This chapter is an eloquent vindication for the practice of philosophy. Russell explicitly addresses the "practical man" who only recognizes philosophy as a pursuit of "hair-splitting distinctions" and irrelevant trifling. Viewing philosophy thus is a result of having a "wrong conception of the ends of life" and "the kinds of goods which philosophy strives to achieve." Russell contrasts the utility of philosophy with that of the physical sciences. Scientific study has far-reaching effects on mankind, through inventions, while philosophic study primarily affects the lives of those who study it, and only indirectly affects others through them. The principal value of philosophy is thus to be found in its disciples. Russell would have his reader free her mind of practical prejudices. Whereas the practical man would only attend to food for the body and material needs, the philosophic attitude also recognizes the need for food for the mind.
The aim of philosophy is the achievement of knowledge through criticism, "which gives unity and system to the body of sciences." However, philosophy does not maintain a substantial body of definite knowledge in the sense that history, mathematics, or the physical sciences do. Part of the reason why philosophy does not bear such a body of evidence is because when definite knowledge on a subject becomes possible, it splits off forming another discipline. Study of the heavens, of natural sciences, and the human mind originated in philosophic investigation and now assume the figures of astronomy, physics, and psychology. Thus, with respect to definite answers, "the uncertainty of philosophy is more apparent than real."
Yet, part of the uncertainty in philosophy derives from the very nature of the questions that it undertakes to answer. These questions address most profound human interests: "Has the universe any unity of plan or purpose, or is it a fortuitous concourse of atoms? Is consciousness a permanent part of the universe, giving hope of indefinite growth in wisdom, or is it a transitory accident on a small planet on which life must ultimately become impossible? Are good an evil of importance to the universe or only to man?" Besides the magnitude of these questions, the various answers which philosophy suggests are usually not "demonstrably true." Still, the pursuit of philosophy is not merely to suggest answers to these questions but to make us sensitive to their importance and to keep us conscious of a "speculative interest in the universe," which we might otherwise forget.
Even though some philosophers have developed programs of thought that do offer a definite set of conclusions about religious belief, human knowledge, and other issues, Russell urges that such attempts are usually unwise dogmatic declarations. Consistent with the thought of his other chapters, he claims that we cannot hope for definite answers or even high degrees of certainty.
In fact, he theorizes, the value of philosophy appears in its very uncertainty. He persuasively writes, "the man who has no tincture of philosophy goes through life imprisoned in the prejudices derived from common sense, from the habitual beliefs of his age or his nation, and from convictions which have grown up in his mind without the co-operation of consent of his deliberate reason." This way of thinking is closed to speculation or theory about possibility. Philosophizing, on the other hand, allows us to see even the most ordinary things in unfamiliar light. Though such consideration diminishes our faulty certainty about the world, it suggest numerous possibilities "which enlarge our thoughts and free them from the tyranny of custom." Though we lose a little of our confidence as to what things are, we gain knowledge of what they may be. Philosophy banishes "arrogant dogmatism" and liberates "our sense of wonder."
Philosophic thought also has a value by virtue of the things it contemplates and the distinctness of those things from "personal aims" and "private interests." Philosophy lets in the outside world and enlarges out interest. Russell writes, "in one way or another, if our life is to be great and free, we must escape this prison" of our private world. Russell's belief is that everything that depends on the private world "distorts the object" of contemplation and prevents the union of the object and the intellect. Philosophic contemplation sponsors this escape by enlarging the Self. Russell holds that the primary value of philosophy is not in any kind of definite answer, but exists in the questions themselves. He concludes that, "through the greatness of the universe which philosophy contemplates, the mind also is rendered great."