Handbook of epistemology/Justification and evaluation of knowledge

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The problem of the recognition of knowledge[edit]

To know we must know that we know. Having a true representation is not enough. We must be able to recognize that it is true, we need criteria for the recognition of knowledge that show that our representations are true. But very generally we do not know if what we think or what we are told is true or not. We may even doubt our own observations and memories, because they are sometimes erroneous. We do not have a universal and infallible device for the detection of knowledge. We are often mistaken. Very generally we do not know the difference between knowledge and ignorance. It is then tempting to conclude that we never know how to recognize knowledge, and that therefore we never know anything, since we must know how to recognize knowledge in order to know.

Is not the requirement for the recognition of knowledge itself a mistake (Sextus Empiricus)? Would not there be a regression to infinity? To know we must know that we know, therefore we must know that we know that we know, and so on to infinity. If we propose criteria for the recognition of knowledge, how do we know that they are not erroneous? Should there be other criteria of knowledge to recognize them as good criteria of knowledge? And so on to infinity?

To justify our claims to knowledge, we use evaluation systems that define ideals of knowledge. Is then considered a true knowledge, a justified one, what reaches our ideals, or what is close to them. The recognition of knowledge and is thus based on an ethical knowledge. We recognize knowledge by recognizing that it is what it should be, or that it is desirable. But how do we know that our ideal determines a real knowledge? It could be nothing but an illusion to make us feel good, to reassure us and flatter our vanity. And our so-called knowledge, based on such an illusion, could be just as illusory and completely devoid of truth. The ideals are not more real than dreams. It may seem absurd to establish the true knowledge, the knowledge of truth and reality, on a dream.

We can give us many ideals of knowledge that contradict each other. What is considered a good knowledge by one may be despised by others. Which ideal should we choose? How to recognize that an ideal of knowledge is a good ideal, that it does not despise good knowledge and does not honor ignorance? To recognize that it is a good ideal we must justify it from an ideal of knowledge of the ideal. But this ideal of knowledge of the ideal must also be justified. Is there not an infinite regress?

To justify our claims to knowledge we give reasonings designed to prove their conclusions. An affirmation is justified when it is the conclusion of a good reasoning. The existence of a rational proof is taken as a knowledge standard. But is it really a good standard? Do we really need to know that all men are mortal and that Socrates is a man to know he is mortal?

To recognize knowledge by reasoning we must first be able to differentiate between good arguments and others. But how to recognize good reasoning? How to distinguish them from fallacies and ratiocinations which prove nothing?

A reasoning establishes the truth of its conclusion from the truth of its premises. To conclude, we must know in advance that the premises are true, hence we must justify the premises. Should we look for other reasonings to prove them and so on to infinity? But then our reasonings would never be conclusive because they would always be based on unwarranted assumptions.

These skeptical objections are not as formidable as they seem. To be convinced one just has to consider how we recognize, justify and evaluate the various forms of knowledge.

The silent recognition of knowledge[edit]

We have natural faculties of knowledge recognition. Except in cases of hallucination, we make the difference between perceptions and memories on the one hand and fictions on the other. Similarly we distinguish good, clear and precise perceptions from bad ones (because the scene is too far, or because there is not enough light, or because the noise prevents hearing ...). We recognize a confused recollection, when it is too old, or deformed by subsequent memories, or by too intense emotions. We distinguish uncertain expectations or inferences from what past experience has well confirmed. We recognize a good skill when it reaches always, or very often, its objectives. We also have natural faculties of lie detection. Many signs (tone of voice, face, body language) help us to make the difference between a liar and a reliable witness.

Recognition of knowledge is an evaluation. It defines an ideal of knowledge. Our natural faculties point us towards an ideal of accuracy of observations, of efficiency of skills, of truth of inferences, expectations and talks. Should we doubt these ideals? Do they lead us to despise good knowledge and honor ignorance? Of course not.

We naturally know how to recognize knowledge, at least at times, but the ways we recognize it are not infallible. Although perceptions or memories seem clear and precise, they may be wrong. Previous experience is not always enough to recognize the truth of inferences or the efficiency of skills, because it can be contradicted by subsequent experience. A liar if good actor knows how to hide his lies.

Our observations are sometimes wrong. We are deluding ourselves and we do not always realize it. Since our perceptions sometimes deceive us, since they sometimes show us things as they are not, could it be that they always do so and that we live permanently in a world of illusions ? As for the knowledge acquired by the testimony of others, it is even worse, because in addition to their illusions they can deceive us with lies.

Our natural faculties of knowledge recognition are not infallible but there is no reason to believe they are always wrong. There are rather good reasons to believe that they are often quite reliable. Our observations generally enable us to choose a behavior adapted to reality. The adaptation of our actions to perceived objects is a verification of the correctness of our perceptions, of the adequacy of our internal models to the reality they represent. When our observations deceive us, we can correct them with better observations. We can always improve the reliability of our knowledge recognition devices. From this point of view, the problem of observation error is not a problem of principle, but only a practical problem: how to observe in good conditions with good observation devices?

Justification of knowledge[edit]

Knowledge justifying standards[edit]

What we spontaneously recognize as knowledge depends on our experience. Since individual experiences are always different, we should not expect the knowledge spontaneously recognized by some to be so recognized by others. When we communicate knowledge, we must expect skeptical reactions and we have to respond and justify our claims to knowledge. When we say what we know or think we know, we must be able to say why it should be recognized as knowledge. We do this with an argument that always has the same form:

For all statements x, if x satisfies the criterion C then x is a knowledge, now A satisfies the criterion C, hence A is a knowledge.

We recognize knowledge with knowledge justifying standards, or criteria. Generally a statement is a knowledge when it is true and justified:

For all statements x, x is a knowledge if and only if x is true and justified (Principle 1).

The truth of this principle may be accepted by definition of knowledge.

One could fear that this approach exposes us to an infinite regress, because to conclude that a statement is a knowledge you have to know beforehand a justifying criterion, that this is a good criterion and that it is really satisfied by the statement to justify. If we always have to justify everything it seems that our justifications can never end. But this fear of infinite regress is unfounded. By examining how the various forms of knowledge are justified, we realize that certain statements are justified from themselves, that it is not necessary to justify them from another knowledge.

Justification of observations[edit]

- How do you know it?
- Because I saw it.
- Are you sure that you saw it?
- Yes. I saw it clearly.
- How do you know you saw it clearly?
- Because I saw it clearly.

A good observation can sometimes justify itself. When we have to justify it, we must say it's a good observation, but it is not always necessary to say why it is a good observation. When our natural faculties of perception lead to clear and precise observations, it is not necessary to seek further justification.

If we gave ourselves observation or perception as a knowledge standard, we would be exposed to error, because observations are sometimes wrong. However, if we demand that observations be good then we get an irrefutable principle:

If a statement is a good observation then it is true and justified (Principle 2), and so is a knowledge.

This principle is irrefutable because its truth can be allowed by definition of the concepts of good observation and justification. If an observation is not true then it is not a good observation, by definition of the concept of good observation. If it is a good observation, then it is justified by definition of the concept of justification.

The principle is irrefutable but its application is not infallible. Sometimes we delude ourselves when we think we recognize a good observation. Moreover we often have to justify that an observation really is a good observation. If we use observation devices, measuring instruments, detectors, other than those given to us by our natural faculties of perception, we must prove that they enable us to make good observations. But there is no infinite regress because some forms of knowledge are justified spontaneously by themselves.

The principle of the truth of good observations defines an ideal. To adopt this ideal is just to want good observations. But why adopt this ideal? The ultimate reason is simply that we want it. We voluntarily choose to welcome good observations in the field of knowledge. We do not want a purely abstract knowledge that ignores everything we live. Such commitment has a humanist meaning. We (humanist human beings) want all human beings to have an equal right to testify on behalf of knowledge as observers of the same world. We want that their observations be respected and authoritative, provided of course they are good observations.

Justification of empirical laws by observation[edit]

Inductive reasoning, which is to move from the truth of one or more observations to the truth of a law that summarizes them, is not logically correct. To be true an empirical law must be true for all the observations made in conditions where it is applicable, both all past and all future observations. As it is always conceivable that new observations contradict the laws that were previously well confirmed, the truth of a law can never be proved from observations, or at least not in an infallible way. That is why it is sometimes said, following Karl Popper (1934), that empirical laws are not verifiable, that they are only refutable.

To maintain that we can never verify empirical laws contradicts most common uses. When our empirical laws are confirmed by good experiences, they lose their hypothetical character and we expect them to be always confirmed, we do not doubt their truth any more. But for them to be well confirmed, we ask more than a few observations, we want well-controlled experiments. An experiment is well controlled when the experimenter knows precisely all the conditions that may affect the observed result. To make well-controlled experiments is often quite difficult, and more so if the observed system is very complex. From the point of view of the experimenter, the problem of verifying empirical laws does not conflict with a difficulty of principle but is only a practical problem: how to do well-controlled experiments?

Like the concept of good observation, the concept of well-controlled experiment leads to an irrefutable principle:

If an empirical law is fully confirmed by a well-controlled experiment then it is true and justified (Principle 3), and so is a knowledge.

This principle is irrefutable because it is true by definition of the concepts of well-controlled experiment and justification. If a law which were confirmed by a previous experiment was proven to be false after a subsequent one, then it would prove that the initial experiment was not well controlled. The experimenter did not control all the conditions that affected its result since the result has changed. If a law is confirmed by a well-controlled experiment then it is necessarily true, by definition of the concept of well-controlled experiment, and it is justified by definition of the concept of justification.

The principle of justification by well-controlled experiments is irrefutable but its application is not infallible. Sometimes we delude ourselves when we think we recognize a well-controlled experiment. Moreover it is often necessary to justify that an experiment is really well-controlled. We do this with prior knowledge that must itself be justified. But there is no infinite regress, because some forms of knowledge justify themselves.

Justification by reasoning[edit]

As soon as we know true and justified statements, we can take them as starting points for reasonings intended to increase our knowledge, because the existence of a rational proof is a criterion of justification:

If a statement is the conclusion of a logical reasoning whose premises are true and justified, then it is true and justified (Principle 4), and so is a knowledge.

This principle is true by definition of the concepts of logical reasoning and justification. If the premises of a logical reasoning are true then the conclusion is true, by definition of logical reasoning, and if in addition they are justified then the conclusion is justified, by definition of justification.

The simple communication of knowledge may lead to error, because of the variability of interpretations. A statement may be true in an interpretation and false in another. The same statement may be a knowledge for me, because it is justified and true as I interpret it, and an error for another, because he or she interprets it in a manner that makes it wrong. In a logical reasoning, the premises are sufficient truth conditions of the conclusion. Thus when we prove a conclusion, we clarify its interpretation. For the conclusion to be a knowledge, it must be interpreted in a way that respects the truth of the premises. Reasonings are useful not only to justify knowledge but also to remove ambiguities and dispel misunderstandings.

Justification of logic[edit]

We recognize a logical reasoning by verifying that it complies with logical principles. But how do we recognize the logical principles? How do we know they are good principles? How to justify them ? Are we really sure that they always lead to true conclusions from true premises?

By giving principles for the definition of truth (Tarski 1933), we can prove that our logical principles are true in the sense that they always lead to true conclusions provided the premises are true. One can even prove that a small number of principles is sufficient to determine all logical consequence relations (Gödel 1929).

A skeptic might object that these justifications of logical principles are worthless because they are circular. When we reason on logical principles to justify them, we use the same principles that we have to justify. If our principles were false, they would prove falsehoods and so they could prove their own truth. That logical principles enable us to prove their truth does not therefore really prove their truth, since false principles could do the same.

This objection is not conclusive. Just look at the suspected circular proofs to be convinced of their validity, simply because they are excellent and irrefutable. No doubt is allowed because everything is clearly defined and proven. A skeptic can point out correctly that such evidence can convince only those who are already converted. But in this case it is not difficult to be converted, because logical principles just formulate what we already know when we reason correctly.

The ultimate reason for logical reasoning is simply that we want it. As logical principles are universal, to respect them is to respect the reasoning faculty of all human beings and their equal right to give logical proofs and speak in the name of reason. We do not want a knowledge which would exclude logical reasonings, we want to welcome everything that reasonings can teach.

Justification of principles[edit]

Empirical, ethical and abstract theories are always based on principles (axioms and definitions) whose truth is accepted by definition of their terms. Such principles are very easy to justify:

If a statement is a principle whose truth may be accepted by definition of its terms then it is true and justified (Principle 5), and so is a knowledge (Descartes 1637, Pascal 1657).

A principle justifies itself provided it is true by definition of its terms. It is necessarily true, because it determines the interpretations that make it true.

With the principle 1, the principles 4 and 5 are sufficient to recognize the abstract knowledge: all abstract truths, so in particular all mathematical truths, as soon as they are proven. The five principles together are sufficient to recognize all true and justified statements, all such talking knowledge, empirical, ethical and abstract.

Evaluation of knowledge[edit]

The expression 'justification of knowledge' can be interpreted in several ways. In the preceding sections a statement is considered to be justified when it meets one of the knowledge justifying criteria, but that does not mean it has to be a very good knowledge. A statement may be true, justified and without interest, if it says nothing that deserves to be known. But to justify knowledge may mean also to show its value and importance. To avoid the ambiguity of the concept of justification, it is better in this case to speak of knowledge evaluation. Principles 1-5 are sufficient to justify knowledge but they are not enough to recognize good knowledge because for that we also need to evaluate it.

Evaluation of principles[edit]

« You will recognize them by their fruits. » (Matthew, 7:20)

« We shall see such demonstrations, which do not produce as great a certainty as those of geometry, and which even differ greatly from it, since instead the geometers prove their propositions by certain and incontestable principles, here the principles are verified by the conclusions drawn from them; the nature of these things not suffering that it be done otherwise. It is possible, however, to arrive at a degree of verisimilitude, which is often not much less than complete evidence, when things, which have been proved by these supposed principles, are perfectly connected with the phenomena which experience has pointed out, especially when there are many, and even more so when we form and anticipate new phenomena, which must follow from the hypotheses which are employed, and which we find that in this the effect corresponds to our expectation. If all these proofs of plausibility are found in what I have proposed to treat, as they seem to me to be, it must be a great confirmation of the success of my research, and it is hardly possible that things are not nearly as I represent them. » (Christian Huyghens, Treatise on light, p.2)

A priori, any set of formulas, if it is consistent, can be chosen to found an abstract knowledge. But we do not adopt any formula as a principle just for the pleasure of founding an abstract theory. We do not study all abstract theories that we can conceive. It would be futile, foolish and impractical. How then do we choose the principles of our abstract theories? More generally, how do we choose the truths by definition on which we base the empirical, ethical and abstract theories, with which we develop our knowledge? And how do we evaluate these choices?

We recognize good principles by their fruits.

A principle produces fruits when it helps us to acquire good knowledge. Not just any knowledge, not any true and justified statement. We want theories that make us really learned, that are more than a collection of true statements.

That a good principle produces fruits is a truth that can be accepted by definition of the concept of good principle.

We value the principles from the quality of the knowledge they enable us to acquire. A skeptic might expose a vicious circle: we justify our knowledge by proving it from principles, but we evaluate the principles from the knowledge they enable us to prove.

There is indeed a circle but it is not necessarily vicious. The principles are not the only source of knowledge. Observations and experiments, of the outside world and the inner reality, are also sources of knowledge. There is a circle because there is a constant dialogue between principles and their applications. Principles are intended to develop applications. They prove their value when we succeed. Failures however lead us to modify or abandon them. Principles are thus evaluated from their applications, their fruits, but the applications themselves are not evaluated only from principles. Perceptions, emotions and all that we live make us break the circle of evaluation of principles by principles.

The ideal of intelligibility[edit]

We seek a knowledge that makes the world and ourselves intelligible. We not only want to know true and justified statements. We want explanations.

We ask empirical theories to be confirmed by past observations and predict future observations, but this is not enough. We also want them to give us good explanations of what we observe. Predicting is not enough to explain.

We ask ethical theories to evaluate actions, behaviors, purposes, speeches ... but this is not enough. We not only want them to tell us what is desirable or mandatory, we also want them to tell us why, to explain their evaluations.

We do not ask only to abstract theory to prove theorems, we want them to enlighten us, to help us to understand abstract and concrete realities, to make them intelligible.

What is a good explanation? What does a theory need to enlighten or illuminate us?

Any knowledge that helps us to know a being, if only by analogy, can be considered as an explanation. But we ask more than that for reality to be intelligible. We want to be able to respond by reasoning to the questions we can ask ourselves. We want to know principles from which we can prove what we need to explain. However, any system of principles does not necessarily do the trick. Instead of enlightening us, it can make things even more obscure. What conditions must meet our principles to enlighten us, to make reality more intelligible?

We do not know very well. We can not know everything about it because science is innovative, because no one knows in advance the explanations it will discover. But we do have evaluation criteria that guide us in finding good explanations. Simplicity of principles, their generality, analysis of complexity , knowledge of ends, and sometimes theoretical beauty are the main criteria commonly invoked to evaluate our explanations. They apply equally to empirical, ethical and abstract knowledge.

Requiring simplicity of the principles is simply requiring that they be few and can be formulated in few words. Requiring their generality, is requiring that they be applied to a large number of individual cases. Such requirements may seem excessive and unrealistic. Why could the world with all its complexity be explained from a few simple principles? Individual cases are always different from each other. Why then should they all obey the same principles?

The ideal of intelligibility is sometimes associated with beauty, as a criterion of theory evaluation. Theories are asked to be beautiful, or to reveal to us the beauty of reality. This is not really a criterion because we do not know in advance what makes the beauty of theory or reality. But the desire for beauty is a powerful motivation for the pursuit of knowledge. It is a little surprising a priori. Why should reality be beautiful? Do we not believe in life in pink if we say that a theory must be beautiful to be true, or that it must reveal the beauty of the world? Yet the desire for beauty is not vain. Especially in theoretical physics (Albert Einstein, Paul Dirac), but also in all other sciences, the search for beauty has led to the most fundamental discoveries.

The analysis of complexity[edit]

To analyze a complex system is to identify its parts, to say how they are assembled and, if the system is dynamic, how they interact. Since a part is generally itself a system composed of parts, which are themselves systems, and so on, we distinguish several levels, the macro level, that is the level of the whole system, and various micro, or nano levels.

We often give ourselves as an ideal of knowledge an analysis such that the macro level be explained by the micro one. The system properties and its movement or behavior shall be explained from the properties of the parts, their movements or behaviors, how they are assembled and their laws of interaction. When this ideal of knowledge is reached, we have a reductionist, or analytic, explanation of the system. In empirical science, complex systems are often too poorly known for such an ideal to be achieved. However, when it comes to abstract beings, this ideal of analytic knowledge is always achieved, because abstract beings are completely determined by our definitions. Even if it is very complex, an abstract system always consists of very simple elements, whose fundamental properties are fully known. The principles that enable us to infer its properties from those of its parts and their assembly mode are also fully known and may be formulated with a few simple laws.

It is sometimes claimed that the ideal of analytical knowledge be rejected, because the micro level itself may have to be explained from the macro level. For example, to understand the behavior of an individual, one must know the society in which he or she lives. But this does not contradict the ideal of analytic knowledge. It asks that social phenomena be explained from individual behavior, but it does not require that we know everything about the individuals before knowing their society. In order to know the individuals, all sources of knowledge are welcome, including knowledge already gained on their society. There is indeed a circle, because we use the knowledge at the micro level to gain knowledge at the macro level and vice versa, but it is not vicious. We develop knowledge on complex systems by a dialogue between the macro and micro levels.

Reductionist explanations are sometimes ridiculed as reductionism, a kind of materialistic and scientistic program that would require all our scientific knowledge to be proven with reductionist explanations from the fundamental laws of interaction between elementary particles. Such a program is perfectly unrealistic since its implementation would reduce science to elementary particle physics, or to nothing, because particle physics can not be developed without the help of other sciences. Even the physics of atoms and molecules would not be a science because it requires auxiliary principles which are not proven from those of particle physics.

Reductionist explanations are widely used in all empirical sciences, but there is probably not one scientist who would approve the reductionist program as it has been formulated above. And except for physicists, they are few to worry about the interactions between particles and their laws, which in general they do not know.

The purpose of reductionist explanations, the ideal of analytic knowledge that they strive to achieve, is not to prove everything from particle physics. It is indeed to understand the real world and all that it contains as vast complex systems, which are all made from the same elements, and whose behaviors result from the interactions between these elements. But it does require that everything be proven from the laws of interaction between the elements. The purpose of a reductionist explanation is not even necessarily to prove. If the parts and their laws of interaction are already well known then yes reductionist explanations sometimes enable us to prove macroscopic laws from microscopic ones. But often we give a reductionist explanation by merely postulating microscopic laws. In such cases, the macroscopic laws resulting from microscopic laws are unproven. They are not less hypothetical than the premises from which they arise. Despite its hypothetical nature, such an explanation can still have great scientific value if it dispels some of the mystery of complexity.

As long as we do not know the composition of a complex system nor any analytic explanation of its behavior, it remains very mysterious, even if it is familiar. Sometimes we know from experiments laws that enable us to anticipate effects, reactions, results, but these laws themselves remain very mysterious. Even if we know how to justify them, by the correctness of the expectations to which they lead, or by proving them from other well justified observation laws, they do not lose their mystery. Only analytic explanations can dispel some of the mystery (but they often lead to other mysteries, since the microscopic laws themselves must be explained, unless it is assumed that the parts are elementary). As long as one does not have an analytic explanation of a law of behavior of a complex system, there is a lack of explanation. The ideal of analytic knowledge, to explain everything from their parts, is always adopted when we try to understand complex systems. If it is not satisfied, it asks to be satisfied. This ideal is a driving force for scientific discovery because we sometimes find the explanations we seek.

To give oneself an ideal of analytic knowledge for empirical sciences amounts to asserting that matter is intelligible, that the observable universe can be explained with theories, that our theories need only a few principles that determine the properties of parts or elements, assemblies, and their interaction laws, to explain the behavior of all complex systems we observe. It is not clear a priori that such an ideal can be really achieved. Why should matter be intelligible? This is doubtful. Nothing requires it to be so. Is not the universe far more than anything we can think of?

We give ourselves an ideal of intelligibility and sometimes of beauty as evaluation criteria simply by a voluntary choice. We want our theories, empirical, ethical, or abstract, to have simple and general principles. We want them to enable us to understand complex systems from their constituents. And we want them to be beautiful, as far as possible.

The knowledge of ends[edit]

An agent can explain his behavior simply by saying what he wants and the means he has gathered. Even if he does not explain it, we can understand his behavior by putting ourselves in his place, imagining that we want what he wants and believe what he believes. If we succeed in simulating internally the chain of actions, their motivations and the beliefs that accompany them, we can explain his behavior in the same way as himself (Weber 1904-1917).

The understanding of ends enables us to explain the behavior of humans and many animals. To explain what they do we only need to know what they want and the means they give themselves. Understanding ends is fundamental to preparation for action and learning, because we learn to act by understanding the purposes of others.

The understanding of ends enables us to explain also the functioning of an artificial system. We understand it when we understanding inventors or engineers who have imagined the ends, the functions, that the system can accomplish. Explanation by ends is equally fundamental for the science of the functioning of living bodies, physiology (Aristotle, Parts of animals). In this field, the validity of explanation by ends is a priori very surprising, because there is no engineer who has drawn the plans of living bodies. How can the organs of living beings have ends if there is no inventor who has imagined them?

The darwinian theory of evolution by natural selection suffices to dispel this mystery. Living forms are naturally selected by their ability to achieve their ends (growth, survival and reproduction). If their organs do not fulfill their functions, they do not leave descent. The accumulation of small variations in each generation and the selection of those that are the most functional are sufficient to explain the appearance of all these living forms, so sophisticated that they often go far beyond the understanding of engineers (Darwin 1859, Dawkins 1997).

The understanding of ends is of fundamental importance for ethical knowledge, since we learn to evaluate actions, behaviors and ends by knowing ourselves and others as agents who want and who give themselves ways.

Evaluation of ethical knowledge[edit]

An ethical knowledge is used to evaluate actions. But it must itself be evaluated. We do not want any evaluation system. We want a good ethical knowledge. Should we then design an infinite succession of ethical knowledge, the first evaluates the actions, the second evaluates the first, and so on?

The adoption of an ethical knowledge, the approval or disapproval of ethical principles are themselves actions. In approving an ethical principle we act on ourselves because we determine our will. It is indeed an action because we change reality. We are different before and after the approval of a principle.

An ethical knowledge is general. It is used to evaluate all actions (or sometimes all of a certain category). An ethical knowledge can therefore be used to evaluate ethical knowledge. There is no infinite regress of ethical knowledge because the same knowledge is used in the evaluation of all actions, including the approval of ethical principles. In fact, whatever wisdom we adopt, that we should honor it is always a principle of wisdom. An ethical knowledge always evaluates itself positively. When we adopt an ethical principle we are not only committed to honor all the actions that the principle explicitly asks us to honor, we are also committed to honor the principle itself and its adoption.

Some ethical principles explicitly provide evaluation criteria for ethical principles. For example, «You will recognize them by their fruits» is an ethical principle which is used to evaluate ethical principles, it can even be used to evaluate itself: it is a good principle because it produces fruits every time it enables us to recognize a good principle. Of course such evidence can not convince a skeptic who doubts the principle. But it shows that the evaluation of principles does not lead to an infinite regress.

We use our ethical knowledge to evaluate all other ethical knowledge. The more an ethical knowledge is consistent with ours, the more we honor it. The more it contradicts us and the more we despise or hate it. When we adopt an ethical knowledge we automatically find ourselves in disagreement with those who have chosen an ethical knowledge that contradicts us. As disagreements often escalate into violent conflicts, the diversity of ethical knowledge contributes to a perpetual war between humans.

Is there not a universal ethical knowledge on which all people could agree? A universal ethical truth? If such truth existed it would also be the true evaluation of ethical knowledge, since a bad ethical knowledge is poorly evaluated when it evaluates itself. But many ethical knowledge developed by human beings usually claim to be precisely this universal truth, and they often contradict each other. This leads to doubt the possibility of such a truth. It could be just a dream, a kinf of mind wandering. Some evidence suggests, however, that we must doubt this doubt.

An ethical knowledge is a part of a know-how-to-live (the sum of all the skills that enable one to live). Its value depends on the life in which it is integrated. If for example such an ethical knowledge directs us towards unattainable goals, because we do not have the appropriate skills, it is automatically disqualified because it does not help us to live well, because it tends rather to prevent us from living well.

We often conceive ethics or morality as a system of prohibitions which tends to limit the scope of our actions, to reduce the space of possibilities. But quite the opposite is true. Teaching us what is desirable, ethical knowledge makes us see opportunities that we would not have thought of otherwise. And giving us rules for action, it increases our capabilities, because there are many goals that require discipline to be achieved.

An ethical knowledge is always subject to the test of life. It proves itself, it shows its value in helping us to live well and making us discover good ways of living. Thus we experience the truth of the ideal. Dreams are among the paths to the truth, because they make us discover what does not yet exist. The truth of dream is not nonsense.

An ethical knowledge is evaluated from the behaviors it evaluates. There is indeed a circle, but it is not vicious. An ethical knowledge develops naturally so, by a kind of dialogue between ideal and experience.

All human beings naturally have the same basic needs (Maslow 1954): nutrition, protection against the weather, health, safety, integration in a community that respects us and recognizes us, to love oneself, love others and be loved by them, to accomplish oneself ... An ethical knowledge that collides with the satisfaction of these needs is automatically disqualified because they are necessary to live well. Basic needs thus determine an universal ethical knowledge, which can be recognized by all human beings. To assess this knowledge as a universal truth is simply to say that we really have these basic needs. Such knowledge is not enough to decide all ethical issues, but it is always a foundation from which we can reason.

An ethical knowledge can lead to self-destruction, if it makes us despise what we need to live. We then witness the sad spectacle of a will which annihilates itself, because of poor ethical knowledge. The will must want itself, it must want to continue to exist, it shall not want its own destruction. The spirit must be for the spirit (Hegel 1830). This principle is a universal ethical truth. It can not be reduced to a mere selfishness because our basic needs are often social needs. When we are united we want the will of others to continue to exist. To want the spirit is not only to want oneself selfishly, it is also and above all to want the society to remain a good place for the spirit to live.

A common misinterpretation of Darwin's theory says that natural selection necessarily imposes selfishness. Since they are in competition with each other, living beings would have to always promote their individual interests over those of others. The most important would be to have claws and teeth. But this interpretation ignores the pervasiveness of cooperation and solidarity in the living world. Like many animals we have solidarity instincts. Believing that selfishness is a law of nature is a grave mistake. Naturally, we need to stand together to accomplish ourselves.

Justification and evaluation of the knowledge about knowledge[edit]

The ways of knowledge recognition, justification and evaluation presented in this chapter, from the silent recognition of knowledge to the evaluation of ethics, are intended to recognize, justify and evaluate all forms of knowledge, silent and talking, from the most elementary perception to the most elaborate empirical, ethical, or abstract theories. The knowledge about knowledge, whether silent or talking, empirical, ethical or abstract, must be recognized, justified and evaluated in the same way as the others. Showing how the various forms of knowledge must be recognized, justified and evaluated, the knowledge about knowledge at the same time shows how it is self acknowledged, justified and evaluated.

Since the problems of knowledge justification and evaluation are ethical problems (what claims to knowledge should we honor?) the solutions presented in this chapter are themselves an ethical knowledge that should be recognized, justified and evaluated in the same way as any other ethical knowledge.

Just as an ideal of life shows us its truth in enabling us to live well, an ideal of knowledge shows us its truth in enabling us to acquire good knowledge. We know that our ideal of knowledge enables us to recognize and justify a good knowledge simply because it works very well, because it produces fruits, because with this ideal we give ourselves the means to acquire much good knowledge, while without it we remain more or less ignorant. In particular, the development of empirical science proves by the fact, in an unquestionable way, that the ideal of intelligibility can be achieved, and that simple principles in small number are sometimes enough to explain the behavior of the complex systems we observe. More generally all sciences, when they are well developed, justify a posteriori the ideal of knowledge that led to seek them.

An ideal of knowledge is evaluated from the knowledge that it enables us to recognize or discover. Like all ethical knowledge, the knowledge of the ideal of knowledge is developed by a sort of dialogue between ideal and experience.

Our ideal of knowledge is rationalist and humanist. It is defined by universal ethical truths. To respect all human beings as observers, we must honor good observations. To respect us as reasoners, we must honor the logical correctness of reasoning. To respect us as experimenters, we must honor well-controlled experiments and the empirical laws they verify. To respect us as theorists, we must honor the ideal of intelligibility. To respect us as workers, we must honor the efficiency of skills. Finally and above all, to respect us as rational human beings, we must honor humanist ethical knowledge.

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White needs Blue , Blue needs Green and Green needs White, to stand up.

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