About Philosophy in Relation to Common Sense—Mortimer Adler

MORTIMER J. ADLER, PH.D.

Are our minds cognitive–that is, are they instruments whereby we are able to acquire knowledge and attain understanding of the real world that is the same reality for all of us?

Is our experience of that reality sufficiently the same for all of us so that each of us can communicate about it with other human beings all over the globe?

Is there any need to prove the existence of an external world, one that has an independent reality, one that is the same whether we know it or not, and no matter how we know it?

Can a person who has learned to think in one language also learn to think in another of the many diverse human languages, and will the general tenor of that thinking be altered by the shift from one language to another?

Does the mentality of human beings differ with the diverse cultures in which we are reared and in which we live, or is the human mind basically the same throughout the world, differing only in superficial respects from one culture to another?

With the possible exception of the last question, persons of uninstructed–or should I say “unsophisticated”–common sense would without hesitation answer the first four questions with affirmations, unqualified by serious doubts. I say “uninstructed or unsophisticated common sense” in order to exclude those who have in one way or another been affected (I almost said “infected”) by major strains in modern philosophical thought.

Before I explain my stress on the word “modern,” I should, perhaps, apologize to my readers (all of whom I expect are persons of common sense) for bothering them with the perversities of modern thought, especially its many forms of idealism. My justification for doing so, however, is that they need to know the extent to which their fellowmen have been misled by academic philosophy in the nineteenth and twentieth centuries.

Returning for the moment to the question of acculturation, to which I made an exception, let me point out that we are all familiar with the commonsense opinion that there is an oriental mind that differs from the occidental mind, or even that the minds of African tribesmen or Australian aborigines are not the same as the minds of European city folk. But this commonsense opinion is not so strong that it cannot be easily made subject to doubt and even to retraction.

With regard to the questions we have been considering, commonsense persons concur in thinking:

  • 1. that the human mind is the same the whole world over, not only in all times and places but also in spite of the diversity of languages and cultures;
  • 2. that there exists a reality that is independent of our minds;
  • 3. that we have minds which enable us to know and understand that reality which, being independent of our minds, is the same for all of us and;
  • 4. that our human experience of that independent reality has enough in common for all of us that we are able to talk intelligibly about it to one another.

In these four statements, the stress is on the sameness of the human mind everywhere, on the sameness of the reality that is independent of our minds and the object of its knowledge, and on what is common or the same in our experience of it. I will try to defend the central point made in these four statements.

Defend it against whom? The answer is: the most eminent figures in modern philosophy and many prominent professors of philosophy, psychology, linguistics, and cultural anthropology in our contemporary universities. In doing so, I will be defending common sense against the philosophical mistakes, perplexities, subtleties, and puzzlements that have arisen in philosophical thought since the end of the seventeenth century and are widely prevalent today.

The conflict between philosophy and common sense is almost entirely modern. Under the educational institutions of antiquity and the Middle Ages, the great mass of commonsense individuals in the populations were not instructed by the philosophy that then exisited; today, however, with going to college or university routine for so many, and with current philosophical books available to so many, the situation is otherwise.

The commonsense minds of many are corrupted and turned against themselves by philosophical doctrines that urge them to renounce their common sense.

I have in a recently published book (Ten Philosophical Mistakes, 1985) dealt at length with the philosophical mistakes that are mainly modern. Here I wish to comment only on the modern philosophical tendencies that are so subversive of common sense.

Readers would probably be surprised and puzzled to have me say that idealism is a peculiarly modern philosophical malady–puzzled by my use of that word and surprised that there is little or no trace of it in antiquity or in the Middle Ages.

The puzzlement comes from a misunderstanding of the word itself. Most people use the word “idealism” to refer to the motivation of those who aspire to go beyond the way things are to the way things ought to be. In this sense, realists are those who acquiesce in the way things are. Idealists are those who wish to improve on them and make them better.

That is not, however, the way I use the word “idealism” or its antonym “realism.” My use has nothing at all to do with political, economic, or social reforms or with the betterment of any of our institutions. In that sense, Plato was certainly an idealist in his portrayal of the ideal state in the Republic. And even though Plato affirmed the independent existence of ideas as the intelligible objects of the intellect, he was, in that affirmation, a realist because he was asserting the real existence of the ideas–a reality independent of intellects and the same for all of us.

When I say that idealism is a peculiarly modern philosophical malady, I have in mind a number of theses that have appeared for the first time in modern thought.

They are:

  • 1. the denial that there is an independent reality, which is the object of our knowledge and understanding, or at least the denial of a reality that is the same for all of us;
  • 2. the assertion that the structure and features of the world in which we live and the shape of our experience of it are determined by the ideas we employ to think about it;
  • 3. the assertion that the innate structure of our minds–our senses, our imagination, and our intellect–is itself constitutive of the world we experience;
  • 4. the belief that the experienced world is not the same as an unknowable independent reality if that unknowable, independent reality does in fact exist;
  • 5. the view that there is a variety among our experienced worlds, varying with the ideas that diverse persons employ in thinking about them;
  • 6. the doctrine that our own ideas are only the objects with which we can have direct acquaintance, though they can also somehow be regarded as representations of a reality with which we cannot have direct acquaintance or of which we cannot have experience.

In all of these briefly summarized theses, except the first, the word “idea” is the crucial operative word; hence, the justification of the epithet “idealism” to describe those who endorse or espouse one or more of those positions. In the first statement, the word “idea” does not occur, but a knowable, independent reality is denied, which amounts to saying that the only objects of our knowledge must either be our own ideas or an experienced world whose structure and features are determined by our ideas.

There is something strangely remarkable about the fact that the idealistic trend in philosophy is predominantly if not exclusively modern and conspicuously absent in antiquity and Middle Ages. The extent of the scientific knowledge that has come into our possession since the seventeenth century is incomparably greater than what was known in all earlier centuries. Yet in the centuries in which it is generally recognized that knowledge has exploded and increased many times over, the philosophers have advanced and embraced doctrines that deny the existence of a reality that can be known, or they deny that its structure and features are independent of the minds that claim to know reality.

It almost seems as if the more knowledge we claim to have, knowledge that commonsense individuals acquire and apply, the less philosophers are prepared to accept it as genuine knowledge and that the more puzzled they have become about the nature and validity of knowledge.

In earlier chapters I have discussed the materialist strain in modern thought, which resulted in the denial of an intellectual power distinct from and superior to the senses that are embodied in physical organs. Materialism, beginning with Thomas Hobbes, is one of the two main strains in modern thought. The other is idealism, subjective idealism as in Bishop Berkeley or objective idealism as in Immanuel Kant. These two strains are often intermingled, though they may also exist in separation from one another.

These two errors are contrary to one another, which means that both can be false. They involve two fundamental mistakes about the human mind.

One is that our own ideas are that which we know, not that whereby we know. The other is denial of the intellect as a cognitive power quite distinct from the cognitive power of our senses, sensitive memory, and imagination. Only in antiquity and in the Middle Ages are there philosophers who are both realists and, with regard to the intellect, also immaterialists.

The metaphysical materialism that I criticized in the chapters of Part I is opposed to the idealism with which we are going to be concerned in Part II. That idealism denies the existence of an independent reality, material or immaterial. When materialists deny the existence of an immaterial intellect, their doing so derives from their primary dogma: that nothing except bodies or material things really exist. The materialists never question (in fact, they assume or dogmatically assert) that brains really do exist and so do machines.

For the materialists, metaphysics is the first philosophy, but for the idealists it is psychology, especially cognitive psychology. And their interest in that subject is usually limited to epistemology, or the theory of knowledge. We must remember that knowledge may consist of probable truths or truths that have certitude, truths that are beyond the shadow of a doubt.

The Greek word epistémé, which gives us the root of “epistemology,” signifies the latter kind of knowledge, consisting of truths that can be affirmed with certitude. If the search for certainty had been entirely abandoned in modern times, epistemology would never have come into existence. Its prominence, almost its centrality in modern philosophical thought, begins with the German philosopher Immanuel Kant. Whereas for Aristotle metaphysics was the part of speculative philosophy that dealt with the most ultimate questions, for Kant and his followers epistemology replaced metaphysics.

How did this happen? Kant tells us that he was awakened from his dogmatic slumbers as metaphysician by reading the philosophical works of the Scotsman David Hume. What had Hume done to agitate Kant’s mind? Influenced by the mistaken views of his predecessors, Locke and Berkeley, who asserted that ideas were the objects of our experience and that we had immediate acquaintance only with our own ideas, Hume challenged the prevalent acceptance of Newtonian mechanics as knowledge that had certitude.

Horrified by this, Kant developed a theory of the human mind that attributed to it an innate structure that in turn enabled it to determine the structure and features of all possible experience. Kant’s theory managed to give the laws of Newtonian mechanics the requisite certitude in the world we experience.

As I have observed elsewhere, Kant could have achieved the same result with much less philosophical effort and ingenuity by simply correcting the errors in Hume’s psychology, especially the errors in his philosophy of mind–his denial of the intellect and of abstract ideas, denials that led to a self-refuting nominalism.

The picture of the mind–the senses and the understanding or intellect–that Kant concocted had no corresponding reality. It should have been completely discarded once mathematical and experimental physics overturned Newtonian mechanics as no longer a comprehensive account of the physical universe, and as soon as the non-Euclidean geometries replaced Euclid as applicable to the spherical space of the globe.

That, unfortunately, did not happen. The seeds of Kantian idealism continued to germinate in modern thought and produced philosophical doctrines more and more at variance with the commonsense views that most of us hold, live by, and act on. From the commonsense point of view, some of these post-Kantian doctrines are almost unintelligible in their perversity. Whereas in antiquity and the Middle Ages philosophers merely deepened and extended, by their refinements and reflections, the views of reality and of the experienced world held by men of common sense, philosophers in the last two centuries part company with common sense and move away from it in a diametrically opposed direction.

I said a moment ago that the idealistic tendencies of modern thought are, to put it mildly, at variance with the commonsense views that most of us live by and act on. When philosophers are puzzled by what commonsense persons claim to know and that they act on such knowledge, that philosophical puzzlement in no way alters what is known. All sorts of perplexities arise in philosophical attempts to explain how we know something and how we assess the validity of our claim to know or the probability of our knowledge. But these perplexities and puzzlements, even if they are so profound as to be irresolvable, do not invalidate our claim to know something or alter our assessment of the probability of that knowledge.

It is a peculiarly modern error to suppose that because we cannot give a completely acceptable account of how we know something, we therefore do not in fact know it. The twentieth-century philosopher Ludwig Wittgenstein said that philosophy is doing the work it should do when it unties the knots in our understanding, when it overcomes the difficulties encountered in explaining how we know something. But, in my view, most of those knots and difficulties result from the errors of philosophers who tied the knots in the first place. Hence, it seems to me that it would be better to correct the original errors rather than work at untying the knots that resulted from those errors.

For example, commonsense persons have no doubt whatsoever that other human beings have minds so much like their own that no insuperable obstacles to communication are encountered. It may be difficult to give an adequate analytical account of how we know this, since the minds of other persons are not directly observable to us, and reasons must be given to validate the inference to the conclusion that others do in fact really have minds like our own. But however extensive and subtle that philosophical account may become, our commonsense inference from observable evidence available to us remains sound and supports the conclusion we act on without doubt.

Nor do commonsense persons need the prodding of philosophers to acknowledge that reality is not always what it appears to be. In jewelry stores all of us have questioned whether the gem being displayed is a real pearl or an imitation, a real diamond or a fake. When we say “it looks like a diamond, but . . .” we are making a distinction between appearance and reality. That commonsense distinction may require philosophical refinement in order to assess the difference between reality in itself and quite apart from us, and reality as we experience it. But philosophy goes astray when in modern times its idealist tendency leads it to deny that reality in itself and apart from us exists and is knowable, or to deny that our experience of reality gives rise to knowledge about it.

To deny a reality independent of our mind is to deny that anything ever existed before man came on this earth. Yet our paleontologists and our zoologists tell us what that reality was like before man existed. To say that reality before mankind existed is unknowable is to deny all our scientific knowledge of the prehuman world.

All of this is so preposterous and perverse that it will be hard for commonsense readers to take it seriously. Nevertheless, those readers must be told and must believe that there is hardly any doctrine so weird and crackpot that philosophers, especially modern philosophers, have not seriously espoused it.


This essay is from Chapter 7 of “INTELLECT: Mind Over Matter” by Mortimer J. Adler (Macmillan Publishing Company, 1990)


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Mortimer Jerome Adler (1902 – 2001) was an American philosopher, educator, and popular author. As a philosopher he worked within the Aristotelian and Thomistic traditions. He worked for Columbia University, the University of Chicago, Encyclopædia Britannica, and Adler’s own Institute for Philosophical Research. Adler went on to found the Great Books of the Western World program and the Great Books Foundation. He founded and served as director of the Institute for Philosophical Research. He also served on the Board of Editors of Encyclopædia Britannica from its inception and became its chairmen. Spearheading the fifteenth edition of Britannica he was instrumental in the major reorganization of knowledge embodied in that edition. He founded the Paideia Program, a grade-school curriculum centered around guided reading and discussion of difficult works (as judged for each grade). With Max Weismann, he founded the Center for the Study of The Great Ideas. He also served along with Max Weisman on the Board of Directors of Jonathan Dolhenty’s Radical Academy.