compassionist]

It's a good list. If only others agreed, we could have a better existence. No war, strife, disease - because we'd get on with the actual business of reality instead of spending all our time and resources on fantasies filled with hatred.

Thank you. I agree with you.

[elphidium55]

Can I be completely certain of the claim "There is no beer in the frig!"? If I was desperate enough for a beer would it be wrong for me to take a look in the frig? What should I think if I see a shopping list with a checkmark next to the words "buy beer"? If I see a receipt from the grocery store on the kitchen table which includes a charge for a six pack of beer, should I revise my belief? What if the refrigerator door mysteriously falls open and I see it's full of beer? Should I deny what I see right in front of me? Or does my certainty make my no-beer belief unreviseable?

I am sympathetic to what is know as "phenomenological conservatism" (henceforth, PC). PC defends the view that our sensory perceptions about middle sized objects in everyday contexts are broadly reliable. If it looks like a duck and waddles like a duck and quacks like a duck, we have prima facie justification for believing it is a duck (at least in the absence of reasons to the contrary). Such beliefs are defeasible - my credences can be very high or very low without having to be at 0% or 100%.

[bob the baptist]

I am completely certain of the following:

1. I am conscious.
2. I am typing in English.
3. I am not all-knowing.
4. I am not all-powerful.
5. I change.
6. I can't do lots of things I really want to do e.g. go back in time and prevent all suffering, inequality, injustice, and deaths and make all living things forever happy.
7. I do some things even though I don't want to do them. Here are some things I have done, currently do or will do even though I don't want to do them:

1. Breathe
2. Eat
3. Drink
4. Sleep
5. Dream
7. Pee
8. Poo
9. Fart
10. Burp
11. Sneeze
12. Cough
13. Age
14. Get ill
15. Get injured
16. Sweat
17. Cry
18. Suffer
19. Snore
20. Think
21. Feel
22. Choose
23. Be conceived
24. Be born
25. Remember some events that I don't want to remember
26. Forget information that I want to remember
27. Die

I am almost certain of the following:

1. I and all the other organisms currently alive will die. Every second brings all organisms closer to death.
2. My body, other organisms, the Earth and the Universe really exist and they are not part of a simulation or hallucination or dream or illusion.
3. Other organisms e.g. humans, cows, dogs, cats, chickens, pigs, lions, elephants, butterflies, whales, dolphins, etc. are sentient beings who feel pain.
4. Being a non-consumer is more ethical than being an autotroph, being an autotroph is more ethical than being a vegan/herbivore, being a vegan is more ethical than being a vegetarian, and being a vegetarian is more ethical than being an omnivore or carnivore.
5. Gods do not exist.
6. Souls do not exist.
7. Reincarnation does not happen.
8. Resurrection does not happen.
10. Organisms evolved and were not created by God or Gods.
11. 99.9% of all the species to evolve so far on Earth became extinct in 5 mass extinctions long before humans evolved.
12. Humans and other organisms do not have free will. Our wills are determined and constrained by our genes, environments, nutrients, and experiences. The reason I have put this one in the almost certain category is that it is possible that bodies, genes, cells, stars, planets, moons, galaxies, universes may not actually exist. These things could be part of a simulation or dream or hallucination or illusion. It is impossible to know with complete certainty. I could be a solipsistic soul experiencing the illusion of being in a human body on a planet in a universe or I could be a body without any soul - I don't know these things for sure, hence I am an agnostic. There are many hypotheses that can't be tested e.g. simulation hypothesis, illusion hypothesis, dream hypothesis, hallucination hypothesis, solipsism hypothesis, philosophical zombie hypothesis, panpsychism hypothesis, pantheism hypothesis, etc. Just because a hypothesis can't be tested it does not mean it is true or false. It just means that it is currently untestable.

You asked for COMPLETE certainty. Humans can not know anything with complete certainty. i.e. You can not know you are going to die, its just a good bet. If and when you do, you won't know it. But then, as a Christian, I would argue that you will most certainly know it. If I believe it, it is certainty.

[nameless]

[Replying to Compassionist in post #1]
"What can I know with complete certainty?"
~~~ That your 'beliefs' are 'right' and other conflicting/threatening 'beliefs' are wrong.
It has nothing to do with healthy rational thought.
People who know things with 'complete certainty' are known as fanatics, dangerous to self and others.
No one ever deliberately harmed another unless hosting 'beliefs' to defend or propagate.

Everything on your list can be logically and scientifically argued against!
'Beliefs' dismiss the strictures of logic and science and can eat anything that is not threatening.
First Law of Soul Dynamics; "For every Perspective, there is an equal and opposite Perspective!"

[Compassionist]

[Replying to bob the baptist in post #5]

Bob, thank you for your reply. You’re right that humans cannot know everything with complete certainty, and in that sense even my list of “certainties” might still be open to doubt in principle.

However, I draw a distinction between epistemic certainty and conviction.

Epistemic certainty means that it is impossible to be mistaken - as with “I am conscious right now.”
Conviction or faith-based certainty means “I believe this so strongly that I treat it as certain,” even if evidence or logic could, in principle, prove it false.

When you write, “If I believe it, it is certainty,” that describes conviction, not epistemic certainty. Belief can feel absolutely true, but the feeling of certainty and the fact of certainty are different things.

For example, a Muslim, Hindu, or Christian might each feel completely certain of mutually incompatible doctrines. Their feelings of certainty can’t all correspond to the truth at once. That’s why philosophers separate psychological certainty (how confident we feel) from logical certainty (what cannot be doubted without contradiction).

I agree that human knowledge is limited - including mine. But while belief can console or inspire, it’s still distinct from demonstrable knowledge. I try to reserve complete certainty for propositions that can’t possibly be false, and treat everything else as almost certain but open to revision.

[Compassionist]

[Replying to nameless in post #6]

Nameless, thank you for your thoughtful and challenging comment.

I agree with you that belief without question can become dangerous, especially when tied to ideology or identity. Fanaticism often begins where doubt ends.

However, when I speak of “complete certainty,” I don’t mean moral or ideological certainty. I mean phenomenological certainty - the kind of direct awareness that even radical doubt can’t undermine.

For instance, I can doubt the external world, my body, language, even logic itself - but I cannot doubt that something is being experienced right now. The experience of consciousness is self-evident, even if everything else about it could be mistaken or illusory.

In that sense, “I am conscious” isn’t a belief about the world; it’s a recognition of what’s immediately present. That’s not fanaticism - it’s the minimal foundation that allows all reasoning, including skepticism, to occur.

I agree that every perspective has its opposite, but the fact that opposites exist is itself something we can know with certainty: difference and awareness exist. Beyond that, I share your humility - everything else I hold only tentatively, proportioned to the evidence.

[William]

I am completely certain of the following:

1. I am conscious.
2. I am typing in English.
3. I am not all-knowing.
4. I am not all-powerful.
5. I change.
6. I can't do lots of things I really want to do e.g. go back in time and prevent all suffering, inequality, injustice, and deaths and make all living things forever happy.
7. I do some things even though I don't want to do them. Here are some things I have done, currently do or will do even though I don't want to do them:

1. Breathe
2. Eat
3. Drink
4. Sleep
5. Dream
7. Pee
8. Poo
9. Fart
10. Burp
11. Sneeze
12. Cough
13. Age
14. Get ill
15. Get injured
16. Sweat
17. Cry
18. Suffer
19. Snore
20. Think
21. Feel
22. Choose
23. Be conceived
24. Be born
25. Remember some events that I don't want to remember
26. Forget information that I want to remember
27. Die

I am almost certain of the following:

1. I and all the other organisms currently alive will die. Every second brings all organisms closer to death.
2. My body, other organisms, the Earth and the Universe really exist and they are not part of a simulation or hallucination or dream or illusion.
3. Other organisms e.g. humans, cows, dogs, cats, chickens, pigs, lions, elephants, butterflies, whales, dolphins, etc. are sentient beings who feel pain.
4. Being a non-consumer is more ethical than being an autotroph, being an autotroph is more ethical than being a vegan/herbivore, being a vegan is more ethical than being a vegetarian, and being a vegetarian is more ethical than being an omnivore or carnivore.
5. Gods do not exist.
6. Souls do not exist.
7. Reincarnation does not happen.
8. Resurrection does not happen.
10. Organisms evolved and were not created by God or Gods.
11. 99.9% of all the species to evolve so far on Earth became extinct in 5 mass extinctions long before humans evolved.
12. Humans and other organisms do not have free will. Our wills are determined and constrained by our genes, environments, nutrients, and experiences. The reason I have put this one in the almost certain category is that it is possible that bodies, genes, cells, stars, planets, moons, galaxies, universes may not actually exist. These things could be part of a simulation or dream or hallucination or illusion. It is impossible to know with complete certainty. I could be a solipsistic soul experiencing the illusion of being in a human body on a planet in a universe or I could be a body without any soul - I don't know these things for sure, hence I am an agnostic. There are many hypotheses that can't be tested e.g. simulation hypothesis, illusion hypothesis, dream hypothesis, hallucination hypothesis, solipsism hypothesis, philosophical zombie hypothesis, panpsychism hypothesis, pantheism hypothesis, etc. Just because a hypothesis can't be tested it does not mean it is true or false. It just means that it is currently untestable.

AI: Based on the data provided, here is a summary of what the author, "Compassionist," claims to know with certainty and near-certainty.

Summary of Certainties
The author is completely certain about their own immediate experience and limitations. This includes:

Their own consciousness: "I am conscious."

A specific current action: "I am typing in English."

Their personal limitations: They are not all-knowing, not all-powerful, and are subject to change.

Involuntary actions: They list 27 things their body does regardless of their will, ranging from basic biological functions (breathe, eat, sleep) to life events (be born, age, die).

Summary of Near-Certainties
The author is almost certain about the nature of reality, ethics, and metaphysics, acknowledging that these beliefs, while strongly held, cannot be proven with absolute certainty. These include:

The reality of death and existence: Everyone will die, and the physical world (bodies, Earth, universe) is real and not a simulation or illusion.

Sentience of other beings: Other animals are conscious and can feel pain.

An ethical hierarchy: Believes that not consuming other organisms is the most ethical, followed by veganism, then vegetarianism, with omnivory/carnivory being the least ethical.

Atheism and materialism: Gods, souls, reincarnation, and resurrection do not exist. Life is a product of evolution, not creation.

Lack of free will: Human will is determined by genes, environment, and experiences.

The author explicitly states that the reason these are only "almost certain" is the philosophical possibility that reality could be a simulation, dream, or illusion, making absolute certainty about the external world impossible. They identify this agnostic stance as the reason for their uncertainty.

[Compassionist]

[Replying to William in post #9]

William, the summary you provided is broadly accurate as a descriptive outline of my post, but it restates rather than challenges it. My central argument isn’t simply a list of facts - it’s about epistemic grounding: what can a conscious being know with absolute certainty, as distinct from probabilistic inference.

I hold that only immediate self-awareness (“I am conscious”) qualifies as completely certain, because all external claims - about bodies, universes, gods, or simulations - depend on perception and interpretation, which can be mistaken. Everything else, no matter how plausible, remains almost certain, not absolutely certain.

So my interest isn’t in asserting beliefs as data points, but in clarifying the logical boundary between direct phenomenological certainty and inductive near-certainty.

If your intention in sharing the AI summary was to explore that boundary, I’m happy to continue there. But if the goal was to evaluate my worldview as information rather than argument, I’d suggest we now turn to the philosophical question itself:

What, if anything, can consciousness know that is immune to error, illusion, or simulation?