Distinction in our ways of knowing things, highlighted by Russell and forming a central element in his philosophy after the discovery of the theory of definite descriptions. A thing is known by acquaintance when there is direct experience of it. It is known by description if it can only be described as a thing with such-and-such properties. In everyday parlance, I might know my spouse and children by acquaintance, but know someone as ‘the first person born at sea’ only by description. However, for a variety of reasons Russell shrinks the area of things that can be known by acquaintance until eventually only current experiences, perhaps my own self, and certain universals or meanings qualify. Anything else is known only as the thing that has such-and-such qualities. See also logical atomism.