Knowledge, concept of

1. The varieties of knowledge

Knowledge comes in many varieties. I can know how to adjust a carburettor. I can know a person. I can know that mixing bleach and ammonia is dangerous. In the first case, I possess a skill. In the second, I am acquainted with someone. In the third, I know a fact. Epistemologists have differed on the relationships between these types of knowledge. On the one hand, it could be held that knowing a person (place or thing) should be construed as nothing more (or less) than knowing certain facts about that someone and possessing the skill of being able to distinguish that person from other objects. On the other hand, it has been held that knowing facts depends upon being acquainted with particular objects. Whether the reduction of one form of knowledge to another is ultimately successful is an area of contention among epistemologists (see Knowledge by acquaintance and description).

Nevertheless, it is knowledge of facts, so-called propositional knowledge, as opposed to knowledge by acquaintance or the possession of skills, that has been the central concern of epistemologists. The central question can be put this way: which beliefs of mine are to be counted as knowledge? This question presupposes that knowledge is a species of belief, but some might think that knowledge and belief are mutually exclusive: for example, we say such things as ‘I do not believe that; I know it’. But we also say such things as ‘I am not happy; I am ecstatic‘. A suggested paraphrase of this expression seems to capture what is meant without denying the obviously true claim that ecstasy is a form of happiness. The paraphrase is: I am not merely happy, I am ecstatic. The parallel is: I do not merely believe it; I know it. Thus, this type of linguistic evidence does not support the suggestion that belief and knowledge are mutually exclusive. In general, epistemologists have held that propositional knowledge is a species of belief.