Opinion, Belief, Knowledge?

There is an empiricist commonplace that identifies “knowledge” with “justified true belief”. This makes knowledge an especially good kind of belief. I regard that as a flat-out category mistake.

I want to suggest that knowledge is not a kind of belief or opinion at all. As usual, I don’t claim to “know” what I “suggest” with some force as interesting or worthy of consideration, so in particular I do not claim to know that knowledge is not belief or opinion. (I am also not trying to say exactly what knowledge is, only to delimit it somewhat.)

What I am doing is recommending a different use of the word “knowledge”, that at minimum distinguishes it from belief or opinion. This is based on the belief or opinion that the belief or opinion that “knowledge is not belief or opinion” is a well-founded belief or opinion.

I read Plato as very sharply distinguishing “knowledge” properly so-called (epistémé) from any kind of doxa (opinion or belief). This would rule out the identification of knowledge with justified true belief.

It is not uncommon, however, to see claims that Plato himself identified knowledge with justified true belief. I will offer a different interpretation of the main relevant passage here. I apologize for using the old Jowett translation, which is easily accessible online.

“Then when the jurors are rightly persuaded of something one could not actually know except by being present — when they judge it, that is, on hearsay, and yet with a true opinion, they judge it without knowledge; even though, if their decision is sound, their persuasion is correct” (Plato, Theaetetus 201).

Ignoring the particular criterion of knowledge mentioned in the example, the essential is that on reflection, we should all be able to agree that there are cases in which we would say that someone has a true opinion without knowledge. So far, this is agnostic to whether or not knowledge is justified true opinion. It just establishes that true opinion in itself is not knowledge.

“When therefore anyone conceives a true opinion of anything without a reasoned statement, his mind is free from error about it, but does not know it; for the man who cannot give and accept a reasoned statement about anything, has not knowledge of it: but when he adds to his true opinion a reasoned statement, he has in addition all that is required to constitute knowledge” (202).

Here it is very important to distinguish between statements about knowledge and statements about someone who has it. What is argued in the above quotation is that the person who has a true opinion and a reasoned statement has what she needs for knowledge.

I would agree that a person who has knowledge can reasonably be said also to believe what she knows. But it does not follow from this that knowledge itself is any kind of belief, or in particular that knowledge is just true belief accompanied by a reasoned statement. Nothing in the argument excludes the possibility that knowledge itself — as distinct from the person who has both knowledge and belief — is tied only to the reasoned statement, and is in itself independent of the person’s belief.

I think this is already sufficient to disprove the claim that this section of the Theaetetus expresses the view that knowledge is reducible to justified true belief.

If knowledge were tied only to the reasoned statement, it would still be true that the person who also had a true belief would have what she needed for knowledge. Again, I don’t mean to say that “reasoned statement” is sufficient by itself to define knowledge, even though I think it gives an important hint. It is worth noting, however, that Plato’s mention of a reasoned statement is more specific than the simple mention of justification.

Also, “truth” is said in more than one way. The kind of truth that could reasonably be said of a belief or opinion is only a correspondence to facts. The kind of truth of principal interest to Plato was very different from this.

I also think there is a broad category of acquaintance that is extremely important to humans, but is different from knowledge. The kind of experience I find interesting is mainly not ephemeral immediate experience, but the more substantial thing that we mean when we say someone is “experienced”. (See also Imagination, Emotion, Opinion; Consciousness, Personhood; A Criterion for Knowledge?; Everyday Belief; Belief is Different from Faith.)

History of Ethics: Plato

Traditional communities, even the most “primitive” known to modern anthropology, have well-defined, generally accepted ways of distinguishing good and bad actions. Hegel called this “ethical substance”.

What I call “ethics” involves a second level, in which the criteria for good and bad are subject to discussion. Here we are not simply laying down the law, but inquiring into the principles that ought to govern distinctions between good and bad. The oldest documented example of this kind of inquiry in our planetary family of cultures is the writings of Plato. How much of the literary character of Socrates in Plato is attributable to the historic Socrates is debated by scholars, but need not concern us here. It is in Plato that we find an actual record of Socratic inquiry. Other so-called “minor Socratic” schools also claimed to be inspired by Socrates, but left no record of critical give and take comparable to what we find in the dialogues of Plato.

Plato clearly recognized the weakness of argument from authority, and put the reasoned examination of principles before the mere fact of anyone’s say-so. He further pointed out that assertions about God’s will and its applicability to real-world cases need to be evaluated as human assertions, on the same footing as others. In discussions about truth, there are no specially privileged assertions or asserters. He set a strong ideal of sincerely seeking knowledge rather than assuming we have it, and by example promoted the modest attitude that humans should avoid making strong claims that human knowledge cannot validate. Many of his most important ideas are only presented as what I call “suggestions”.

Provocatively, Plato suggested that all beings desire the good, and that the Good is the most ultimate formative principle of all things. This reduces evil to ignorance of the true Good. The tendentious claim here is that evil is a kind of lack or defect, and that no one who aims at what is really evil properly understands what they are doing. This gives fundamental ethical significance to knowledge and the quest for better understanding. Treating evil as due to some lack of understanding also suggests a way of forgiving the evil-doer.

For Plato, wisdom and goodness are correlative. Wisdom especially includes the recognition of what we do not know. It is superior to any law. The most wise are the best qualified to govern, but do not want the job and must be coaxed into doing it.

Plato was unconcerned with questions like who decides who is wise, preferring to focus instead on how such judgments should be made. For the latter, he suggested the same kind of free and open dialogue and examination of reasons as for any other questions about truth.

Imagination, Emotion, Opinion

In humans, the ethos associated with cultural, ethical, and spiritual life comes interwoven with what I have called “animal imagination”, tied to our organic being. The kind of imagination at issue here is not the modern, post-Romantic notion associated with artistic creativity, but part of the basic functioning of many animals. Aristotle associates it with what he calls the “common” sense, which again is not what we call common sense, but rather something fundamental to all perception, that also comes into play in the formation (what Kant would call synthesis) of perceptual wholes from the input of multiple senses. Aristotelian “imagination” involves activations of the common sense in the absence of inputs from external sense. It plays an essential role in memory and dreams. Like much in Aristotle, this is not really an explanatory theory, just an interpretive description of things we experience in ordinary life.

Aristotle is concerned to distinguish imagination from opinion, precisely because there is a close connection between the two. Much later, Spinoza essentially identified opinion with imagination. Aristotle emphasizes that opinion involves an additional element of belief that is not inherent to all imagination. He says there are animals that have imagination but no belief.

Opinion is closely related to Aristotelian practical judgment, although the latter classically refers to a deliberative process whose outcome is action rather than belief, whereas opinion is a kind of belief that is not knowledge. Opinion may be a result of past deliberation or reflection, but very often it is more or less spontaneous. I think Spinoza means to suggest that our less reflective opinions arise from a kind of imagination. Like practical judgment, imagination is concerned with particulars.

Spinoza especially brings out the connection of imagination with emotion. It seems to me these are strongly interdependent. Our emotions both shape our imaginings and are shaped by them. These are what mainly guide our initial responses to things, and we have this in common with other animals.

Even after we have more developed, reflective views of things, there is still an element of spontaneous imagination in any application of those views to new particulars.

Emotion is strongly connected with our apprehensions of value. Again, there are dependencies in both directions. Emotion is a source of many valuations, especially initial ones; but valuations also help shape emotion.

Being a rational animal is mainly a matter of potential. Degrees of actual reasonableness have to do mainly with our emotional constitution, not how much we know.

Three Kinds of Knowledge

Spinoza identifies three kinds of “knowledge”.

“From what has been said above, it is clear that we perceive many things and form universal notions:”

“I. from singular things which have been represented to us through the senses in a way that is mutilated, confused, and without order for the intellect…; for that reason I have been accustomed to call such perceptions knowledge from random experience;”

“II. from signs, e.g., from the fact that, having heard or read certain words, we recollect things, and form certain ideas of them, which are like them, and through which we imagine the things…. These two ways of regarding things I shall henceforth call knowledge of the first kind, opinion or imagination.”

“III. Finally, from the fact that we have common notions and adequate ideas of the properties of things…. This I shall call reason and the second kind of knowledge.”

“[IV.] In addition to these two kinds of knowledge, there is another, third kind, which we shall call intuitive knowledge. And this kind of knowing proceeds from an adequate idea of the formal essence of certain attributes of God to the adequate knowledge of the… essence of things” (Ethics, book 2, proposition 40, scholium 2, Collected Works vol. 1, Curley trans., pp. 477-478).

The first kind is the source of the confusion addressed in the last post. It elaborates on Plato’s account of “mere opinion”. An important detail is Spinoza’s explicit reference to the fact that inadequate “universal” notions are commonly formed based on inadequate ideas from perception and imagination. Formal logic can then be mechanically applied to these inadequate universals, yielding conclusions that are formally logically sound but deeply wrong materially or content-wise when applied to the real world. We’ve all seen this happen.

The second kind, which he calls “reason”, is thus distinguished not by its use of logic but by the kind of contents it addresses: common notions and adequate ideas. For Spinoza, “reasoning” that takes mere images and opinions as unproblematic sources of truth does not deserve the name of Reason.

“Common notions” is Spinoza’s preferred term for principles that are recognized by all humans and are “equally present in the part and the whole”. What exactly these are intended to include is somewhat obscure. His main example of common notions involves simple mathematical properties of bodies, which are “common” due to the presumed objectivity of mathematics, rather than any sort of intersubjectivity or mutual recognition.

“Adequacy” of ideas is an entirely internal criterion — basically a kind of coherence of meaning, rather than a correspondence with something external that is presumed to be independently known. Ideas for Spinoza are things we affirm or deny, so they have internal complexity. Adequacy of ideas seems to be entirely independent of his criteria for common notions, which is good because I worry about the narrowness of the latter.

I read the third kind — “intuition” — as presupposing and building on the discipline of the second. It is not a free-for-all. This is a “cumulative” rather than “originary” intuition. What other authors claim as originary intuition (alleged “self-evident truths” coming from nowhere) would for Spinoza be mere opinion or imagination.

He says that the first kind of knowledge is the only source of falsity, which implies that the results of the second and third kind are always true. While it is clear that the first kind is a source of falsity, to say that reason and “intuition” yield only truth sets a very high standard indeed. He does not seem to acknowledge the difficulty of knowing there is no admixture of the highly fallible first kind in what we may take to be the infallible second or third kind, or in general the difficulty of practically achieving the extremely high standards he sets for the second and third kind.

This whole discussion proceeds very hastily. There is a bit more than I have quoted, but only a bit. His account of the first kind of knowledge and its weaknesses is relatively more extended, and quite vivid and insightful. But the account of the second kind is very sketchy, and the account of the third kind even more so.

Perhaps we are intended to see the whole text of the Ethics as an illustration of how the second and third kind work. But if it purely embodies the infallible second and third kinds of knowledge, then it would seem that all serious philosophers ought to unequivocally endorse all its arguments, or else they won’t qualify as serious. Strictly speaking, does Spinoza’s standpoint even allow him to acknowledge another philosopher as serious who does not endorse all his arguments? Honestly I did not expect to write the previous sentence.

While Spinoza does not seem to me to be what Kant would call a dogmatist in the sense of taking objects for granted, there is a sense in which he does seem to say, “here is my system, take it or leave it”. I’m still not sure what I think of Hegel’s claim that no finite presentation can ever be truly final, but relatively speaking I’m more comfortable with that. I want to say it is actually a principle of charitable reading to at least in some measure tolerate excessive claims a work may make on its own behalf, and focus instead on understanding the content.


The popular adage “everyone has the right to their opinion” is a partial truth. It gestures at something like Kantian autonomy. But the other side of the coin is that Kantian autonomy does not operate in a vacuum; it is always embedded in what Wilfrid Sellars called the space of reasons, where holding a commitment is implicitly to invite questions about the reasons for it, and then about the actual validity or applicability of those reasons. As ethical beings we are responsible for our opinions.

An attitude in the ordinary unqualified sense may operate as a cause of behavior in the modern sense, but because nothing prevents such an attitude from being completely arbitrary, a mere attitude cannot serve as a justification for anything. Attitudes in this sense have a sort of vain Cartesian irrefutability, in the same way that mere appearances do. There is a level at which if you say something appears to you thus-and-such, that mere appearance is incontestable. But it is incontestable precisely because nothing follows from it.

Brandom, on the other hand, is only interested in attitudes from which something is taken to follow. When he talks about the attitude-dependence of norms, I think what he really has in mind is more specifically a dependence on what analytic philosophers call propositional attitudes. This additional specification is crucial. An endorsement of any proposition whatsoever can still qualify as a propositional attitude, but every proposition has a “place” in the space of reasons that situates it in a multi-dimensional spectrum of goodness of justification. Criteria for goodness of justification can of course be debated too, but this still means that the justification for any propositional attitude is subject to evaluation. We may judge a propositional attitude to be poorly founded and therefore wrong, but it still cannot be completely arbitrary, because its justification can be evaluated.

I don’t think the same can be said for the Enlightenment authors Brandom cites as promoting a dependence of norms on attitudes, like Pufendorf and Rousseau (see Modernity, Voluntarism; Modernity, Rouseau?). Their legal and political voluntarism explicitly purports to trump any evaluation in terms of the space of reasons. This is in spite of the fact that those authors were already departing from the most traditional notion of ethical norms as simply somehow pre-given. Precisely because I am deeply sympathetic to Brandom’s critique of the unilateral authority-obedience model, I disapprove of these authors’ appeals to sovereignty.

Brandom shares his mentor Richard Rorty’s concern for democratic values, and suggests that normativity be considered as a historical development. But in spite of his concern for “semantic descent” to relate the higher-order, overtly philosophical concepts Kant and Hegel focused on to the level of ordinary empirical concepts used in daily life, he still treats ordinary concepts in a general way. Consequently, when he thinks about ordinary concepts, he still does so in a way analogous to that of Kant and Hegel. This is not a bad thing; I think he is by far the strongest at this high level. Fortunately, the weaker remarks about concrete historical antecedents for his views are peripheral to the main development of his thought.


Plato’s short dialogue Meno — concerned with virtue and knowledge — is among the most famous of what are referred to as his “Socratic” dialogues, which dwell on Socratic method, and on the character of Socrates as a kind of role model. Meno wants Socrates to provide an easy answer to how virtue is to be acquired. Socrates, ever distrustful of easy answers, shifts the discussion toward the more basic question of what virtue is. Meno first responds with examples, but Socrates points out that examples do not answer the “what is” question.

Meno eventually suggests that virtue is the desire of honorable things, combined with the power of attaining them. Socrates then points out that some people desire evil, and that a person may have power, yet still fail to properly recognize good as good and evil as evil. Meno complains that Socrates is always doubting himself and making others doubt, and says he feels bewitched.

Socrates introduces a poetic myth that learning is a kind of recollection of knowledge that we already had. He then walks a young boy through a simple geometrical construction. At the beginning, the boy seems to have no idea how to solve the problem. Then he thinks he does, but he is wrong. At a later point, he recognizes the mistake. Socrates points out that it is always better to know that we do not know, than to think that we know when we do not. But still later, after following the steps of the construction, it seems like the boy does understand how to find the solution, though he is never told. As Brandom might remind us, this shows the value of making what was implicit into something explicit.

Eventually, Socrates leads Meno to the conclusion that virtue is “either wholly or partly wisdom”. But then he introduces a further doubt, whether virtue can be reduced to knowledge. True opinion is said to be as good a guide to action as knowledge, and this is said to be how most good people function.

But then finally, true opinion is said not to be of very great value after all, because it is not “fastened by the tie of the cause”, and therefore tends to “run away” from us. That is to say, when we do not really know — i.e., cannot articulate — the why of a conclusion that is right in one context, it is easy to misapply it in a different context. (See also Dialogue; Platonic Truth; What and Why; Reasons.)