Why do we need the concept of knowledge, not just beliefs?

Why do we care if something is "real" or not?

Because if tiger is real and the roar nearby means a tiger, and you won't care, you won't pass your genes to the future generations.

People who didn't really care about aligning beliefs with reality at least on basic level were wiped out by natural selection. And genes of more sensible people were passed on.

If a person A’s beliefs coincide with a certain aspect of all other people’s beliefs (or the beliefs of the people around her in her era) in a certain way, her life will as a result changes in a certain way different from person B. I don’t see how “knowledge” in particular has any particular effect on her life.

You can be perfectly well socially adapted, going to the same church as everyone else, but if you eat random mushrooms you find or ignore traffic rules, your chances of dying are still high. Social adaptation isn’t enough.

Because knowledge adds a success condition: it’s what separates lucky guesses or convenient fictions from beliefs that genuinely help us navigate the world. That’s why science and technology advance through knowledge, not just shared belief

For some reason, we have found it useful to try to identify when beliefs are likely to correspond with the world. I suspect this is because animals that believe real things are more likely to reproduce, and eventually this endeavour became fulfilling for its own sake and an integral part of our society. But this paragraph is more about psychology or evolution than philosophy.

If we speak only of beliefs and not also about justification and truth, then we lose much of the basis on which we debate. The entire endeavour of belief revision becomes ungrounded. Science would have no goal. We would be satisfied holding many false beliefs and would not even have a concept to identify them as such.

Consider that someone believes X but the world is not X. If that situation seems incongruent at all to you, then you need to reach for concepts of justification and truth.

If you have no preference for whether your or anyone's beliefs correspond with the world or with other beliefs they hold, then sure, ignore justification and truth. But you will be removing yourself from the dominant conversation of our societies.

The issue with (unqualified) belief is that it can be misleading and unreliable. For example, everyday observation would lead us to the belief that the sun is an object roughly the size of the moon, which rises and sets with respect to a flat and static earth. This is (for most practical purposes) a perfectly fine belief, but maintaining it creates definite problems within certain specialized fields. I mean, how could we envision geostationary satellites (like those used for GPS) if we hold that the Earth is flat and static? So we end up reasoning this way:

1. Beliefs based on immediate appearances, while indisputable, are often unsatisfactory for specific purposes…
2. Different beliefs can be constructed which are more generally functional even if they seem unintuitive, and finally…
3. There is some principle (separate from beliefs) that governs the way things are, and we want our beliefs to approximate whatever that principle is.

In this way we get to a notion of 'truth' distinct from 'belief', and also to a notion of 'knowledge', which is a type of belief that approaches truth.

However, we have to keep in mind that possession of 'truth' is a locus of social power, and so 'knowledge' is a constantly contested arena. Sometimes this is innocuous enough, as when people argue over the comparative utility of differing theories. That kind of dispute leads towards philosophical and scientific advancements, which is often (though not always) for the good. But sometimes 'truth' becomes a matter of declaration, not pragmatism, turning it into a pure form of social power. This — while not intrinsically bad — can create all sorts of social problems through the struggle to attain and maintain that power.

The motivation behind 'justified true belief' and similar efforts to validate knowledge-as-truth is mainly to rein in the more noxious manifestations of knowledge-as-power. We don't necessarily want people to rely on mere belief (aka opinion); that leads to an unproductive mess of conflicts between those who believe different things. We also don't necessarily want people asserting knowledge-as-truth as a mere social power gambit; that leads to an unproductive mess of conflicts between those competing for power.

Knowledge affects people's lives, directly and indirectly. Someone may earnestly believe the earth is flat and static, but if they use GPS through a mapping app they are pragmatically relying on a knowledge that they do not believe is true, which is philosophically untenable. The hope is that we can leverage those areas of philosophical untenability to reach knowledge that does approach true principles. Simply believing isn't sufficient to that end.

If you are asking why the word knowledge exists when, in practical terms, it is equivalent to high-confidence belief... The same reason most words exist: it is convenient to be able to convey the concept briefly.

Most people do want to distinguish beliefs that they are reasonably certain are essentially correct from those they are less certain of. I "know" that I am writing this answer; there are some extreme scenarios which would falsify that, and there may be detail which could be added about how those words are interpreted, but as far as I can tell the statement is accurate enough for all practical purposes.

I don’t see how knowledge has any particular effect on our history

Our pursuit of knowledge through science has produced: (just off the top of my head)

• Knowledge of germ theory, which reduced related infection and illness from exceedingly common and deadly to rather rare.
• Knowledge of biology and chemistry, which led to the development of medical treatments that have saved countless lives.
• Knowledge of weather patterns, which allowed us to detect and predict the movement of deadly storms, which enabled us to saved many lives through issuing warnings and evacuation orders (never mind predicting longer-term weather patterns, AKA climate).
• Knowledge of electricity and the functioning of various components, which has led to the creation of every electrical appliance that exists, including computers, as well as the internet, which has helped humanity achieve many good things (but also some bad things).
• Knowledge of plants and nutrition, which allowed us to grow and process food safely and effectively (even if companies also exploited this knowledge to make unhealthy addictive food).

Beyond that:

• Knowledge of people suffering enables us to take steps to prevent that suffering.
• Knowledge of how economic and legal systems function enables us to optimise these systems for the good of humanity. Knowledge about and concern for these systems have been lacking among the public for practically all of human history, which has allowed people in power to exploit these systems for their own benefit, to the detriment of the public.

Prior to gaining knowledge in every case above, entire communities had false beliefs or lacked beliefs about these things. So aligning one's beliefs with people around you would not in any way have led to gaining the knowledge above or gaining the corresponding benefits.

Knowledge is exceedingly useful in helping you achieve whatever goal you're looking to achieve. Yes, this unfortunately includes any malicious goals someone might have, but it seems that most people have noble goals, even if they're misguided in those and thus end up causing harm (which would thus be due to a lack of knowledge). So increasing knowledge generally does more good than harm.

If your stomach hurts and you want to stop that, it's very useful to have knowledge about what's causing your stomach to hurt, whether that's hunger or food intolerances or illness, and to have knowledge about what would cause it to stop hurting.

If you have some false belief about why your stomach hurts or you have no idea why it hurts (i.e. you lack knowledge about that), you may very well end up doing things that make your stomach hurt more.

This same reasoning applies at every scale, from helping you as an individual achieve your goals, to helping the group of people in a community, city, country or the world as a whole, achieve their collective goals.

If we merely concern ourselves with beliefs, and not knowledge, this doesn't give any of the above benefits of pursuing or obtaining knowledge.

Other answers (and, in fact, the OP) already shows that there is a difference in our intuitive definitions of Knowledge and Belief which is at least partially based on Truth. I won't reiterate those answers, but since the OP asked for things to read about:

Defining Knowledge as a special type of Belief is not the only solution. It has been shown that JTB needs some extras to make it less fallible in some cases, but those additions tend to be complicated or cause other issues. Instead of giving up and saying that there is no reason to differentiate, we could use a kind of Knowledge First Epistemology, where Knowledge is its own simplest form. What if Knowledge isn't a supreme kind of Belief, but Knowing just causes you to Believe it too. Perhaps Belief is just an approximation of Knowledge (the example I was given is "roundness" being an approximation to "circular"). Perhaps Believing something is treating something as if you Know it even though you don't. Perhaps Belief and Knowledge are just different kinds of mental state. There are clearly various other options here.

Or, for a different approach entirely, read up about Virtue Epistemology. Continue to avoid worrying about how to define Belief vs Knowledge by stating that Knowledge is a JTB arrived at through a "virtuous thought process". Then we can stop defining the results and start defining what we should be doing when we think. What makes a thought process "virtuous"? What are good traits to have when we go through an intellectual process? What should we avoid? How do we use this to change our behaviour as individuals and as a collective?

Because it would be irrelevant

Why do you think it matters what you or anyone else believes?

Nothing matters unless it has (or potentially has) utility. We can't foresee which true facts will never be useful, of course, so let's preempt value judgements by assuming that all true facts have utility.

But then you've discarded the wrong part of the phrase. You haven't given equal billing to all true facts; instead you've given equal billing to true facts, mistakes, and perhaps even outright lies.

An important definition of "belief" here is

confidence in the truth or existence of something not immediately susceptible to rigorous proof.

No-one can (absent some intervention by hypothetical gods) magically arrive at truth immediately. Whether personally or (via the scientific process) as a society, arriving at truth is a process of evaluating potential candidate hypotheses. Each hypothesis can be believed, but it is not truth until it has been evaluated against the real world. At that point the belief, which was without sufficient proof, is no longer merely a belief but becomes knowledge.

Even more rigorously though, it's valid to say that whilst something may be considered "knowledge" in one environment, extrapolating that to other environments is still a "belief". Newtonian physics is a good example - it proved perfectly adequate for physics on Earth, but extrapolation to planetary physics showed that a better version existed. But even Newtonian physics demonstrated that Archimedean physics was false. This is a good demonstration of utility, because belief in Archimedean physics prevented correct analysis of the motion of systems. Newtonian physics might have been flawed, but it was (and is) still sufficient to achieve that. Einsteinian physics might also be flawed - look up "dark matter" and "dark energy" - but it's still sufficient to work out planetary motion and GPS positioning.

You ask:

Why do we need the concept of knowledge, not just beliefs?

Strictly speaking we do not need the concept of knowledge at all, and many people seemingly work hard to avoid the work of justification relying on beliefs ignorant of their inconsistency with empirical evidence and logical consistency. But appealing to facts about the world and reason when formulating new beliefs is the classic understanding about knowledge: justified, true belief. By examining our thoughts, we can make our picture of the world more consistent with our experiences and actions.

What advantage, then does the concept of knowledge have over mere belief? It allows us to exercise our judgement to decide which beliefs are better and more effective at getting us what we want. For instance, medical knowledge is far better at curing disease than pseudoscientific theories such as superstitions, homeopathy, or chiropractric "medicine". This is because scientific thinking and rigorous epistemology generate facts.

Thus, we can think of knowledge as a type of belief that is more accurate and more reliable than intuition or rumor or dogma. This is because knowledge is the production of a process in which beliefs are tested by physical and rational processes. The very idea that some beliefs are more reliable than others can be studied in more detail by reading this article on reliabilism (IEP). From the IEP:

Reliabilism encompasses a broad range of epistemological theories that try to explain knowledge or justification in terms of the truth-conduciveness of the process by which an agent forms a true belief. Process reliabilism is the most common type of reliabilism.

In other words, certain ways of thinking and doing regularly produce beliefs that help us achieve our goals and have a beneficial effect on society.

We talk about “knowledge” because it’s the extra step that lets us separate lucky guesses from things we can actually rely on. A belief can be true, false, or just a gut feeling—think “I feel today will be a good day.” Knowledge, on the other hand, demands that the belief be true and that we have good reasons or evidence for it. That extra layer of justification is what lets us build dependable systems, make sound decisions, and trust each other’s claims.

In everyday life we can’t get by on unchecked opinions alone. When a doctor prescribes a treatment, a engineer designs a bridge, or a scientist publishes a result, we need to know that the underlying belief is backed up by evidence and reasoning—not just a personal conviction. So the concept of knowledge is what lets us move from “I think” to “I know,” and that makes cooperation, progress, and safety possible.

Then how do we talk about those things that we now take as beliefs?

If you would ask me was did the sun set to west yesterday I would say yes, but it would just be a belief in my memory of yesterdays sunset. I could remeber wrong.

While technically you can say we are in a dream and maybe yesterday did not exist in this dream. So yes, "truths" are "beliefs", but if we have to reconsider this in everything we do it becomes unecessary because it is a dead end or it solves itself.

Either we say whatever could have happened yeserday and thats that, or we focus on what likely happened and have a more meaningful things come out of our thinking.

As you have noted it is common for philosophers to say that knowledge is justified true belief. It is also common for people outside philosophy to hesitate to say they have knowledge. Following Karl Popper I don't think real knowledge is justified, a lot of it isn't true and almost none of it is belief.

Justification is an alleged process that shows an idea is true or good or has some measure of truth or goodness. No such process exists. An argument uses assumptions and rules that are supposed to produce true results when applied to true assumptions. Your rules and assumptions are either correct or incorrect and there is no way of guaranteeing their correctness or showing they are probably correct. People make mistakes and there is no way of preventing all mistakes. If you think a rule is correct you might not have found a case in which it is wrong but you have no way of knowing whether or when or where such a case will turn up. And you access to facts is in general dependent on such rules, e.g. - experimental results in physics are dependent on your understanding of how the equipment works and on your understanding of the processes by which information is conveyed from the system being measured to that equipment.

A lot of knowledge isn't true. Newtonian mechanics is useful for doing some calculations and understanding some processes but it is false as a description of reality. The same is true of general relativity and quantum theory since they are incompatible and both are used to understand different aspects of how the world works.

Knowledge is also mostly not beliefs. There are many books, computer programs and other artefacts that contain knowledge no person has in his head.

Knowledge is information that can be used to solve some problem that may be practical or experimental or theoretical or moral or any other kind of problem that seems worth solving. Instead of looking for justification to decide whether to use some item of knowledge we can look for problems instead. If there is some known problem with using a piece of knowledge you try to solve that problem by proposing new ideas and criticising them according to whether they solve problems. If a piece of knowledge solves some problem and there are no known problems with it or alternatives to it then you can use it. This was pointed out by Karl Popper, see the readings here

https://fallibleideas.com/books#popper

See also

https://criticalfallibilism.com/

In a real situation if you want to know whether to use a piece of knowledge you look at what problems it solves, whether those problems are relevant and whether that knowledge has any known relevant problems. Using any old idea that somebody happens to believe is a bad idea because it may not solve the problem you're interested in and it may have problems you could easily work out by doing a literature search or looking for criticisms of the idea yourself.

You specifically asked in a comment why the "justified" part is useful. So here's another answer including that one.

In the concept of knowledge as justified true belief,

• "True" is useful because it means that the belief reflects physical reality; this in turn means that actions you take based on said belief are of a higher probability to increase your chances of success. Example, stolen shamelessly from another answer: "This mushroom is not poisonous." It would be very useful if this belief were true.
• "Justified" is useful because it distinguishes the JTB from a only-true-but-not-justified-belief that is just randomly happening to match reality, without the believer having any clue why that may be the case (examples of this would be rote knowledge learned in school where only the fact itself was taught, not the reasoning behind it - assuming the justification "because teacher said so" is weak). Being justified means the belief was reasonably arrived at; it means there is some kind of recipe or validation that you can follow to check a possible new statement to see how likely it is to be true, and so on and forth. Think about it like the concept of Falsifiability in the Scientific Method - both have similar goals.

Knowledge is at foundation of our actions, while beliefs is the precursor of our reasoning.

Therefore, the relation between beliefs and knowledge is parallel and comparable with the dynamism between reasoning and actions.

Well, consider "I know that the weather will be sunny tomorrow" (knowledge) versus "I believe the weather will be sunny tomorrow" (believe):

From a scientific point of view one could say that knowledge is a subset of believe (not all that is believed is known (or true)), so believe is more common than knowledge. So maybe it could have a larger influence even.

From a sceptic point of view one could say that believe is a subset of knowledge (not all what is claimed to be true is believed). For example science has claimed that atoms are indivisible for some time, then it turned out that it's not true.

One could also say "the unproven" instead of "believe", meaning that there are things known to be true, and things that are known not to be true. Everything else is open to "believing or not".

Believe has less certainty than knowledge has (not I'm not saying that knowledge is absolutely certain).

Consider someone (maybe on LSD) believing he can fly, opposed to a normal being: Who would jump out of a window in the 20th floor, and which belief would last longer eventually?

Courtesy of @Geoffrey Thomas

See Plato, Meno, 97A:

Socrates Hence true opinion is as good a guide to rightness of action as knowledge; and this is a point we omitted just now in our consideration of the nature of virtue, when we stated that knowledge is the only guide of right action; whereas we find there is also true opinion. Meno So it seems.

Socrates Then right opinion is just as useful as knowledge. Meno With this difference, Socrates, that he who has knowledge will always hit on the right way, whereas he who has right opinion will sometimes do so, but sometimes not.

And see Plato on Knowledge in the Theaetetus:

Plato's Third Definition: [201d–210a] Theaetetus’ third proposal about how to knowledge is that it is true belief with an account (meta logou alêthê doxan).

The common view about Knowledge as Justified True Belief is that the truth condition is essential because one can only know things that are true.

Truth is a metaphysical, as opposed to epistemological, notion: truth is a matter of how things are, not how they can be shown to be. So when we say that only true things can be known, we’re not (yet) saying anything about how anyone can access the truth.

But contra, see Graham Harman, On Truth and Lie in the Object-Oriented Sense (Open Phil, 2022):

It seems to me that knowledge ought to be defined simply as “justified belief,” or perhaps even as “justified untrue belief.” Seekers of knowledge are essentially seekers of justification, not of truth. [...] Knowledge must be justified, but it can never be true, since there is no direct access to the real. To say this we need not be Kantian believers in the thing-in-itself, but need only believe in the ongoing advent of scientific and philosophical revolutions, which have already occurred often enough. This is the respect in which the scientific mainstream of any given era can be said to have knowledge, despite the eventual overthrow of most or all of what it thinks it currently knows.

This is at odds with the previous analysis, but we can find a common point: according to traditional point of view, truth is metaphysical but science is not involved with metaphysics ("seekers of knowledge are essentially seekers of justification, not of truth").