Good Reasons for Knowing Something

TOK is concerned with assessing which kinds of reasons are good reasons for knowing something. Here is a list of some of the most commonly stated reasons for knowing something, although not all of them are actually reliable:


1.       I know that grass is green, because I can see it. Sense perception is the evidence for our knowledge about the world.


2.       I know that the sum of any two odd numbers is always an even number, because I can prove it. Reason in the sense of Logic is the basis of our analytic knowledge.


3.       I know that it is wicked to torture a person, because my intuition tells me so. Knowledge of right and wrong is often based on such inner convictions of certainty and mystics and transcendentalists in particular rely on this sort of reason.


4.       I know that I have a headache, because I feel it. Self-awareness, or introspection, is the basis for knowing one’s own “self-presenting” states. If I were to say to you, I wish it would rain; or, I feel drowsy, you would not ask me, how do you know? One’s wishes, feelings, thoughts, hopes, and so on seem to be self-evident; they do not have to be inferred from something else in order to be known.


5.       I know that I walked home yesterday, because I remember it. Knowledge of the past begins on the basis of memory. But memory is of course no guarantee of truth. David Hume long preceded Sigmund Freud in claiming that remembered events differ from imagined events only in being more vivid. To verify a memory, one can compare it only with another memory: the past event cannot be hauled forth and compared with the present recollection. So there is no way to avoid a certain degree of skepticism. Descartes said that our memories may all have been breathed into us by a malicious demon; and Russell, in a well-known passage in The Analysis of Mind, asserts:


Everything constituting a memory-belief is happening now. It is not logically necessary … that the event remembered should have occurred, or even that the past should have existed at all. There is no logical impossibility in the hypothesis that the world sprang into being five minutes ago, exactly as it then was, with a population that “remembered” a wholly unreal past … nothing that is happening now… can disprove [that] hypothesis.


But a totally delusive memory is not what is meant by memory at all; just as there can be no “counterfeit coins” unless at least some coins are genuine, so a memory can be “erroneous” only if at least some memories are truthful. Undoubtedly we do in fact recall our past selectively; under hypnosis we recover forgotten experiences; we edit our memories, more or less deliberately. But all empirical knowledge is likewise selected and edited. Indeed, what is meant by “the present”? Literally, it is a dimensionless mathematical point, constantly vanishing. James called it “specious” and estimated that one can actually attend to a “present” time span of about twelve seconds. In this phenomenological sense, one may perceive as a unit a sentence, or a melody, or a chain of reasoning. A work of art likewise focuses the observer’s attention on an extensive complex of sights or sounds so composed that it is experienced in a timeless present.


6.       I know that the velocity of light is 186,000 miles per second, because the physicists say so. We often rely on authority (Bacon’s “idols of the theatre”). Of course, we should accept someone as an authority only if he can himself produce other types of good reasons, which we all can in principle examine. Authority as a justification for knowledge is worthless if it cannot be dissolved into its ingredients.


7.       I know that the number thirteen is unlucky, because everybody says so, something more technically known as consensus gentium.


8.       Joan of Arc knew that she would lead the French army, because God revealed this to her. Revelation as a justification for knowledge seems to me (unless I receive one) unverifiable and unreliable.


9.       St. Thomas knew that he would be resurrected after his death, because he had faith. Let no one make the disastrous error of confusing faith with knowledge, or relying upon faith as a reason for knowledge. Faith is an attitude of belief and belief is necessary for knowledge, but belief / faith along is not sufficient; just because you believe / have faith in something that does not make it so. To call belief “faith” does not improve it, whether that faith be in God, or in Jupiter, or in Destiny, or in human nature.


In summary five of these reasons seem to be good reasons: sense perception, logic, intuition, self-awareness, and memory, the rest should be treated with extreme caution and skepticism when regarded as ways of knowing.


Adapted from Reuben Abel’s ‘Man is the Measure’ (Chapter 2)