What is Philosophy?

Busts of Sokrates, Antisthenes, Chrysippos, Epikouros / Photo by Matt Neale, Wikimedia Commons

By Dr. Peter O’Hara / 05.29.1997


Philosophy has two main meanings, of an attitude to life, and of a type of knowledge. This lecture is concerned largely with the second meaning, that is, a type of knowledge. However the attitude or way of living has a relationship with the knowledge version of philosophy. Philosophy has been driven, from its beginning in Greece about 500 BC, by the desire for knowledge more certain than ordinary knowledge. Ordinary knowledge has its limits and is open to doubts and uncertainties. People have striven after certainty.

Philosophers have been those who have wondered about what constitutes really reliable knowledge: whether from our senses, or from mathematics and logic, or from some other source or combination of the above. They have asked whether knowledge based on reflection can give new knowledge about the world outside us. To illustrate this, consider a triangle. You can draw triangles and measure their angles and see that the 3 angles add up to 180°. But you can also prove, without using any measurements, that the 3 angles of any triangle add up to 180°. You may ask whether the geometric proof, which is a logical form of knowledge, has told you something about the real world.

Some philosophers have speculated about whether there is a real world outside us, or is all sensation of such a world purely due to our minds. Some have debated whether examining the world can tell us what ethics or morals to adopt. Philosophers have wondered does the world have a purpose, and can philosophical debate decide if humans have a purpose. Some have thought about whether natural observations can tell us about a supernatural world. Different philosophers have given different answers to these questions.

Many philosophies have been elaborate systems, based on some few principles, and from these deriving or deducing views on ethics, politics, art, religion, and science. They have varied on how much philosophy can say about these subjects.

The different answers involve several schools of thought in philosophy. Some are named after their originator and others named descriptively. I propose to describe changes in the model of what is philosophy, touching on some of these schools.

Much work in philosophy has been about solving these problems. But a lot of philosophers’ work has been about showing where past solutions were mistaken, or where the idea of the problem was itself misguided. So a lot of philosophy has been and still is a reaction to or a disagreement with previous philosophical work.

Philosophy has at times started with common sense. Often the doubt about existing knowledge involves doubting the common sense view of a subject. Philosophy’s conclusions have often disagreed with common sense.

I intend to talk about what is the subject- matter of philosophy, about what methods it can use, and about what conclusions have been reached (this last on only a very limited part of philosophy). Going through these matters we will talk about a view, and then look at the advantages and disadvantages of that view, and see what other views have been put up in their stead.

Why people incline towards Philosophy

Map of Athens, 5th century BCE / Missouri State University, Creative Commons

I have said that philosophy began in Greece about 500 BCE with a quest for more certain knowledge. People were aware that various things they might think they knew were doubtful or false. As an example, consider a simple object such as a table, and one of its qualities such as its colour. You will notice many colours on its different parts, varying as the angle of light on that part, so it is hard to decide on a definite one colour. In dull or in sunny light the appearance will differ. Proceeding on form this, some philosophers have decided that our single colour which we say is the colour of the table- brown, let us say- exists in our mind and does not exist so strongly in the real world. A few philosophers have proceeded further and decided that matter is less real than mind and mental events. This leads on to more far reaching questions, such as what are things or the world made of, whether there is a mind or spirit in charge of the world, and whether the world has any purpose.

Few philosophers have claimed that finding answers to these questions is easy, and the answers given have varied much. As we will see, many philosophers have been most moved by how they felt previous solutions have been false or unsatisfactory.

The Subject Matter of Philosophy

Thus the original and perhaps still commonest view of philosophy’s subject matter is of a type of knowledge. One version of this is seen as about questions that cannot be answered by science, yet are worth asking, and can be elucidated or partly answered by reason and debate.

Another set of philosophers have a model of philosophy covering quite a wider territory, seeing it as a grand- or super-science.

This definition looks quite broad. There can be problems where it is taken as too broad. Philosophy is Greek for love of wisdom, and it originally included natural philosophy, which is what is now called science. In Greece from 500 BCE many people wrote both about science (natural philosophy) and about the other subjects which can not be answered by examining nature. This tradition has continued to some extent. Although most scientists do not get involved in philosophy, many philosophers take an interest in some sciences. Although physics has kept its distinction from philosophy since Isaac Newton, psychology was still not free of the philosophers a hundred years ago. Today, the problem of the relation between mind and body, or now, between mind and brain, remains a philosophical problem, but the philosophers, the psychologists, and the neuroscientists have worked out a reasonable relationship between their areas of knowledge.

This broad idea of philosophy as a king of sciences is present in some ancient and some mediaeval philosophy. As examples I would give Plato, Aristotle, and Thomas Aquinas. Thomism (following Thomas Aquinas) persists into the present century. In this century the most noted Neo-Thomist has been Jacques Maritain (1882-1973). This was a reasonable position while natural science was undeveloped, and some knowledge obtained purely by reason and debate was clearly more reliable than any scientific knowledge. But philosophy was reluctant to give up this territory, and criticisms of the universal science model were made.

Reason as the source of the most reliable knowledge

One of the oldest surviving fragments of Euclid’s Elements, found at Oxyrhynchusand dated to circa AD 100 (P. Oxy. 29). The diagram accompanies Book II, Proposition 5. / Wikimedia Commons

I should explain a bit here about how knowledge obtained by reason and argument alone has been seen as more reliable than knowledge from the senses. It was not easy to settle whether the earth is round or flat- this is often debated today, even if few people decide it is flat. There have been other questions, such as what are the elementary substances of which the earth is made, and what the sun and moon are made of and how far away they are. It has taken centuries of science to answer these questions. In ancient and mediaeval times there were no definite answers.

By contrast, ancient mathematicians had shown, from a few axioms and using a limited number of rules of inference, that the sum of the 3 angles of a triangle was 2 right angles. This was proved without examining any real triangles; yet on examining real triangles the result is confirmed, in every case. This appeared to show that the most reliable knowledge is obtained by reason, and that it is knowledge about the external world.

One of the original questions for philosophy was what is the ultimate or basic substance the world is made of. This is now a question of physics. In spite of this being one of the more obvious faults of the king- of- sciences model, I believe it was not the source of the major criticisms of the model, which is to be expected as few physicists have also been philosophers.

Nevertheless several important lines of philosophers have sought to limit philosophy to those questions that are open to logic and argument, but do not involve anything that can be decided by experiment or examining the real world.

Why philosophy as King of Sciences was dethroned

Reason and argument were originally seen as the prime source of reliable knowledge. Plato referred to this as dialectic. In the 18th century Immanuel Kant, having been very impressed with how Isaac Newton described the real world by his theory of gravitation, wrote about how synthetic a priori propositions are possible. A priori means before examining any data; and synthetic means saying more than is merely implied by or contained in the starting premises. Kant viewed Newton’s theory as giving definite knowledge about the external world, in the same way as geometry had been thought to do from ancient times.

However, in the 18th and 19th centuries an inquiry into the elegance of Euclid’s geometry led to the dethronement of the position of pure thought as superior to examination of the real world.

Euclid’s geometry used a limited set of rules of inferences to derive theorems from already proven theorems. However he had to start from somewhere, so he took some “theorems” as for granted. These he called axioms or postulates. Euclid had 5 postulates. The first four are about points, lines, surfaces, and solid objects. The fifth postulate is quite different in character. The fifth postulate says that, in a plane, for any straight line and a point outside it, there is one and only one straight line in the plane that passes through the point but never meets the first line no matter how far it is extended in either direction. As this is called a parallel line the fifth postulate is also called the parallel postulate. For many centuries mathematicians were taken by the elegance of the first four postulates and the relative inelegance of the fifth postulate. In order to make geometry more elegant, attempts were made to try to prove the fifth postulate as a theorem from the first four postulates. These were not successful. In the 18th century Gerolamo Saccheri put forward two alternatives to Euclid’s fifth postulate, one being that no parallel line exists (every line through the point meets the first line), the other being that many or indeed infinitely many straight lines can be drawn through the outside point but not ever meeting the first line. He then showed that the consequences of either of these would be a geometry, so odd compared to the familiar geometry, that he thought this a proof of the fifth postulate by a reductio ad absurdum. However in the next century this was seen as the invention of two new geometries.

Accordingly by the start of this century it was seen as a matter of examination of the real world, or a matter of choice, whether to use the geometry of Euclid or one of the other geometries to describe, map, or model the external world. Euclidean geometry is just as useful as ever for most purposes. But in modelling the large universe there is debate as to whether non-Euclidean geometry is best. Another variety called Riemann geometry I understand is useful under Einstein’s theory of relativity in the vicinity of very massive objects.


Roman copy of a portrait bust by Silanion for the Academia in Athens (c.3

70 BC) / Capitoline Museums via Wikimedia Commons

As dialectic is said to be an older method than Russell’s logistic or analytic method, I will say a bit about it. Plato often refers to dialectic as his own method and as the highest form of knowledge. For Plato dialectic is the method of asking a question, giving an answer, and asking further questions until the matter is solved. Aristotle appears to have had the same meaning for dialectic.

The present day meaning of dialectic is different and is due to Georg Hegel, who was official philosopher to the Prussian kings in the early 19th century. Hegel saw that two opposing viewpoints may each contain some truth, and he said the dialectic method of reaching better knowledge is to seek a synthesis or a larger whole containing elements of both the opposing views. Hegel saw this as the main or the ideal method of getting greater wisdom or knowledge. Karl Marx took up Hegel’s version of dialectic and extended its use to his idea of the development of history and social structures.

I am here going to criticise Hegel’s dialectic, particularly when it is seen as the main or the ideal method for dealing with contradictory views. While in some or many cases the two (or more) opposing views may each contain an element of truth, there are other cases where the fault lies wholly or almost wholly in one of the opposed arguments. In the case of each particular argument, whether there be some truth in both sides, or one side is largely false, is open to examination in each case. If Hegel’s dialectic is applied to a case where truth is largely on one side of the argument, it leads us away from the truth. To extend this criticism to Karl Marx, there is no evidence to suggest that the development of social or political structures must proceed by an amalgamation or synthesis of the existing, competing, influences. As in the case of arguments, it is possible for one tendency to entirely obscure or triumph over the other influence(s).

In spite of the above, Hegel and Marx and their version of dialectic have many adherents still.

Philosophy as about mental contents or events

One of the most famous attempts to derive a system of certain knowledge was that of René Descartes, in 17th century France. Descartes exemplifies the method of logistic, that is of having simple elements of knowledge and deriving more complicated knowledge from them. He also illustrates the principle of abandoning all supposed present knowledge (because it is open to doubt) and trying to start from some small item that cannot be doubted. Descartes felt it was not open to doubt that he was thinking, and so he started his argument and his philosophy from there. From this he concluded that he definitely existed- cogito, ergo sum. Descartes founded the idea of rationalism, that if an idea is clearly formulated and clear in the mind, it is likely to be true.

From Descartes’ position of knowing he was thinking, it remains open to debate whether the outside world is real, or if it is merely the thoughts or dreams of the thinker. The idea of the world being one’s dream is called idealism. It sees matter as secondary to mind or spirit. The most celebrated idealist has been George Berkeley (18th century Ireland). He argued that physical things exist only while we or someone is watching or thinking about them; and the continuity of objects while no-one looks at or thinks of them is provided by God looking at or thinking of them. To most of us, the external world is taken for real because it is the simplest hypothesis; but if you look carefully at this hypothesis you will not be able to prove it is true.

The opposite to idealism is called realism (perceptual realism) – the idea that matter is primary to mind or spirit. Both idealism and perceptual realism talk a lot about mental events, and so to many philosophers, mental events constitute most or all of philosophy’s subject matter. Edmund Husserl (born in what is now the Czech republic in 1859) set the field of philosophy as being concerned with mental events, and called this view Phenomenology. Husserl’s aim was to make philosophy a strict science, and he saw the pre existing philosophy as borrowing methods and foundations from natural sciences. Undoubtedly he was right to withdraw philosophy from encroaching on physics and other sciences, but it is now clear that he instead borrowed the subject matter of psychology.

Philosophy as identical with logic, and analysis as its method

Bertrand Russell in 1938 / Wikimedia Commons

In moving against the super science model of philosophy, and limiting philosophy to a science of a priori propositions, not distinguishable from logic, Bertrand Russell in this century built on the realisation that geometry is logical and that we do not know a priori from geometry that the parallel postulate is true of the external world. But Russell was also moving against the tendency of many previous philosophers to construct a system from their thoughts and speculations. He thought that philosophers had from a limited starting point derived ideas about many varied fields such as politics, ethics, and theory of knowledge. He was concerned that they came to believe that, if the foundation of the system was good, all the ethical, political, or epistemological products would be good. He felt they were sometimes not so good, or at times very much mistaken. He substituted a piecemeal approach to reaching philosophical solutions, with two problems not necessarily using the same methods of solution.

Reactions to encroachment on science by greatly limiting the scope of philosophy

The discovery of non Euclidean geometries showed that logical argument was not as strong at proving things about the real world as had been thought for 2000 years. While physics became strong enough in its own right, from the time of Galileo and Newton, to separate from philosophy, psychological discussions continued in philosophy up to the start of this century. We have seen how Bertrand Russell sought to strip scientific matters, that is, those open to physical survey or experiment, from philosophy. At the turn of the last century psychology was beginning its independence. In ways psychology was the last object science still held within philosophy. For many centuries philosophers, from an armchair position, had commented or speculated on such matters that were open to experiment or examination. Partly because of this, the logical positivists, such as Rudolf Carnap and the Vienna Circle, said that philosophy should be limited to formulating the logical syntax of the sciences. This means setting out, by logic, what type of things it is reasonable, permissible, or logical to say. The logical positivists would say that any detail about the real world belongs to some “object science”, and philosophy has no business saying what any science should refer to.

Carnap and the logical positivists were also motivated by the competing schools of philosophy over the preceding few centuries, and with the impossibility of deciding between their competing views. One of the conclusions they reached was that many disagreements were because people have always used, and we still use, languages that are not logically exact: so that some disagreements are because the debaters are using the same words to refer to different things. The logical positivists therefore argued for a logically purer language, indeed several logically distinct languages. They required these languages to be in a hierarchy. Thus there would be an object language, in which we could talk about material objects such as tables and people. There would be at least one level of logical language above that, in which object-words are not used, but only logical ideas or propositions from the lower language would be referred to. They felt that many past philosophical problems had been combinations of object problems and logical problems, and that this was why the arguments had gone astray.

The logical positivists saw a place for science, object sciences as Carnap calls them. They also saw a place for logical argument about what types of proposition science could contain, and this was the subject matter of philosophy. This plan excluded many questions hitherto seen as part of philosophy, which the logical positivists considered to be pseudo-problems. These included ethical and theological questions. Russell shared the logical positivists’ call for several logically distinct types of language, but did not agree with their designation of so many questions as pseudo-problems.

Philosophy as inquiry without being tied to a particular method

Portrait of John Dewey / Library of Congress via Wikimedia Commons

John Dewey (USA 19th to 20th century) saw a problem with the aim of philosophy in finding more certain knowledge. Dewey saw that the philosophers recognised that the ordinary, common, knowledge was not reliable, and they were seeking to construct reliable knowledge on sound foundations. But he saw that what they hoped to end up proving as true was the existing knowledge. He thought that, instead of looking in an open minded manner to prove whatever would turn out at the end of the proofs, the philosophers typically hoped to prove to be true much of the existing beliefs. Dewey thought the existing beliefs came from emotional or tribal origins. He commented that philosophical discussions happen in a social context, and he felt that philosophical problems should be solved in a social context. He saw the aim of philosophy as clarifying problems. This is a valuable idea, attempting to save philosophy from interminable fruitless arguments, as have happened. However Dewey seems to withdraw philosophy from giving any rulings on the truth or relative truth of propositions.

Summary of the main philosophical problems

I think the most basic problem of philosophy has been about what type of knowledge is the most reliable, and how we obtain it. The main solutions that have been offered have been: that knowledge comes from pure thought or reason; that it is derived from sense data; that it comes from an interaction between an idea or theory and sense data. There have been several varieties of these views. There has been the idea that reason or thought can give knowledge of the external world, and the denial of this view.

To many people, the most important philosophical problem has been ethics or morals. I have not discussed the major views on ethics or morals as I feel it is quite a large subject and needs a lecture of its own. The solutions offered have included: that morals can be derived or read from nature, typically biology or human biology; that morals derive from some thing or being above nature (supernatural origin); that morals are entirely a matter of human choice. There have, again, been a few varieties among each of these.

Philosophy began with the problem of what is the nature of the world, or what it is composed of. Solutions have been- that it is composed of many things; or of one thing; matter being primary; or spirit being primary; a dualism of matter and mind, with a form of interaction between them.

Philosophy has also included logic, and has taken an interest in mathematics and its relationship to the external world. This includes the relationship of general or class words to words that refer to singular objects.

Present status of the main philosophical problems

The field in which pure reason, without any base in sense data, can give knowledge is now recognised as much smaller than was thought by the ancient philosophers. It does not give any knowledge about the external world, except about what is logically possible. The model of interaction between theory and sense data is the most widely supported source of knowledge.
In morals or ethics, I believe all of the solutions described above still have many adherents.

Many parts of the question on the nature of the world have been removed from philosophy and are now part of various sciences. The mind- body problem (mind- brain in some people’s version) has several competing solutions. Idealism has now quite few adherents.

The question of where the colour of an object resides, and how we perceive it, in spite of varied illumination of the object, has been taken out of philosophy and has a physiological solution.

Mathematics is now seen as a very extended and elaborate form of language, and not an aspect of the external world.

Philosophy has not answered the questions about purpose for the world or for humans. In this field the ability of philosophy to provide answers is seen as very much less than in ancient times.

In the general quest for certain knowledge, many criticisms of past philosophical solutions have moved us to see that the range of subjects on which certain knowledge can be obtained is a lot less than was thought or hoped for in antiquity.

Originally published by Minerva: An Online Open Access Journal of Philosophy (Volume 1, November 1997), an open access resource, for educational, non-commercial purposes.