Problems of Philosophy

Our knowledge of things is attainable in two ways: knowledge by acquaintance and knowledge by description. Our knowledge by acquaintance entails an immediate awareness of our own sense-data. From this acquaintance, we are directly aware of a thing without any inference. Knowledge by acquaintance is logically independent of any knowledge of truths. Knowledge by description is predicated on something with which we are acquainted, sense-data, and some knowledge of truths, like knowing the description: "such-and-such sense-data are caused by the physical object." Thus, knowledge by description allows us to infer knowledge about things we have never experienced via things with which we have had direct acquaintance.

Idealism is the philosophical view that "whatever exists, or at any rate, whatever can be known to exist, must be in some sense mental." Russell rejects idealism because he believes the arguments for idealism to be based on fallacious reasoning. The arch-idealist, Bishop Berkeley, refers to two different things using the same word, "idea." One is the thing of which we become aware and the other is the actual act of apprehension. While the latter act seems obviously mental, the former "thing" does not seem so at all. Russell holds that idealists mistake the object sense of "idea," with the apprehensive, mental sense. Instead, Russell advocates a theory of knowledge where things exist independently of our minds and are constituted in the physical world of matter.

Russell believes that objects in the physical world, like his famous table, are composed of matter. These are particulars. They exist in one place at any given time and exemplify universals. The universal is an ideal from which particulars derive their common essence. Universals include qualities, properties, and relations. A white sheet of paper is a particular that exemplifies the universal "whiteness," which is common to all white things. A particular may be known by way of our acquaintance with sense-data. We grasp universals through a process of induction from particulars.