Bertrand Russell's The Problems of Philosophy, first published in 1912, grapples with fundamental questions concerning the nature of knowledge and reality. A central concern throughout the work is the apparent disparity between how things seem to us (appearance) and what they truly are (reality). Russell meticulously argues that our immediate sensory experiences, while undeniably real to us, do not necessarily provide direct access to the objective, external world. Instead, he posits that sense-data are private and subjective, leading to a philosophical problem: how can we bridge the gap between our individual perceptions and a shared, objective reality? Russell's solution involves a nuanced distinction between the data of sense and the physical objects that cause them, ultimately suggesting that scientific inference, rather than direct intuition, is key to understanding the world beyond our immediate awareness.
Russell begins by examining the case of a table. When we look at a table, we perceive it as having a particular color, shape, and texture. However, he observes that these qualities change depending on our perspective. From one angle, the table appears brown; from another, it may seem a different shade. The surface that appears smooth might reveal a rough texture upon closer inspection. These variations, Russell contends, mean that the "brownness" or "smoothness" we directly perceive cannot be an intrinsic property of the table itself. Instead, these are sense-data, private experiences unique to each observer. The table, as a physical object existing independently of our perception, must possess properties that are consistent and objective, even if those properties are not directly apparent to our senses. The “real” table, therefore, is not the collection of appearances but rather the underlying physical entity that gives rise to these varied sense-data.
This leads Russell to the problem of the existence of matter. If our sense-data are private and variable, how can we be sure that there is an external world of physical objects causing these sensations? Russell acknowledges the skeptical implications of this line of reasoning. However, he argues against solipsism, the belief that only one's own mind is sure to exist. He proposes that the most reasonable explanation for the consistency and regularity we observe in our sensory experiences, and especially the agreement between different observers' perceptions, is the existence of an external world. While we cannot directly perceive this world, we can infer its existence through what he calls the "argument from analogy." Just as we infer that other people have minds similar to our own because they behave in ways analogous to how we do, we infer the existence of physical objects because our sense-data are caused by something external and consistent.
Russell further distinguishes between "knowledge by acquaintance" and "knowledge by description." We have direct, immediate knowledge by acquaintance of our own sense-data and our own mental states. We know the feeling of warmth, the color red, or the emotion of joy directly. However, our knowledge of the external world, of physical objects, and even of other minds, is largely knowledge by description. We know that there is a table because we can describe its properties and its causal relationships with our perceptions. This knowledge is indirect, mediated by inference and the structure of our beliefs about the world. The "real" table is not the sense-data of brownness or smoothness, but rather the entity that has the properties required to produce those sense-data under specific conditions.
In conclusion, Bertrand Russell's exploration of appearance and reality in The Problems of Philosophy highlights a crucial epistemological challenge. He skillfully demonstrates that our immediate sensory experiences, the data of sense, are subjective and variable. This subjectivity makes a direct grasp of objective, external reality impossible. Russell's philosophical approach steers away from outright skepticism by advocating for an inferential understanding of the external world, grounded in the regularity of experience and the principle of analogy. The "real" world, for Russell, is a construction of scientific reasoning, a hypothesis that best explains the consistent patterns we observe, even if it remains forever beyond our direct sensory acquaintance.