How much evidence does it take to believe or to know?

[Pastabake]

I'm sure there is an equation that encompasses scepticism, cynicism and gullibility ... in relation to the numbers of people that already believe.

Initially almost no evidence will be required for at least one individual to believe in something ... until almost all believe. Mass belief in something is akin to mob mentality, once you get to critical mass people don't believe because there is good evidence to do so, they believe because everyone else does ... then for at least one individual no amount of evidence could make them believe.

This individual, like the first believer, is the seed of the counter belief ... not in the sense that they are a messiah/guru figure ... such people are almost always johnny come lately's cashing in on what is already there rather than being true visionaries .. their only vision tends to be what they can make out of it. Jesus and Buddha being prime examples.

I suspect that there is a evolutionary mechanism for this that ensures that we don't all go running off the cliffs to our deaths however plausible the reasons to do so might be.

What I guess I'm saying is that the vast majority of people require no evidence at all to believe in the majority of things they believe in. More so I'd claim that most rationalisations for said beliefs are almost always post hoc justifications.

[Londoner]

"How much evidence does it take to believe or to know?"

I don't think we ever assert 'belief' or 'knowledge' in the abstract, so there is something of a straw man in the question. We are all aware that there is no ultimate proof available for anything.

Instead, such terms are understood according to the context. If I 'know that Jesus loves me', everyone gets that this means something different to my knowing the boiling point of water or believing that the earth orbits the sun, or that the prisoner is guilty as charged. Similarly, the degree of certainty that goes with any claim of 'knowing' something is also understood according to context. If it isn't - for example if I claim I know Jesus loves me because he wrote me a letter, or that I have verified the boiling point of water through instinct, then this would provoke a discussion because this isn't the usual context for such claims.

So it's not 'How much evidence?', rather it is 'What sort of evidence?', the answer being 'That varies depending on the subject'.

[boagie]

Experience and understanding are the instruments, the quantity of time required to know depends on the objective content of the unknown.

[Philosophy Explorer]

Offhand I"d say the answer is it depends.

Statistics is often used to help decide. For myself I look for at least two independent ways to decide whether to believe like I did in a sales study and I was taught this in synthesizing chemical compounds.

[Elindeque1992]

I think experiencing it is the best bet.

[Michael_H_]

I would like to start a 'new' answer, if I may.
I think there is a difference between knowing and believing. Knowing is sometimes defined as ' true belief'. Certainly some of our beliefs may be true, but we can never know which ones, so this makes no sense. When the skeptic tells us that we can "never know anything for certain!", they are right, but it is a hollow victory. The question is really: when are we justified in believing something, or better, to act as though we believe it. And this may not require much 'evidence' at all. Suppose that you and a friend are driving to a party and you come to an intersection and don't know which way to turn. Your friend says, "I'm really not sure, but I think it might be ..left?" Could there be any more feeble evidence than this?! And yet, why would you decide to turn right, instead. You would go left, surely. Because, you have more reason to believe that than not. No one is suggesting that we 'know' which way the party is. Or even that we need to believe it. But we ARE justified in acting as though we believe it. And that seems to be about as close as we can get.
In short, yes we need evidence of some sort, one way or the other. But our justification is just that we have some reason to believe, until something happens that gives us reason NOT to.
Or something like that.

[Pattern-chaser]

I would like to start a 'new' answer, if I may.
I think there is a difference between knowing and believing. Knowing is sometimes defined as ' true belief'. Certainly some of our beliefs may be true, but we can never know which ones, so this makes no sense. When the skeptic tells us that we can "never know anything for certain!", they are right, but it is a hollow victory. The question is really: when are we justified in believing something, or better, to act as though we believe it. And this may not require much 'evidence' at all. Suppose that you and a friend are driving to a party and you come to an intersection and don't know which way to turn. Your friend says, "I'm really not sure, but I think it might be ..left?" Could there be any more feeble evidence than this?! And yet, why would you decide to turn right, instead. You would go left, surely. Because, you have more reason to believe that than not. No one is suggesting that we 'know' which way the party is. Or even that we need to believe it. But we ARE justified in acting as though we believe it. And that seems to be about as close as we can get.
In short, yes we need evidence of some sort, one way or the other. But our justification is just that we have some reason to believe, until something happens that gives us reason NOT to.
Or something like that.

Welcome to the forum, Michael!

This is a balanced and considered post, and I can see little to dispute. Uncertainty is not an excuse or a reason to do nothing; to believe, know, or assume, nothing. We need to take what we have, incomplete or inadequate though it may be, and work with it, because "it" is all we have. As a species, we have done quite well by doing exactly this, I think. Well said!

Perhaps the only caveat is that we should, ideally, be aware that we are working with guesses and assumptions, to avoid the pitfall of thinking our guesses are more justified than they really are.

[Lagayscienza]

There are different ways of knowing. Deduction and induction are the usual and most reliable ways but sometimes all we have is abduction or inference to the best explanation - like in your decision about whether to turn left or right on the way to the party scenario. Abduction is like a best guess. It lacks strong evidence and is more likely to be wrong than deduction and induction but sometimes it's the best we can do.

[Michael_H_]

Thanks Pattern-chaser - just joined this site and looking forward to exploring.
Good point that we need to be cautious - the big thing about strength of evidence is what are the consequences of being wrong! If I get the party directions wrong I can just turn around and go back but if I'm heading into a war zone.. might want to be more careful!

[Michael_H_]

Lagayscienza,
I hadn't heard the term 'abduction' but we obviously use 'best guess' a lot! And the degree of required caution can vary.
I know that deduction is said to be a way to logically derive truth, but while a deduction may be valid, its truth still relies on the truth of its premises. So you kind of end up in the same position as you were. But having some nice strong premises is a good place to deduce from!
Induction is weird because it's completely invalid, formally - "The sun will (probably) rise tomorrow because it always has" appears to be utter nonsense, but it's ultimately based on the way we 'know' or observe the world to work and is very powerful.

[LuckyR]

I would like to start a 'new' answer, if I may.
I think there is a difference between knowing and believing. Knowing is sometimes defined as ' true belief'. Certainly some of our beliefs may be true, but we can never know which ones, so this makes no sense. When the skeptic tells us that we can "never know anything for certain!", they are right, but it is a hollow victory. The question is really: when are we justified in believing something, or better, to act as though we believe it. And this may not require much 'evidence' at all. Suppose that you and a friend are driving to a party and you come to an intersection and don't know which way to turn. Your friend says, "I'm really not sure, but I think it might be ..left?" Could there be any more feeble evidence than this?! And yet, why would you decide to turn right, instead. You would go left, surely. Because, you have more reason to believe that than not. No one is suggesting that we 'know' which way the party is. Or even that we need to believe it. But we ARE justified in acting as though we believe it. And that seems to be about as close as we can get.
In short, yes we need evidence of some sort, one way or the other. But our justification is just that we have some reason to believe, until something happens that gives us reason NOT to.
Or something like that.

In this context we're discussing definitions of words first, then how they relate to concepts. In my understanding of the wording, there are things that are knowable, for example: what did I have for breakfast yesterday and there are things that are unknowable, for example: do gods exist. Belief is used to describe the situation when things are unknown, either because they are unknowable or if the individual merely happens not to know (a completely knowable) piece of information. Thus I can know (or not know) what you had for breakfast, if I don't know, I can believe you had pancakes, perhaps because I see a plate in your sink which has the dregs of pancakes on it. Whereas in the case of gods, I can believe or not believe they exist, but I cannot know they exist (despite the protestations of the devout).

[Lagayscienza]

Lagayscienza,
I hadn't heard the term 'abduction' but we obviously use 'best guess' a lot! And the degree of required caution can vary.
I know that deduction is said to be a way to logically derive truth, but while a deduction may be valid, its truth still relies on the truth of its premises. So you kind of end up in the same position as you were. But having some nice strong premises is a good place to deduce from!
Induction is weird because it's completely invalid, formally - "The sun will (probably) rise tomorrow because it always has" appears to be utter nonsense, but it's ultimately based on the way we 'know' or observe the world to work and is very powerful.

Yes, if deduction is the gold standard, then I guess induction is the silver standard. In many cases we would be silly to discount induction. Your example of the sun coming up tomorrow is a good illustration of this. Someone might want to argue that because we cannot know with 100% certainty that the sun will come up tomorrow, we ought rightly be agnostic on the issue. But that would be pedantic nonsense which we would be more than justified in ignoring. When it comes to something like the assertion that all swans are white, we need to be more cautious with induction.

[Belinda]

Lagayscienza,
I hadn't heard the term 'abduction' but we obviously use 'best guess' a lot! And the degree of required caution can vary.
I know that deduction is said to be a way to logically derive truth, but while a deduction may be valid, its truth still relies on the truth of its premises. So you kind of end up in the same position as you were. But having some nice strong premises is a good place to deduce from!
Induction is weird because it's completely invalid, formally - "The sun will (probably) rise tomorrow because it always has" appears to be utter nonsense, but it's ultimately based on the way we 'know' or observe the world to work and is very powerful.

Yes, if deduction is the gold standard, then I guess induction is the silver standard. In many cases we would be silly to discount induction. Your example of the sun coming up tomorrow is a good illustration of this. Someone might want to argue that because we cannot know with 100% certainty that the sun will come up tomorrow, we ought rightly be agnostic on the issue. But that would be pedantic nonsense which we would be more than justified in ignoring. When it comes to something like the assertion that all swans are white, we need to be more cautious with induction.

The Sun coming up tomorrow fits a frame of how moderns understand that the Solar System behaves. Therefore we presume the Sun's coming up tomorrow is a law of nature. Laws of nature or of necessity are basic to the theory of existence called Monotheistic Pantheism.

That frame of belief was not always so. Many peoples used to believe that the Sun's behaviour depended on how people behaved ; people had to certain rituals before they could safely predict the Sun. This was not Pantheism as it was a belief the Sun was a god in its own right which/who may require to be propitiated and was not subject to an absolute law of nature/Nature.

Deductive logic is a method of reasoning similar to mathematics.

[Samana Johann]

Standard of Belief

First of all, this thread is not about opinions (e.g. the sky is pretty, or this cake tastes good). It is completely logical that opinions differ from person to person.

This thread is about factual statements and the standards we use to determine whether or not to believe them.

How much evidence does it take for you to believe something as opposed to just thinking it is possible? (e.g. "I believe the sky is blue" as opposed to "The sky may be blue or not; there is not enough evidence for me to believe one way or the other.")

How much evidence does it take for you to say that you know something? (e.g. "I know the sky is blue," or "I know the sky is not blue.")

How much evidence is required against something for you to not believe it is possible? Do you just have to believe the opposite? (e.g. "I believe the sky is blue, so I think it is not possible that the sky is not blue.")

Every effort, unless knowing the truth, as things arise and decay, is always based on believe. If one is good aware, then at the moment of touch, there is knowing, yet also gone right there.

Naive to believe the sky is blue, good householder. And what's blue? What's good householders perception of blue and sky.

[Lagayscienza]

Lagayscienza,
I hadn't heard the term 'abduction' but we obviously use 'best guess' a lot! And the degree of required caution can vary.
I know that deduction is said to be a way to logically derive truth, but while a deduction may be valid, its truth still relies on the truth of its premises. So you kind of end up in the same position as you were. But having some nice strong premises is a good place to deduce from!
Induction is weird because it's completely invalid, formally - "The sun will (probably) rise tomorrow because it always has" appears to be utter nonsense, but it's ultimately based on the way we 'know' or observe the world to work and is very powerful.

Yes, if deduction is the gold standard, then I guess induction is the silver standard. In many cases we would be silly to discount induction. Your example of the sun coming up tomorrow is a good illustration of this. Someone might want to argue that because we cannot know with 100% certainty that the sun will come up tomorrow, we ought rightly be agnostic on the issue. But that would be pedantic nonsense which we would be more than justified in ignoring. When it comes to something like the assertion that all swans are white, we need to be more cautious with induction.
The Sun coming up tomorrow fits a frame of how moderns understand that the Solar System behaves. Therefore we presume the Sun's coming up tomorrow is a law of nature.

Yes, it fits with the modern scientific view of the Solar System. However, it is still a case of induction because it is conceivable that the sun may not always come up - the earth might be bumped out of it's orbit by a passing star, for example, which would also be within the laws of nature.

Laws of nature or of necessity are basic to the theory of existence called Monotheistic Pantheism.

And to Materialism.

That frame of belief was not always so. Many peoples used to believe that the Sun's behaviour depended on how people behaved ; people had to certain rituals before they could safely predict the Sun. This was not Pantheism as it was a belief the Sun was a god in its own right which/who may require to be propitiated and was not subject to an absolute law of nature/Nature.

Yes, back them people had what might seem to us today to be some funny, but understandable, ideas.

Deductive logic is a method of reasoning similar to mathematics.

Like mathematics, Deduction follows logical steps, and it has a formalism that I guess can make it look a bit mathematical.