English 233: Introduction to Western Humanities  — Baroque and Enlightenment"

Immanuel Kant's "What Is Enlightenment?"
A Brief Introduction

Kant's place in the history of Western philosophy

The immensely influential German philosopher Immanuel Kant (1724-1804) spent his entire life in Koenigsberg, in the northern part of East Prussia, and is now known as Kaliningrad, in Russia. 

His mature work, which began to appear in 1781, is considered the culmination of early modern philosophy.  So decisive was his "Copernican revolution in philosophy" (as he liked to call his central critical "move"), that almost all subsequent work in philosophy can be described as "post-Kantian" in some important respect or another. 

When Kant came upon the scene, modern European philosophy was divided into two camps.  The predominant current in Britain was empiricist:  the main figures were Bacon, Locke, Berkeley, and Hume.  The ruling trend on the Continent was rationalist:  the central figures were Descartes, Spinoza, and Leibniz.  Rationalists insisted that to count as knowledge, belief ought to be certain, and that certainty can be achieved only through reasoning by valid inferential steps from undoubtable axioms -- principles whose denial led to contradiction or which were simply self-evident upon inspection.  These ideas, and reason itself, they believed to be inborn in every member of the species -- "innate."  Empiricists argued that the existence of innate ideas was an illusion, and that knowledge is acquired only through experience, and (ultimately) through the senses.  Such knowledge, however, could in principle never be certain, but was always subject to correction in the light of further experience. 

Kant took up the conflicting claims of the empirical and rationalist traditions and found a way that he believed managed both to account for their respective inadequacies and yet to incorporate important aspects of each.  The way he did so, however, was radically re-orienting.  He boldly turned a deep-seated traditional assumption on its head.  And the result was that certain concerns traditionally at the center of philosophical debate were ruled out as intrinsically hopeless from the standpoint of knowledge, and no longer worth pursuing. 

Both modernist currents -- as well as the traditional scholasticism and ancient authorities they undertook to displace -- were concerned to discover how our knowledge might correspond to external objects (however variously these objects of knowledge were conceived).  Kant's originality was to suggest that this "common sense" way of thinking of the relations of subject and object, of mind and world, might be "the wrong way round."  Copernicus had proposed that our conviction that the sun circles the earth might be mistaken, and that various difficulties that had theretofore proved intractable within the framework of that assumption might be made to disappear if astronomers were to invert it, and explore what could be explained if the earth were understood to circle the sun.  Kant proposed that we invert the assumption that our knowledge conforms to the nature of objects, and explore the assumption that objects conform to our ways of knowing

These ways of knowing, according to Kant, were of two kinds, inasmuch as objects appear to us under the double aspect of sensible and intelligible things.  In sensation, objects disclose themselves to us through the "forms of sensibility" -- i.e., modes characteristic of our consciousness -- that we call space and time.  That is, Kant argues, space and time are not to be thought of as objective properties of the world independent of human consciousness, but as the way in which objects are apprehended by human consciousness.   And insofar as objects are "thought," i.e., capable of being reasoned about, they must, whatever they may be in themselves, submit to certain pure relational concepts of the mind (Kant calls these "categories").  Among these, crucially for science (as for everyday practical affairs), is the idea of causality, according to which nothing happens that is not the result of antecedent conditions sufficient to bring it about.  In other words, it is an insistence of the rational constitution of human beings -- and not necessarily of objects "in themselves" -- that happenings be neither "self-caused" nor "uncaused."  Equally crucial for science (and everyday life), are basic quantitative notions (e.g., unity and multiplicity), without which we could not calculate certain consequences of spatial and temporal relations.

You can think of Kant's Critique of Pure Reason (1781) as a radical extension of ideas you are already familiar with.  Recall the arguments Galileo used to wedge a distinction between "secondary" and "primary" qualities, and from this distinction think back to Bacon's class of "Idols of the Tribe."  It might at first glance seem that Protagoras, who held that "man is the measure of all things," is closer to the Kantian position than Bacon, who denies this.  But if the way Protagoras' maxim has been construed in the course of history is correct, then he meant that the human mind can be relied upon as putting us in contact with objective properties of things in the world.  Bacon's point was that "the human mind is like a false mirror that distorts and discolors what it reflects, mixing its own nature with that of the world."  

Note that this very figure of speech makes it clear that, ironically, Bacon was thinking of color per se as an objective quality of objects, or at least of the light streaming from them into the eye.  (He's saying only that our perceptual apparatus works changes [he does not specify what sort!] in a way that is analogous to the manner in which a defective mirror transmits an image altered in colors and shapes from what was received by the mirror at its outside surface.)  However, as 17th-century thinkers went on to insist, the idea that objects "in nature" (i.e., imagined as independent of human sensory apprehension of them, or "in themselves") are possessed of color properties is an illusion.  And, indeed, since then modern physics has developed a quite impressive theory of light that gives a specific picture of how this is supposed to be:  color phenomena are that into which, in our experience, the physical constitution of the human species (lens, retina, optic nerves, visual cortex) converts (a certain limited range of) electromagnetic energy selectively reflected from various surfaces.  That is, "in color" is how we, in virtue of our particular shared perceptual equipment, experience a world that color predicates -- "red," "yellow," "green," etc. -- simply do not apply to.  Light waves are hypothesized to have quite definite, and mathematically formulable properties -- wave shapes, with lengths, frequencies, and amplitudes.  Of the particular combination of electromagnetic energies falling upon them, different surfaces (your shirt, a leaf) selectively absorb only the energy arriving in specific frequency ranges, and turn back the rest.  Their properties are not "blue," "green," etc., but whatever structural or electronic features that determine which combinations of light energy of particular frequencies it absorbs, and which it reflects to your eye that your sensory equipment in turn "translates" into the experience of "blue," "green," etc.

Similarly, as Galileo was able to argue even in the 17th Century, the thermal sensation we have of hot and cold objects is no more a property of those objects themselves than the tickling sensation we have when stroked by a feature is a property "in" the feather (as if the feather were experiencing tickling constantly, and only imparts this to us, by allowing it to flow into us, when we get stroked by it).  Galileo hazarded the guess that different states of heat in objects must be different rates of motion of the tiny particles that make up the (cruder) entities we call objects.  (Some two centuries after Galileo, this approach was developed into the modern theory of thermodynamics by the French engineer Nicolas-Léonard Sadi Carnot, the German physicist Rudolf Clausius, and the British physicist Lord Kelvin.)

Galileo's conviction, however, was that "the Book of Nature is written in mathematics."  That is, while he saw clearly that such qualities as smells, tastes, colors, heat and cold (as those terms were exclusively used in his day, i.e., as descriptions of sensations) were properties of the perceiving subject rather than of the world of objects that gave rise to them when mediated by our species constitution, Galileo believed that other directly perceivable qualities -- such as shape, weight, relative motion (and ratios among these such as densities, speeds, rates of vibration -- were real properties of objects that vision, touch, and calculation (a form of reasoning) can lay hold of.  Galileo regards these latter as causally prior to the others, which exist only in us, as a result of the working of these real qualities upon our sensory apparatus.  Hence the jargon of "primary" and "secondary" qualities.

But in reviving Pythagoras' conviction that "the language of nature is number," he was stopping short of Kant, who argues that space and time themselves are "modes of sensibility," rather than properties of the objective world, and, moreover, that it is our mind's prior structuring by the categories (of causality and quantitative relationships) to which space and time yield a world of objects susceptible to being rationally understood.  The world, whatever it is in itself, discloses itself to us only through experiences we have that exhibit temporal and spatial aspects.  But what we experience is what our nature converts whatever is out there into, for us, and can never be taken to be an aspect of "things in themselves."

Only insofar as the world appears to us through these modes (space & time, plus the categories of thought, like causation and number) can it be known, says Kant.  But these modes are characteristic of us as subjects, not objective properties of the world of objects in themselves.

The work of Kant's last 2 decades is notoriously difficult reading, however, and is not in its details a part of the story that it is the central business of our course to develop.  That is why in our course we are not going to take up a selection from one of his philosophical treatises, but will confine ourselves to a famous essay he wrote for a newspaper directed at the non-specialist reading public.  Before proceeding to that, though, we need to note a couple of additional points. 

One is that one of the results of his approach was to show that certain central problems of traditional "metaphysics" were in principle incapable of being solved.  In particular:  although Kant believed that he had explained how knowledge of nature and of certain basic moral universals is possible, his way of doing so had the consequence that certain questions (Kant called them "transcendental" questions) -- concerning the immortality of the soul, the existence of God, and the freedom of the will -- cannot, in their very nature, ever be resolved by appeal to any possible experience.  But this means that answers pro or con concerning them can necessarily never aspire to being knowledge.  Now that in turn means that certain basic elements of the Judeo Christian religious outlook are relegated strictly to faith -- and in a way that makes "faith" indistinguishable from logically just "begging the question."  Put another way:  faith in this sense invites itself to be seen as intrinsically irrational, so that it is impossible to give an account of it that divorces it from mere (conscious or unconscious) feelings.  But if faith itself is basically an expression of wishes, desire, and fears, it finds itself embarrassed within the context of the very religious tradition which had elevated it (as both Catholicism and Protestantism do) as an essential factor in salvation.  For within that same religious tradition, passions, desires and fears (and self-regarding wishes in general) are held in suspicion, as expressions of concupiscence.

As already mentioned, Kant did not confine his attention solely to philosophy of science and metaphysics.  He also set out, in his Critique of Practical Reason and in his Fundamentals of the Metaphysic of Morals to examine whether ethics -- like science, but unlike metaphysics -- can be shown to rest upon a rational foundation.  Kant's answer was a resounding "Yes."  He maintained that practical reason -- the dictates of our rational faculties when applied to questions of action, that is, of decisions, or acts of will -- was capable of determining what the morally right course of action would consist in, in a given situation.  He used the term "categorical imperative" to refer to obligations that are binding upon rational agents in any situation whatever.  (He distinguishes categorical imperatives from hypothetical imperatives, which are rules or maxims that govern our conduct if we adopt certain ends -- for example, if we decide to seek to maximize profit in a business enterprise, or if we want to live as long as possible, or if we want to be loyal to the king.  Imperatives that are binding "categorically," in contrast, are binding period.)  One formulation he gives the categorical imperative is:  act only on that maxim that you can consistently will to be acted upon universally -- that is, by all agents in all circumstances.  An example of a maxim that is ruled out by this formula is the principle that we should keep our promises when it is in our interests to do so, but should break them whenever doing so would be to our advantage.  Kant points out how the categorical imperative applies to this principle as a candidate for being recognized as a moral principle:  if everyone were always to break his promises whenever it suited him to do so, promises would no longer be a feature of social life because, since no one would believe them, no one would bother to give them.  It is, he says, logically impossible for one to will that everyone break promises when it suits since one could not do so if there were no promises in the first place.

This is not the place to go into the criticisms that have been lodged against Kant's claims on behalf of categorical imperatives, of the formulations he offers of them, and of the examples he puts forward to illustrate their import.  Instead we need to note what Kant was seeking to do -- what the nature of his project was.  It was a project that would make no sense to St. Augustine, to Thomas Aquinas, to Luther, to Calvin, or to a pope.  For Kant's aim was to show how the natural constitution of man as such -- and specifically, human reasoning. which determines what is and is not consistent -- was competent to settle all ethical questions, completely without reference to the will of any divine being.  The criterion he appealed to for doing this was that any ethical principle be universal, that is, that it apply equally to everyone.  In the moral sphere there are no special privileges for "nobles." 

Kant was thus thoroughly in sympathy with the aims of the French Revolution, which enunciated the famous Declaration of the Rights of Man and of the Citizen -- declaring the equality of all before the law on the basis of natural rights.  The basis of the legitimacy of this, in Kant's view, is that Reason (considered as a capacity, though not necessarily as an active skill) is the possession of all human beings by nature (i.e., in virtue of their being born with the constitution characteristic of the species).  For it is by Reason that we can agree, Kant holds, that a maxim like the one about breaking promises when convenient cannot be consistently be willed to be universal.  And it is this shared human competence that makes unnecessary any appeal to the Will of God, and hence appeals to Holy Scripture, or to a divinely appointed human authority, or to one's own private (merely individual) communications with God (as in the case of mystics and prophets).  Such appeals themselves, in any case, inevitably beg the question at issue, and this because they require commitments on "metaphysical" issues that are intrinsically incapable of being solved by rational means.  For Kant, this means not that they rely on something nobler and more authoritative than human reason (that is what Luther's claim that "faith is God's work in man" amounts to), but that they have entered the seas of irrationality.  To do this is to open the door to being arbitrary and capricious, and in the end to be able to prevail only by resort to violence when confronted with other people who do not accept (say) the divinity of Jesus, or the prophet-hood of Mohammed.

Keep in mind, then, where Kant believes his following his own reason leads, together with his conviction that reason (considered as a capacity, though not necessarily as an actively realized skill) is a faculty shared among all non-impaired human beings, by nature.  If you do this, you'll be able to appreciate in a deeper way what he understood to be at stake in the position he put before the general reading public in his essay, "What Is Enlightenment?"  This he published in 1784 in a Berlin newspaper.  While much of his major work still lay in the future, his Critique of Pure Reason had already appeared, and his reputation in Europe was made. The Revolution in France, too, was still to come.  (The Bastille would fall in 1789, and Louis XVI would go to the guillotine in 1792.)  But the assumptions shared by many of its major actors are clear to be seen -- even on the other side of Europe.

  Go directly to the Immanuel Kant's "What Is Enlightenment?"    Or:  read further first.

The opening paragraph of "What Is Enlightenment?":
Sample translations (and the original German)

Translation by Lewis White Beck, from Immanuel Kant, On History, ed., with an introduction, by Lewis White Beck (Indianapolis: Bobbs-Merrill, 1963), p. 3:

Enlightenment is man's release from his self-incurred tutelage. Tutelage is man's inability to make use of his understanding without direction from another. Self-incurred is this tutelage when its cause lies not in lack of reason but in lack of resolution and courage to use it without direction from another. Sapere aude! "Have courage to use your own reason!" — that is the motto of enlightenment.

Translation by A.F.M. Willich, from Immanuel Kant, Essays and Treatises on Moral, Political and Various Philosophical Subjects (London, 1798, 1799); reprinted in Frank E. Manuel, ed., The Enlightenment (Englewood Cliffs, NJ: Prentice-Hall, 1965), p. 35.

Enlightening is, Man's quitting the nonage° occasioned by himself. Nonage or minority is the inability of making use of one's own understanding without the guidance of another. This nonage is occasioned by one's self, when the cause of it is not from want of understanding, but of resolution and courage to use one's own understanding without the guidance of another. Sapere aude! Have courage to make use of thy own understanding! is therefore the dictum of enlightening.
 ° Nonage:  the condition of "not [being] of age."

Translation by Peter Gay, from Introduction to Contemporary Civilization in the West, 2 vols., 2nd Ed. (1954), I, 1071; reprinted in Gay, The Enlightenment: A Comprehensive Anthology (New York: Simon and Schuster, 1973), p. 384.

Enlightenment is man's emergence from his self-imposed nonage.  Nonage is the inability to use one's own understanding without another's guidance. This nonage is self-imposed if its cause lies not in lack of understanding but in indecision and lack of courage to use one's own mind without another's guidance. Dare to know! (Sapere aude.) "Have the courage to use your own understanding," is therefore the motto of the enlightenment.

 A bit more breezy, but still to the point, might be something like this:

Enlightenment is getting out of the childhood that you've kept yourself in.  Mentally, you're still a minor if you can't use your mind without having someone else tell you what and how to think.  This is your own fault if the problem is not that you have the bad luck to be retarded or brain-damaged, but that you just can't make up your own mind, and are afraid to use your brains without someone else dictating what you think.  Sapere aude! Dare to know!  "Have the guts to use your own wits," is thus the slogan of the Enlightenment.

And now, for those eager for German, here’s the original as Kant wrote it:

Aufklärung ist der Ausgang des Menschen aus seiner selbst verschuldeten Unmündigkeit.°  Unmündigkeit is das Unvermögen, sich seines Verstandes ohne Leitung eines anderen zu bedienen. Selbstverschuldet ist diese Unmündigkeit, wenn die Ursache derselben nicht am Mangel des Verstandes, sondern der Entschließung and des Muthes liegt, sich seiner ohne Leitung eines andern zu bedienen. Sapere aude! Habe Muth dich deines eigenen Verstandes zu bedienen! is also der Wahlspruch der Aufklärung. 

° unmündig:   This German term covers two conditions that in English and American law are distinguished as "non compos mentis" (a Latin term applied to adults who cannot manage their own affairs, because they "don’t have mastery of their minds") and "minority" in the sense of "not being of age."  It comes from the word Mund ("mouth"), and thus literally means "not being able to speak for oneself.  Correspondingly, the term for "legal guardian" is Vormünder — "one who speaks for another."

Some points of reference:

c. 19-18 BC.

The Roman poet Horace, writing during the reign of the Emperor Augustus, composes the Epistles to the Pisos, also known subsequently as the Ars Poetica (the Art of Poetry), three verse letters consisting of almost 30 maxims for the guidance of young poets. One of these is Sapere aude! ("Dare to know!")


First performance of the third and final version of Tartuffe, at the Palais-Royal, before King Louis XIV. A head-of-household (Orgon) chooses a religious guru (Tartuffe) to regulate the conduct of himself and his family, eventually committing all his personal affairs into the hands of this guardian of virtue, with nearly disastrous results, since Tartuffe is a conniving hypocrite.


An important circle in the German Enlightenment, The Society of the Friends of Truth, adopts as its motto Horace's maxim Sapere aude!


First appearance of Voltaire's Candide. Recall this passage, which begins with the Venetian senator Pococurante's summing up for his visitors his views of the authors whose works comprise his library.

"Fools admire everything in an author of reputation. For my part, I read only to please myself. I like only that which serves my purpose."

    Candide, having been educated never to judge for himself, was much surprised at what he heard. Martin found there was a good deal of reason in Pococurante's remarks. 


First edition of Voltaire's Philosophical Dictionary, including the article entitled "Freedom of Thought," in the form of a dialogue between the Englishman Lord Boldmind and the Portuguese Count Medroso (whose name means "fearful," "timorous," "frightened," "afraid").


Voltaire publishes Dialogues between A, B, and C. The Eighth and Ninth Conversations concern, respectively, "Bodily Serfs" and "Spiritual Serfs." (Esprit in French means both "sprit" and "intellect.")


Kant publishes "What Is Enlightenment?" in the Berlinischer Monatscrift, a Berlin monthly directed to the general public.


The English poet William Blake calls attention to the phenomenon of "mind-forged manacles" in his poem "London." 


The German poet Bertolt Brecht addresses a few words to his countrymen who, put up with the uncertainties of the Weimar Republic and the Great Depression, looked with hope at the ascension to power of Adolph Hitler:  "I hear you don't want to learn anything."

Sometime in the 1970s.

Kansas State University decides to comply with the ruling of the United States Supreme Court that public universities do not stand in loco parentis (in the place of parents) with respect to students who attend them, and therefore have no business unilaterally regulating their private conduct.

  Go to Voltaire's dialogue on "Freedom of Thought" from the Philosophical Dictionary.

  Go to Immanuel Kant's "What Is Enlightenment?"

  Suggestions are welcome.  Please send your comments to lyman@ksu.edu .

      Contents copyright © 1997 by Lyman A. Baker.  Thanks go to Wolf Roder for pointing out some errors in an earlier draft.

Permission is granted for non-commercial educational use; all other rights reserved.

  This page last updated 11 October 2000.