Bertrand Russell’s The Problems of Philosophy is an introduction to some of the central issues in metaphysics and epistemology. The work is still regarded as one of the best introductions to philosophy, and it is also historically significant as one of the first book-length examples of analytic philosophy, the type of philosophy founded by Russell, his Cambridge colleague G. E. Moore, and German mathematician Gottlob Frege.
Analytic philosophy is distinguished by its emphasis on clarity and the attempt to establish its conclusions by the strongest rational means possible. While the book deals with a number of philosophical issues, much of it is centered on the problem of the external world and the problem of a priori knowledge—that is, knowledge that in principle can be gained through thought alone, independent of empirical experience.
Russell begins by asking whether there is any knowledge that is so certain that no reasonable person can doubt it. While it may seem obvious that there is such knowledge, Russell shows that it is not easy to arrive at an adequate answer to this question. Take for example an ordinary table. It is usually taken for granted that sensory experience reveals what the table is like: that it is brown, smooth, rectangular, and so forth. This seeming obviousness, however, ignores, for example, that the table may not look uniformly brown. As a perceiver changes location, the color of the table will appear to change. The same is true for all of the properties of the table apprehended through sensory experience: They may seem stable, but they are in fact alterable based on the situation and attitude of a perceiver. While this fact is usually ignored in everyday life, it is vitally important to a philosopher trying to determine whether sensory experience yields genuine knowledge of the external world. Physical objects can appear to have incompatible properties: A table that appears to be smooth to the naked eye may appear to be rough when viewed under a microscope. However, Russell believes, physical objects cannot really have incompatible properties; thus, it seems to him that perception can reveal only how things appear and not how they really are.
Based on considerations such as these, many philosophers have adopted attitudes of either skepticism (the real world is unknowable) or idealism (the world is essentially mental). Russell argues that drawing either a skeptical or an idealist conclusion is not mandatory. His first step in this argument is to introduce the concept of sense data, or the things that are immediately known in sensation. Colors, sounds, smells, and so forth are examples of sense data. Russell is careful to distinguish sense data from sensation, which is the mental act of being aware of sense data. Without this distinction, there is a tendency to think that the only things that can be known or can exist are mental, and this tendency leads to either skepticism or idealism.
Russell next asks about the relation between sense data and mind-independent physical objects. While skeptical arguments may demonstrate that the existence of physical objects can be denied without contradiction, Russell argues that there are good reasons for thinking that such objects do exist. His argument begins with the fact that the patterns of sense data experienced by the mind are not totally chaotic but are, rather, relatively coherent. This fact requires an explanation, and, according to Russell, the best explanation is that the sense data are caused by the interaction of physical objects and a person’s sense organs. This interaction ultimately causes the person to be aware of a particular pattern of sense data. Thus, since positing the existence of physical objects provides the best explanation for the patterns of sense data that are experienced by humans, it is reasonable to believe that there is an objective world of mind-independent physical objects.
(The entire section is 1615 words.)