Reading notes from 'The Problems Of Philosophy', by Bertrand Russel.

Appearance and reality#

  • Is there any truly undoubtable knowledge in the world?
  • Philosophy is us attempting to answer ultimate questions without dogma, but critically.
  • The real table is not what we immediately experience through our senses. Is there a real table, and if so, what kind of object is it?
  • sense-data is everything immediately known to the senses. The table, if it exists, is called a physical object.
  • does matter exist? If so, what is it's nature?
  • Idealism: The immediate objects of our senses not existing independently of us. There is nothing real except minds and ideas.
  • Idealists acknowledge matter exists at the same time as they deny it.

The Existence Of Matter#

  • Does the table even exist?
  • We are at least certain of our immediate sense-data.
  • Descartes method of systematic doubt. He arrived at the point where he doubted everything but his own existence, given the fact that he was doubting. "I think, therefore I am".
  • It is particular thoughts and feelings that have primitive certainty. Not the "I".
  • Other people are also represented by sense-data.
  • In a way, we can only prove the existence of ourselves and our experiences. Or we can hypothesize that it's all a dream. But this is unnecessary complexity. It is simpler to hypothesize that there are objects that are not us and their actions on us cause sensations.
  • This is an instinctive belief that simplifies and systematizes our experience.
  • Knowledge is built on instinctive beliefs and if those are rejected, nothing remains.

The Nature Of Matter#

  • The physics answer: objects live in the physical space and may be thought of as causing our sensations.
  • The space of science is not identical to the spaces we see and feel, though connected.
  • We can't sense an object unless we and the object are both in the same physical space.
  • We assume that The spatial relations of objects in space correspond to our sense-data.
  • while we know the relations of distances between objects in space, we can't know about the distances themselves.
  • While our feeling of duration, or the passage of time, is subject again to private time public time, if time consists of an order of before and after, the order we sense is the same as the order in physical space.
  • The intrinsic nature of objects remains unkown even if their relational properties are knowable through sense-data.
  • Idealists: whatever we can know about must be in our minds. At the same time they don't deny our sense-data as signs that something exists outside our private sensations.


  • Whaveter is known to exist is in some sense mental.
  • All immediate data are "ideas", Objects exist in essnce because they are being perceived. They continue to exist because "God" watches them.
  • But, we can't say that objects are in our mind, only that thoughts of objects are.
  • Separating the sense of color (that a certain color will exist given a normal eye and under specific conditions), from our awareness of that color.
  • Knowledge is acquired by the mind familiarizing with things other than itself.
  • Knowledge of truths vs knowledge of things.

Knowledge by acquaintance and Knowledge by description#

  • By acquaintance - we are directly aware of the object.
  • By descripton - we know of a description of the object, not the object directly.
  • By memory - the past by inference.
  • By self-consciousness - being aware of being aware of something
  • We seem to always come back to a consciousness of particular thoughts and feelings when we try to "find" our "Self".
  • It is probable, that we can sense the Self, as aware of things and having desires towards things.
  • We also have acquaintance with concepts: general ideas like truth, love, diversity.
  • By description: knowing that an object exists having a certain property or set of properties, not acquainted with it. E.g. Names of places, or famous people.
  • Fundamentally, every proposition we can come up with, must be made of parts we are acquainted. When we make a proposition about Julius Caesar (whom we can't be acquainted), we are accessing knowledge by description. That description is itself composed of parts we are acquainted with.
  • Knowledge by description is important because through it we can move beyond the limits of our private experience.

On Induction#

  • We are all convinced the sun will rise tomorrow.
  • The principle of Induction
    • The greater the number of cases A is associated with B, (and B is not dissociated from A) the more probable they will be associated in a fresh case.
    • Under same circumstances, more cases of association increase certainty of probability of association, until made certain
  • The inductive principle cannot be disproved or proven by appeal to experience.

On Our Knowledge of general principles#

  • Similar to how induction cannot be proven by experience, there are other principles that can't.
  • Examples: Identity (whatever is, is), contradiction (nothing can both be and not be), Excluded middle (everything either is or isn't)
  • There are also principles that don't deal with certainty, but rather with probability
  • The empiricists: all knowledge is derived from experience.
  • The rationalists: in addition to experience, there are certain "ideas" we know independently of it.
  • Logical principles are known to us outside of experience. All proof presupposes them
  • Called a priori knowledge
  • nothing can be known to exist without help from experience. E.g. knowning the president of US exists.
  • But, Given the above, The scope and power of a priori general principles is limited
  • Yet, A priori knowledge is not only logical. It also includes knowledge about ethical (intrinsic) value.
  • A priori in the sense that it's truth cannot be proven or disproven by experience. That a thing exists or doesn't doesn't prove that it is good or bad that it exists or it doesnt'.
  • Deduction is better suited for a priori general propositions. Induction is preferrable in empirical generalizations, e.g. all men are mortal.
  • Kant was the first to ask: how is it possible for a priori knowledge to exist? How can it exist in the general?

How A Priori Knowledge Is Possible#

  • Kant is credited with perceiving a priori knowledge in addition to our analytic knowledge and also for making theory of knowledge necessary.
  • Hume argued that nothing can be known a priori about causality. that it is a synthetic connection. but Kant proved that all pure mathematics are a priori. Which shifted the question to how is pure mathematics possible?
  • Empiricists view was that pure math is possible by pure induction. But you can't prove the inductive principle via induction. Pure mathematics is general knowledge whereas all experience is particular.
  • Kant considers sense-data comes from the object and we supply the space/time and relations between sense-data.
  • The physical objet is considered unknowable. Our experience is the product of our sense-data and us (and our a priori knowledge.).
  • But, our nature, thought to provide the a priori knowledge, is as much part of the world as anything and it is not a constant.
  • Also, if a priori knowledge is "truth", it should apply to objects even when we don't think of them.
  • Example given is the law of contradiction.
  • There is the belief that relations like "I am in my room" are the works of the mind, of pure thought. Relations are in a world neither physical nor mental.

The World Of Universals#

  • Plato arrived at the world of ideas, beyond our senses. E.g. take justice. All acts of justice partake in some common nature, or virtue. That would be justice itself, the essence, which, when mixed with life, produces just acts. This essence is called "idea" or "form".
  • The word universal is used in favor of the word idea.
  • Knowledge involves universals.
  • For Plato, we can only talk about the world of the senses through the world of ideas.
  • He feels Universals in themselves are incomplete and demand context.
  • Monism: properties of single things, no relations between things. Thus, one thing in the univrse.
  • Monadism: many isolated things (monads) that cannot interact substantially.
  • The mistake they made was thinking only of qualities as being universal. But what about relations?
  • If A is north of B, that relation is independent of thought, understood but not created by thought.
  • The "north of" relation cannot be found in space and time. Universals are not thoughts, though they can be the objects of thoughts.
  • The world of universals can be seen as a world of being, being having a timeless component when constrasted with existence. Unchangeable, exact, rigid. Contrast with the world of existence, a fleeting vague. But also containing all thought, feeling, data, physical objects.
  • Both worlds (universals and senses) demand our attention.

On Our Knowledge Of Universals#

  • Universals are also divided into those known by acquaintance and description.
  • Qualities: We are acquainted with all the universals we can find examples of in our sense-data.
  • Relations: Understanding how the components of a complex object fit together.
  • All a priori knowledge deals only with relations among universals.
  • All applications of the general a priori proposition to particulars, involve experience, therefore an empirical element.
  • The difference between a priori vs empirical generalization ,where evidence is particular instances.

On intuitive Knowledge#

  • There is this idea that everything we believe should be capable of proof. That belief without reason is unreasonable belief.
  • But, We can dive into our reason for beliefs by induction but we can't regress further. It is the "logical end".
  • Other general principles too are self-evident like that.
  • Particular instances of the general principle are more evident.
  • Truths derived from sensation are also self-evident, but also different than the sense-data that produced them.
  • There are assertions of existence, "I see a patch of red" but also complex, where we also judge the relations between different aspects of an object, e.g. a circle of red patch.
  • Judgments of memory. Vividnes and proximity in time. We could say that memory has degrees of self-evidence. But there are cases where a belief from memory is false.
  • Generally, there are degrees of self-evidence. This is important, because if propositions have a degree of self-evidence we we are to keep the most self-evident proposition.

Truth And Falsehood#

  • We may believe what is false as well as what is true. how false beliefs are to be distinguished from true beliefs?
  • But before that: What do we mean by truth and falsehood?
  • To discover the nature of truth, out theory must: account for false. A world of pure matter contains no truths and no falses.
  • Although truth and falsehood are properties of beliefs, they depend on relations of beliefs to other things, not on some internal quality of the beliefs.
  • Truth encompasses correspondence between belief and fact.
  • Another definition is truth consists of Coherence. But, for example, in science there are more than one hypotheses that explain a phenomenon.
  • While the laws of logic are used to test coherence, they cannot be established by this test.
  • Thus a belief is true when it corresponds to a certain associated complex whole, and false when it does not.
  • While Beliefs depend on minds for their existence, they do not depend on minds for their truth.

Knowledge Error And Probable Opinion.#

  • How can we know what is true and what is false?
  • a true belief is not knowledge when it is deduced from a false belief.
  • a true belief is not knowledge when it is deduced by a fallacious process of reasoning
  • What we firmly believe, if it is true, is called knowledge, provided it is either intuitive or inferred (logically or psychologically) from intuitive knowledge from which it follows logically.
  • Much of what commonly passes as knowledge is more or less probable opinion.
  • A body of individually probable opinions, if they are mutually coherent, become more probable than any one of them would be individually
  • the mere organization of probable opinion will never, by itself, transform it into indoubtable knowledge.

The Limits Of Philosophical Knowledge.#

  • The Grandfather of Philosophical systems: Hegel.
  • Hegel's thesis: everything but the Whole is obviously fragmentary, and incapable of existing without the complement supplied by the rest of the world
  • Assumes the incomplete must be not self-subsistent, but must need the support of other things before it can exist.
  • But, The fact that a thing has relations does not prove that its relations are logically necessary.
  • We cannot prove that the universe as a whole forms a single harmonious system such as Hegel believes that it forms.
  • The attempt to determine the universe by means of a priori principles has broken down;
  • The whole tendency of modern thought, is in showing that supposed contradictions were illusory, and that very little can be proved a priori from considerations of what must be.
  • The essential difference of philosophy from science, is critical examination of the principles employed in science and in daily life; searching for inconsistencies, and only accepts what, has not reason for rejecting upon critical examination.
  • The aim of criticism is considering each piece of apparent knowledge on its merits, and retaining whatever still appears to be knowledge when done.
  • Philosophy may claim justly that it diminishes the risk of error, and sometimes, renders it negligible. Not much more.

The Value Of Philosopy.#

  • Utility does not belong to philosophy.
  • It's value is indirect, through its effects upon the lives of those who study it.
  • To a great extent, the uncertainty of philosophy is more apparent than real: definite answers are placed in the sciences, indefinite ones remain to form the residue which is called philosophy.
  • The value of philosophy is in its very uncertainty.
  • Offers possibilities that widen our thoughts and free them from the tyranny of custom.
  • When you become used to the freedom and impartiality of philosophic thought you will preserve those traits in the world of action and emotion.

Further Reading#

He recommends reading

  • Plato: Republic, especially Books VI and VII.
  • Descartes: Meditations.
  • Spinoza: Ethics.
  • Leibniz: The Monadology.
  • Berkeley: Three Dialogues between Hylas and Philonous.
  • Hume: Enquiry concerning Human Understanding.
  • Kant: Prolegomena to any Future Metaphysic.