The origin and nature of ‘belief’ was Russell’s central philosophical preoccupation throughout his long life. In The Problems, he delineates five different causes which are:

  1. A spontaneous unconscious inference between a world like ‘fire’ and a physical, verbal, visual or psychological reaction to it. In this respect, such a belief can be found in animal as well as human behaviour as in the case of a cat rushing to his mistress every time the latter calls out the word ‘fish’ to signal feeding time.
  2. A memory-belief, as my looking at a photograph which causes my present remembering of a past event, the actuality of which being irrelevant to the existence of that belief, i.e.: I am convincing myself that I can remember the actual circumstances surrounding the taking of that picture but I may be holding a ‘false’ memory-belief. The assumption, held in The Problems, that memory can make us ‘directly’ acquainted with past events was later rejected along with mental acts.
  3. An expectation, which can be a general order as in ‘I will be a year older on my next birthday’ or specific, as in waiting for the 10.45 train to London, as scheduled in the official railway timetable.
  4. The testimony of other people which establishes my belief in a public world, through ‘analogy’ since it is through my repeated observation that I am inclined to believe that other people have similar experiences to mine.
  5. A conscious inference as in discovering my friend’s umbrella left behind in my house

The late Russell was still committed to a correspondence theory of truth, characterised by ‘true’ or ‘false’ relations obtaining between a belief and one or more facts. When such a reaction is absent, the belief is false. In An Outline of Philosophy, Russell had laid out the question of truth and falsehood into the following subdivision:

  1. Formal Theory: Given the meanings of the component words, what decides whether a sentence is true or false?
  2. Causal Theory: Can we distinguish between truth and falsehood by (a) their causes, (b) their effects?
  3. Individual and Social Elements: A statement is a social occurence, a belief is something individual. How can we define a belief, and what is it when not composed of words?
  4. Consistency and Truth: Can we get outside the circle of beliefs or statements to something else which shows them true, not merely consistent? In other words, what possible relation is there between propositions and facts?

Despite his numerous attempts at trying to resolve the elusive inconsistencies seemingly inherent in any theory of knowledge, Russell remained, at the end of his life, just as frustrated about his contribution to the problem as he had been, in the 1910’s, regarding the possibility of founding a new, flawless system of logic. In The Problems, the philosopher put great emphasis on the principle of induction as he saw it at work in ‘the general principles of science’ as well as ‘the beliefs of everyday life’. However, throughout his academic career, he persisted in proclaiming that ‘all inferred knowledge is at best probable’ as the inductive principle cannot ultimately be proved nor disproved by experience.