Opinion

Plato's famous division of cognitive states appears most fully in the divided line of the Republic. The line has four segments: imagination, belief or opinion (pistis), mathematical understanding, and pure intellectual knowledge (noesis). The first two together constitute doxa (opinion), directed at the sensible world of particular things that come to be and pass away. The last two constitute episteme (knowledge), directed at the intelligible world of eternal forms. The key distinction is not between true and false claims but between the objects to which these cognitive states are directed: opinion attaches to particulars, knowledge to universals.

The Meno develops the distinction further with a famous image. Right opinion, Socrates says, is like Daedalus's statues: "beautiful enough, but they run away and escape if left untethered." The person who has right opinion about the road to Larissa can be just as useful as a guide as the person who knows the road. But her opinion is unstable; it may be overturned by a persuasive argument because she cannot "give an account" of why it is correct. Knowledge is tethered by reasoning; it can explain its own grounds. This is the pivotal distinction: the truth of opinion and knowledge may be the same, but their security and teachability differ radically.

In the Republic, Plato returns to the political consequences of the distinction. The philosophers who have ascended to knowledge of the Good are reluctant to return to the cave and govern. But they must, because only those who know the forms can make just laws and correct the confused opinions that the many take as their guide. The problem of democratic opinion is not that the many are necessarily wicked but that they are guided by appearance rather than reality, by the shadows on the cave wall rather than the light that casts them. Plato's political philosophy is ultimately an argument for epistemocracy: government by those who know.

Plato leaves the tradition a question that cuts into practical life as sharply as it cuts into epistemology: if knowledge requires tethering by rational account, and most people are incapable of that, does legitimate government require rule by an educated minority over the well-meaning but untethered many? Aristotle will resist this, insisting that received opinion is where philosophical inquiry must begin — not what it must overcome.

Aristotle accepts Plato's distinction between opinion and knowledge but gives it a different foundation. For Aristotle, science (episteme) deals with what is necessarily the case: propositions that could not be otherwise, demonstrated from first principles through valid inference. Opinion (doxa) deals with what is contingent: what is true, perhaps, most of the time or in most cases, but could be otherwise. This means that the physical world, subject to change and accident, falls largely within the domain of opinion except insofar as its general and necessary features can be demonstrated. Aristotle's classification of the sciences follows from this: physics is a science because it demonstrates necessary truths about natural change, but the particular facts of natural history are matters of experience and probable opinion.

What distinguishes Aristotle most sharply from Plato on this point is his respect for received opinions (endoxa). Where Plato treats common opinion as confusion that philosophy must overcome, Aristotle treats it as the starting point of dialectical inquiry. "We must examine the received opinions to see which of them are consistent and which inconsistent," he writes in the Nicomachean Ethics, and the examination proceeds by exposing tensions, making distinctions, and working toward a coherent position that preserves as much received wisdom as possible. This method treats ordinary human opinion not as ignorance to be swept away but as evidence of how things tend to appear to thoughtful people, evidence that any adequate theory must account for.

The practical consequences of Aristotle's position are significant. If opinion concerns the contingent, then practical wisdom (phronesis) deals fundamentally with opinion, not knowledge. The person of practical wisdom does not apply universal rules mechanically to cases; she perceives the particulars of the situation correctly and judges how to act well in conditions that are never fully predictable. This is why practical wisdom cannot be reduced to a science: it is the virtue of the person who forms correct opinions about contingent matters. Aristotle is thus the first thinker to give opinion a genuinely positive role in the ethical life, not as a deficient form of knowledge but as the proper cognitive mode for navigating a contingent world.

Aristotle's rehabilitation of opinion, and his insistence that dialectic must begin from received opinions, opens a space that Plato's epistemology closes off: the space of practical reason, rhetoric, and the political life, where certainty is unavailable and correct opinion is the best we can achieve.

Montaigne's Apology for Raymond Sebond is the most thoroughgoing assault on the idea of human knowledge in the early modern period. Montaigne does not merely argue that we often form mistaken opinions; he argues that the faculties by which we form all opinions are so unreliable that we cannot trust any of them with confidence. The senses deceive us regularly; reason is circular, resting on premises that themselves require justification; the judgments we make in one state of mind we revoke in another. "What I hold and believe today, I hold with my whole belief. Has it not befallen me, not only once but a thousand times, to have embraced some other thing with the same instruments, and in the same condition, which I have since judged to be false?"

Montaigne draws two distinct consequences from this skepticism. The first is intellectual humility: we should not hold our own opinions with dogmatic certainty, and we should not despise those who differ from us, since they are no more reliable judges than we are. The second consequence, more surprising, is social conservatism: since we cannot reason our way to better institutions, we should defer to custom and established practice rather than attempt to redesign society from first principles. The very uncertainty of opinion is, paradoxically, a reason for not acting on our opinions against the inherited order of things. Montaigne is skeptical of reformers and utopians not because he thinks the status quo is just, but because he thinks our judgments about what is better are no more reliable than our other opinions.

Religious faith occupies a special position in Montaigne's scheme. He exempts the articles of Christian faith from his general skepticism, not because he has evidence for them, but because faith is, by definition, a supernatural gift rather than a product of the natural faculties he has been criticizing. This exemption is formally consistent within his framework, but it also has the effect of placing the authority of the Church beyond the reach of the very skepticism Montaigne deploys against all other human claims. Whether this represents genuine piety, a sophisticated fideism, or a protective coloration for a fundamental unbelief remains disputed.

Montaigne is the source of modern skepticism about the possibility of knowledge in contingent matters. His Essays pass to Descartes, who responds to the challenge by seeking a firmer foundation; to Hume, who accepts the skeptical conclusion; and to the entire tradition of liberal tolerance, which finds in the uncertainty of opinion a reason for not coercing those who disagree.

Cervantes places at the center of his novel a pair of men whose opinions about the world they ride through are in constant disagreement, and whose disagreement the novel does not resolve by calling one of them right and the other wrong. Don Quixote, formed by his reading, holds the opinion that the field contains giants, that the barber's basin is the enchanted helmet of Mambrino, that a flock of sheep is an army advancing, that a peasant woman on a donkey is the lady Dulcinea under an enchantment. Sancho Panza, formed by the common experience of his village and by a well-developed sense of his own interest, holds the contrary opinions: that what his master sees are windmills, a basin, sheep, and a peasant woman. The question which runs through the novel is not how to decide between these two sets of opinions but how two men of good faith, looking at the same things, can arrive at views so completely at variance.

The older treatments of opinion, beginning with Plato's account of doxa as the state of mind that falls short of knowledge, had assumed that the correction of opinion was a matter of bringing the mind into closer contact with the object. Aristotle, more moderate on the point, had still assumed that opinion could be steadied by long experience and prudent judgment. Cervantes presents the more disturbing case in which long experience and prudent judgment already belong to Sancho, and closer contact with the object is already available to Don Quixote, and the gap remains. What separates the two men is not a lack of evidence but the prior conviction which each brings to the evidence. The knight's prior conviction is shaped by the books of chivalry, the squire's by the habits of village life, and each prior conviction is powerful enough to select from the available appearances the ones which confirm it.

The question this raises connects to the treatments of Memory and Imagination, where the knight's imagination is shown supplying his perceptions; to Knowledge, where the distinction between opinion and knowledge is considered; and to Truth, where the question is whether a single standard of truth is available for settling such disputes. What belongs to the idea of Opinion is the display of a case in which the formation of opinion is traced not to the object but to the observer, and in which the disagreement between two observers is found to be rooted in what each of them already brings with him to the act of observation.

Montaigne, in his essays on custom and on the force of imagination, had already observed how much of what men take for the testimony of their senses is in fact the testimony of their upbringing. Descartes, reading Cervantes or reading the world in which Cervantes wrote, will try to answer the problem by seeking a method for purifying opinion of its prior formations, a method so rigorous that only what remains after all opinion has been suspended can count as knowledge. Hume, moving in the opposite direction, will conclude that what we call our beliefs about the world are themselves habits of the mind, so that Sancho's confidence in the windmill and Don Quixote's confidence in the giant differ not in kind but only in the particular history which has produced them. The novel's questions survive all of these answers.

Descartes reads Montaigne as a challenge and responds with a method. If all the opinions received from parents, teachers, and tradition are potentially false, then the only way to find solid ground is to begin again: to doubt everything that can be doubted, and see what remains. The Meditations on First Philosophy performs this exercise. Descartes finds that he can doubt the existence of the external world, the reliability of his senses, and the truth of mathematics (a deceiving demon might be making him err even there). What he cannot doubt is that he is doubting. The thinking substance, in the very act of trying to deceive itself, proves its own existence: cogito ergo sum.

The cogito provides a standard for distinguishing knowledge from opinion. Clear and distinct perception produces certainty; whatever is not clear and distinct is mere opinion. The intellect, when it perceives clearly and distinctly, cannot be wrong, because God, who is not a deceiver, guarantees the reliability of our best cognitive faculties. The will errs when it outruns the intellect, assenting to what is not clearly perceived. Error, including the formation of false opinions, is thus a product of the will exercising its freedom beyond what the intellect clearly supports. This is Descartes's answer to the ancient question of how a good God can permit error: the fault is not in our nature but in our freedom.

Descartes thus reverses Montaigne's conclusion: the uncertainty of opinion is not a reason for deference to tradition, but an argument for the most radical skepticism as a preliminary to a rebuilt certainty. Once the cogito and the existence of God are established, the Cartesian project reconstructs science on secure foundations. But Descartes's critics, from Gassendi to Hume, will argue that the cogito proves less than it claims, and that the God whose existence Descartes proves is not available to guarantee the reliability of our faculties. The skeptical challenge that Descartes meant to answer has, in many philosophers' view, only been restated in a more pointed form.

Descartes attempts to escape opinion entirely by retreating to the pure self-evidence of the cogito. But the escape is unstable: his critics, from Gassendi onward, will argue that the clear and distinct ideas he trusts are themselves a kind of ratified opinion — and that the God he invokes to guarantee them is proved only by an argument that itself relies on the very cognitive faculties whose reliability is in question.

Locke's Essay Concerning Human Understanding is, among other things, a sustained reflection on the limits of human knowledge and the consequent necessity of acting on opinion in most areas of life. Knowledge, for Locke, consists in the mind's perception of the agreement or disagreement between its ideas. This perception, when direct and intuitive, produces the highest certainty; when demonstrated through a chain of intermediate ideas, it produces the certainty of demonstration; when it rests on the testimony of the senses about particular facts, it produces "sensitive knowledge." Beyond these three grades of knowledge lies the vast domain of probability and belief, which Locke calls "judgment."

Locke is notably more comfortable than either Plato or Descartes with the idea that most of human life must be conducted on the basis of opinion rather than knowledge. The probability of some opinions is so high that it "borders upon certainty" and we rightly treat it as if it were knowledge. The probability of others is low, and we should hold them tentatively. The test is not whether we have achieved Cartesian certainty, but whether we have weighed the evidence with appropriate care and proportioned our belief to the degree of probable evidence we have. "Whatever I embrace as truth, I would hold it with a degree of assent proportioned to the strength of those grounds."

Locke connects the inevitability of opinion in theology and ethics to his political argument for religious toleration. If even sincere and thoughtful people can form different opinions on matters of religion, then coercing conformity to any one set of religious opinions is both epistemically unjustifiable and politically illegitimate. The freedom to form and express religious opinions follows from the structure of opinion itself: opinion is not something one can be reasoned into or frightened out of by force; it responds only to evidence and argument. This epistemological argument for toleration runs through Locke's Letter Concerning Toleration and becomes one of the foundations of liberal political theory.

Locke naturalizes opinion by arguing that the vast domain of probability is not a regrettable limitation of the human mind but the appropriate domain for most of what matters in human life. The result is a more modest, tolerant, and practically useful epistemology than either Plato's or Descartes's.

Hume's radical conclusion about the limits of knowledge grows out of a deceptively simple distinction. "All the objects of human reason or enquiry may naturally be divided into two kinds, to wit, relations of ideas and matters of fact." Relations of ideas (mathematical and logical truths) are known by pure reason, without reference to experience; their denial would be self-contradictory. Matters of fact, including all claims about the real world and the causal connections within it, do not have this character: their denial is conceivable. No amount of reasoning alone can establish a matter of fact; all knowledge of matters of fact depends on experience. So far, this sounds like a stronger version of Locke's empiricism.

The radical step comes when Hume examines the foundation of our beliefs about matters of fact. Our beliefs about causal connection, on which all empirical science and practical life depend, are not grounded in reason or in direct observation of necessity. We observe constant conjunction: A is followed by B, regularly. But we never observe the necessary connection itself. What Hume discovers is that our expectation that A will be followed by B is a habit of the mind, not a perception of reality. Custom and imagination, not reason, generate our beliefs about the unobserved and the future. "Belief is more properly an act of the sensitive, than of the cogitative part of our natures."

The consequence is a thoroughgoing humility about opinion. Virtually all of our beliefs about the world, including the most fundamental principles of natural science, are matters of well-grounded habit and custom rather than of strict knowledge. Hume does not think this should make us doubt whether we will be burned if we put our hand in fire; these habits are reliable enough for practical purposes. But it should make us deeply skeptical of any philosophical or theological system that claims to have moved beyond probability to certain knowledge. The system-builders are not seeing farther than the rest of us; they are forming opinions with excessive confidence.

Hume's skeptical conclusions about knowledge and opinion disturbed Kant enough to "interrupt his dogmatic slumber." By reducing causal knowledge to habit-generated belief, Hume raises the question that will drive the next century of philosophy: if the best we can achieve is well-grounded opinion, what standard separates good opinion from bad?

Kant responds to Hume by accepting that our knowledge of the empirical world is conditioned by the forms of intuition and the categories of understanding, but insisting that this conditioning is precisely what makes empirical knowledge possible. Within the domain of possible experience, we can achieve genuine knowledge, not merely probable opinion. Beyond that domain, in the realm of metaphysics, theology, and pure rational cosmology, Kant agrees that we cannot achieve knowledge; but he disagrees that the result is mere custom-generated belief. Instead, he introduces a tripartite distinction among modes of holding something true.

Kant distinguishes Meinen (opinion), Glauben (belief), and Wissen (knowledge). Opinion is "the assent which, subjectively and objectively, is insufficient." Belief is "assent which is subjectively sufficient but objectively insufficient"; this is the appropriate attitude toward propositions we cannot know theoretically but must commit to for practical reasons. Knowledge is "assent which is both subjectively and objectively sufficient." This taxonomy is more refined than Locke's and more systematic than Hume's. Kant uses it to explain why the existence of God, freedom, and immortality, which cannot be demonstrated by theoretical reason, can nonetheless be affirmed with genuine conviction as the postulates of practical reason.

The practical postulates are Kant's most important contribution to the theory of opinion. He argues that reason demands, in the domain of morality, certain commitments that cannot be grounded in theoretical knowledge: we must act as if we are free, we must act as if God guarantees the correspondence of happiness and virtue in the long run. These are not dogmatic opinions about what can be known; they are rational commitments grounded in the requirements of the moral life. The resulting "moral faith" is something between Hume's habitual belief and the theological knowledge that dogmatic metaphysics claimed to possess.

Kant's tripartite scheme solves the Humean problem by assigning different cognitive statuses to different domains — but it leaves a tension that William James will exploit: if moral and religious claims can be legitimately held as rational beliefs without theoretical proof, why should we not extend this "sufficient subjective" assent wherever the stakes are high enough and the evidence is inconclusive?

William James inherits from Hume the insight that our beliefs are not strictly governed by evidence, and from Kant the recognition that commitment beyond theoretical knowledge is sometimes practically necessary. What he adds is a new criterion for evaluating beliefs: their consequences. Pragmatism holds that truth is not a static relation between ideas and reality but a process. "An idea is true so long as to believe it is profitable to our lives." This is not a license for wishful thinking; it means that the meaning of any belief lies in its practical consequences, and that we test beliefs by their fitness to guide us through experience.

James's famous essay "The Will to Believe" addresses the specific case where evidence is insufficient to determine belief but a decision cannot be avoided. He calls such situations "genuine options": they are live (both alternatives feel real), forced (no third alternative is available), and momentous (the stakes are high enough that abstaining from decision is itself a decision with consequences). In these cases, James argues, the will may legitimately influence belief. The person who withholds belief in God pending conclusive evidence has not avoided taking a risk; she has taken a different risk, one for which she is equally responsible. Agnosticism is not a neutral position; it is a commitment, with its own consequences.

James's psychology of belief, developed in The Principles of Psychology, connects the philosophical account to the natural history of the mind. Beliefs are habits: they dispose us to act in certain ways, to attend to certain features of our environment, and to assimilate new experience within established patterns. The stability of belief is a biological asset; the revision of belief in response to new evidence is equally necessary. James is interested in the conditions under which people form, revise, and abandon beliefs, and in the question of when holding a belief against the evidence is pathological and when it is simply a form of faith that the evidence does not yet support but may eventually vindicate.

James makes opinion into the central category of human cognitive life, not a deficient form of knowledge but the form in which most knowledge presents itself to beings who must act before certainty is available. The unresolved tension in his account is whether "what works" is a standard for truth or merely a description of how belief happens — a question Dewey will press by asking whether the whole distinction between opinion and knowledge should be replaced by a single standard of warranted assertion.