The Problems of Philosophy by Russell


Bertrand Russell (1872 – 1971), studied Mathematics at Cambridge where his interests turned to logic and philosophy. In his lifetime he published over seventy works and was honoured with the Nobel Prize for Literature in 1950 for his coauthorship with Whitehead of their book on modern logic Principia Mathematica.

Due to his outspoken political views opposing British involvement on World War I, in 1916 he was dismissed from his Cambridge lectureship and imprisoned. 

He published A History of Western Philosophy in 1945. He was critical of the Stalinist-Leninist regime in the Soviet Union, but his opposition to the U.S. invasion of Vietnam led to condemnation of his opinions as communistic.

Russell had studied at Cambridge under lecturers of British Idealist ideology, which centred reality in the mind, but he later opted to confide in more objective scientific knowledge and analytic philosophy.

Philosophically Russell evolved from extreme realism, where thought meant reality, to a theory of descriptions recognising that names contain hidden descriptions. In The Problems of Philosophy he moved towards an empirical view of reality through his study of the British empiricists, Hume and Berkeley. This work argued that knowledge comes from experience based on sense-data.

Later Russell would argue that matter was constructed out of sense-data through logic. He abandoned a book on the theory due to the criticism of his student, Wittgenstein. He then turned to understanding modern physics.


It is said that Russel's work, The Problems of Philosophy (1912), is a treatment of old problems with new logic. He offers an overview of previous schools of thought and the philosophical problems common to them: public and private experience, personal identity, self-consciousness and consciousness of other minds, relations of space and time, and knowledge. Russell himself is interested in distinguishing knowledge of particulars in contrast to knowledge of universals and discriminating between appearance and reality. The book is written in 15 chapters.

Chapter 1 - Appearance and Reality

Russell begins by eliciting basic assumptions through the practice of radical doubt. He uses a simple experiment walking round his table and observing that the colours change depending on his position. Colour is not simple, but is in a complex relationship with the observer's point of view. This is made more complex through different observers and he concludes that the 'real' colour of an object is not unique, but open to argument, depending on the observer. The same is true of the shape, texture, sensation of pressure and sound of the table as it depends on how closely we can observe it. He asserts that the sensations of touch, sound and sight, are not fixed by a reality, they are possibilities and dependent on the conditions of observation. He concludes that there is a distinction between appearance and reality and that we construct the real by inferring it from our sense-data:

"the real table, if there is one, is not immediately known to us at all, but must be an inference from what is immediately known."

We may doubt the existence of a real table but we can have confidence in our awareness of the sense-data of everyday experience.

The next problem Russell addresses is the relationship between the real table and our sense-data. This leads to the questions: does matter exist and what might its nature be? He considers the first query in relation to the idealist concepts of Bishop Berkeley (1685–1753), who thought that physical objects do not exist independently of our minds:

"if there are any things that exist independently of us they cannot be the immediate objects of our sensations." 

Here Russell analyses the word "matter" linguistically. Berkeley considers, in a platonic manner, that physical objects exist, but only in the mind of God. Another idealist in the platonic tradition, Leibniz (1646–1716), asserted that physical objects existed because they were observed by a collective mind, such as the universe. 

Russell believes that there is a real table but he disagrees with the idealists about its nature. He thinks our sense-data are signs that there is something in existence independent of us. This provokes 

 "sense-data whenever we are in a suitable relation to the real table." 

He concludes that we infer reality from the appearances we gather from our sense-data.

Chapter 2 - The Existence of Matter

Russell's quest here is to answer the question of the existence of matter (physical objects), or not. He insists that while we doubt matter itself, 

"...we are not doubting the sense-data, which made us think there was a table..."

The author's reference here is to Descartes who set out from the extreme sceptical basis of doubting everything. He resolved his doubts by concluding that he necessarily existed. Russell underlines Descartes' contribution to philosophy: subjectivity is the surest basis for thinking:

"Granted that we are certain of our own sense-data, have we any reason for regarding them as signs of the existence of something else, which we can call the physical object?" 

Russell proposes that it is more reasonable and simpler to assume that physical objects exist, rather than accept the idealists' hypotheses that everything is a dream or consists of ideas in the mind if God.

He concludes that knowledge must

"... be built up upon our instinctive beliefs, and if these are rejected, nothing is left."

The philosopher's task is thus to analyse and organise these beliefs, so that they do not enter into contradiction.

Chapter 3 : The Nature of Matter

Supposing, then, that matter exists independently of sense-data, what else can we know about it?

Modernity has turned to science for the answers to the specific nature of matter, but these are often not linked to our subjective experience. For instance the scientific theory of light as a wave is very distant from our visual sensations of light. To clarify this Russell offers the explanation that sense-data give information about relationships of distance (far or near), but not of distances themselves. They also apprise us of the order of events in time, but not of duration.

Chapter 4 : Idealism

Russell examines in detail the Idealist philosophers' arguments that all existence is in the mind. Though it clashes with commonsense, he also notes that commonsense itself offers no answers to the nature of objects.

He accepts that Berkeley's arguments have stood the test of time. However he rejects the jump they make from the premise that everything is ideas to the conclusion that everything is in the mind. This confusion disappears, he says, if we accept that many things supposedly in the mind are actually captured by the mind. 

He also criticises the Idealists' conflation of two meanings of "know": to know something through sense-data (knowledge of things) and to judge it to be true (knowledge of truths). He then sets himself to untangle these two sorts of knowledge.

Chapter 5 : Knowledge by Acquaintance and Knowledge by Description

He asserts that all knowledge, both of things and of truths is through acquaintance. This kind of knowing extends to both particulars (specific things) and universals (ideas such as blackness and sisterhood).

He further develops the scope of knowledge to include description, claiming that it is the only type of knowledge through which objects or others' minds can be known. An object is known through description when only one object answers to the definition. He finally asserts that knowledge by description can be reduced to knowledge by acquaintance:

"...every proposition which we can understand must be composed wholly of constituents with which we are acquainted."

Chapter 6 : On Induction

The author's next quest is to understand how we construct inferences from our limited knowledge by acquaintance (knowledge of sense-data, memory, and possibly the self). He finds the answer in induction: the justification of future expectations from past experience, such as the assumption that the sun will rise because, so far, this has happened every day.

However, he also adds that induction is based on a conviction, 

"a belief which experience can neither confirm nor confute."

Chapter 7 : On Our Knowledge of General Principles

The philosopher sets out more principles central to philosophical thinking, but unprovable through experience:

- the law of identity: "whatever is, is." 

- the law of contradiction: "nothing can both be and not be."

- the law of the excluded middle: "everything must either be or not be".

These principles arose through the competing philosophies of the empiricists, who held that all knowledge came from experience, and the rationalists, who maintained that some truths are known a priori. (The principles of pure mathematics and logic are a priori.)

A priori principles can be induced from concrete examples, such as general truths about triangles understood from one triangle. However, a priori knowledge does not arise from empirical examples but from deductions by applying principles.

Chapter 8 : How A Priori Knowledge Is Possible.

To answer this question Russell turns to Kant who observed that a priori knowledge was not completely analytic. Previous to Kant philosophy held that a priori knowledge was analytic. Kant noticed that synthetic knowledge (joining premises to come to a new conclusion) was also a priori. He also asked the question: how can general knowledge take place when all experiences are particular? He replied by construing a priori knowledge, not as describing experience, but as filtering it.

However, Russell finds this explanation unsatisfactory, because a priori judgments are assertions of unchanging, universal truths, and human nature (as part of the existing world) is prone to change. He now needs to understand universals.

Chapter 9 : The World of Universals

Russell suggests a definition of universals which encompasses abstractions like 'justice' and concrete ideas such as 'whiteness'.

It was Plato who first raised the relationship of Universals and Particulars by introducing the unchangeable Forms in which physical realities participate. Russell asserts:

"all truths involve universals, and all knowledge of truths involves acquaintance with universals."

The nature of universals is shared among particulars: many physical objects are white; many individual actions are just. In grammar universals are represented as parts of speech, particulars are indicated by nouns and pronouns. This means that most sentences include universal references.

Historically, according to Russell, philosophers have often neglected the great variety of universals, frequently ignoring the type of universal known as a relation. They mistakenly fell into monism, which only recognises the universe as a unity, or they asserted that none of the separate entities of the universe could interact: monadism. Others, like the empiricists, equated universals with abstract ideas and negated their existence.

The author uses the concept of north to show that universals are neither solely physical nor mental. He says that Edinburgh is north of London, whether the traveller knows this, or not. However the expression "north of" does not exist in a place or time. 

To distinguish between particular objects and minds he suggests that physical objects have existence and universals have subsistence. Existence is in time; subsistence is timeless.

Chapter 10 : On Our Knowledge of Universals

Russell asserts that knowledge of both universals and particulars can be known by acquaintance or description or neither of these. He also considers that a priori knowledge deals only with the relations of universals and supports this with the example: "2 + 2 = 4", since this is a general statement, not an empirical generalisation like "all men are mortal."

He ends the chapter summarising the sources and types of knowledge discussed: 

- knowledge of things vs. knowledge of truths, 

- knowledge by acquaintance vs. by description, 

- intuitive vs. derivative knowledge.

Chapter 11 : On Intuitive Knowledge

Russell argues that on the analysis of beliefs there comes a point where the belief is self-evident. He accepts this as a basic, logical axiom. Knowledge derived from sense-data can also be taken to be self-evident: for example this object is to the right of that object; that shape is round. However, as memory is fallible there are degrees of self-evidence, with the highest quality being the most vivid and recent. 

Chapter 12 : Truth and Falsehood

The author considers, not the proofs but the meaning we give to the terms truth and falsehood. He offers three criteria for a theory of truth:

1) inclusion of the idea of falsehood, 

2) recognition that truth and falsehood are properties of beliefs, 

3) acknowledgement that the truth or falsehood of a belief has a basis in the external world.

Russell rejects the idea:

"that truth consists in... correspondence between belief and fact."

Or that truth consists in coherence, protesting that belief systems may be coherent, yet false, like the well elaborated narrative of a novelist. (Today the prime example of this is ChatGPT which has a very coherent discourse but may offer false datos, a phenomenon called 'hallucination'.)

The author proposes a theory where a belief is true if there is a corresponding fact. 

Chapter 13: Knowledge, Error, and Probable Opinion

Basing himself on the belief/fact correspondence, Russell queries the notion of knowing something is true. 

He asserts that knowledge is constituted by a belief inferred from premises known because they rest on intuitive knowledge. This does not depend on logic but may simply be based on another belief. 

He then distinguishes between infallible knowledge by acquaintance (direct perception of a fact) and fallible knowledge by judgment (from factual information), which is more opinion than knowledge. 

He adds that the more collective a belief is the more probable it is to be certain:

"a body of individually probable opinions, if they are mutually coherent, become more probable than any one of them would be individually." 

(Reality is the hallucinations shared by a cultural group.)

Chapter 14 : The Limits of Philosophical Knowledge

The author admits that his discussions have sidestepped several traditional topics of philosophy: God, the existence of good and evil, and the reality or irreality of matter.

He turns to Hegel as an example of a philosopher who applied logic to achieve knowledge of the universe. He describes Hegel's main thesis as holding that any separate piece of the universe is incomplete. To solve this shortcoming Hegel proposed a synthesis: an incomplete idea is combined with its antithesis. The repetition of this process makes the ideas more complete, closer to reality. In the end an absolute idea leads to an absolute reality.

Russell criticises Hegel's premise that we can know the fragmentariness of things enough to assert that. He suggests that the hegelian approach is a trend in modern philosophy to pinpoint seeming contradictions and apply reason to them. He considers that this apparent fragmentation is an illusion. 

However, he recognises that mathematical logic is a useful tool for exploring truth. He suggests that philosophy best serves as a means of critiquing knowledge. Despite not contributing much knowledge, philosophy "diminishes the risk of error" in human thinking.

Chapter 15 : The Value of Philosophy

Russell offers some thoughts on the value of philosophy. 

It poses more questions than answers, which frees thinkers from their prejudices which could be left unquestioned.

It also enlarges the philosopher's worldview above occupation with self and turns thus into a way of life, enhancing relationships with others. Philosophy, Russell claims,

"makes us citizens of the universe."



The Problems of Philosophy challenges commonsense ideas such as truth, knowledge, falsehood and the connection between appearance and reality. He asserts that much of what passes for knowledge is simply opinion on probabilities supported by a degree of confidence. Commonsense is useful in everyday life, but it is not precise. Russell notes that it is difficult to determine whether:

"...even the strangest hypotheses may not be true."

One major problem the author perceives with commonsense is that it varies with cultural changes. In the time of Descartes and Leibnitz God's existence was a general cultural assumption. Consequently, some beliefs were accepted as philosophical truisms, such as Leibnitz's concept that objects consist of souls or Berkeley's idea that objects exist in the mind of God. Again, Kant assumed that infinity did not exist and concluded that space and time were thus impossibilities.

Russell himself was caught out by his own cultural commonsense assumptions when he posited that space and time are infinitely divisible. This occurred because the quantum theory of time in 1911 was not fully accepted.


Russell asserts that nothing is self-evident, except sense-data, so that some kind of axiomatic logic must be applied to gain knowledge. (True sceptics might question this, too, as reasoning is a form of knowledge.)

At the same time Russell admits that absolute scepticism is very limiting:

"if we adopt the attitude of the complete sceptic ... we are demanding what is impossible."

The author proposes a cartesian systematic doubt which questions prejudices and assumptions. The aim is not to demolish knowledge but to fortify it through finding fundamental beliefs on which to establish knowledge:

"consider each piece of apparent knowledge... and retain whatever still appears to be knowledge when this consideration is completed." 

Questions and Answers

Russell considers that, contrary to the physical sciences, philosophy has answered few of the questions it posed. He expresses scepticism on the philosophical claims of the proofs of God's existence, the inexistence of evil or the unreality of matter. Many philosophers' assertions are based on uncritical preconceptions of their time.

He is critical, for instance of Descartes' conclusion "I think therefore I am.", because the I is difficult to define with precision. He also reprimands Berkeley for his 'mind of God' explanations about the existence of matter, Hume's extreme scepticism and Kant's unproven assertions about a priori knowledge.

Despite philosophy failing to offer conclusive answers Russell still values philosophical thought. It broadens the mind, encourages curiosity about the world and shows us how much we do not know. He believes that these are references which will help society to flourish.


The Problems of Philosophy is basically concerned with the philosophical study of knowledge: how do we know? Russell's text is inspired by the age-old debate, which may be traced back to Plato and Aristoteles, between rationalists, who hold that some knowledge is innate or a priori, and independent of sensory experience, and empiricists, who hold that all knowledge derives from the senses.

Both Descartes and Leibnitz maintained that knowledge is rational, with no influence of sense experience. This allowed them to construct metaphysical arguments for the nature of reality. Descartes inferred the existence of God, for example, as a reality outside his ideas, 

In The Problems of Philosophy Russell mentions the empiricists Berkeley (1685–1753), Locke (1632–1704) and Hume (1711–76). They rejected Descartes' concept of innate knowledge which was refined by Leibnitz. 

Locke argued that the mind is a blank slate on which experience writes knowledge. 

Berkeley states that an idea is a collection of sensations which inform us about objects, so that knower actually only perceive ideas. An object, then, is the idea that the mind has of it. He concludes that there is no world apart from our (and God's) ideas of it. 

Hume considered that knowledge derives from impressions. However, if knowledge comes from impressions and the knower has an idea which cannot be related to initial impressions, then that idea is unjustifiable. Hume gives causation as an example. Connecting two events though cause and effect is not rationally justified, he says, because neither deduction nor induction reasoning can relate them since cause cannot be traced back to an initial sense impression. Causation is accepted because it is a habit of commonsense experience, not a rational conclusion. It exists to enable connections between past and present.

Russell concludes that many commonsense inferences may be impossible to prove, but adds that the empiricists' explanations are more complicated and often less plausible than commonsense.

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