Quote from one highly unconventional modern philosopher:
Most men spend their days struggling to evade three questions, the answers to which underlie man's every thought, feeling and action, whether he is consciously aware of it or not: Where am I? How do I know it? what should I do?
By the time they are old enough to understand these questions, men believe that they know the answers. Where am I? Say, in New York City. How do I know it? It's self-evident. What should I do? Here, they are not too sure—but the usual answer is: whatever everybody does. The only trouble seems to be that they are not very active, not very confident, not very happy—and they experience, at times, a causeless fear and an undefined guilt, which they cannot explain or get rid of.
They have never discovered the fact that the trouble comes from the three unanswered questions—and that there is only one science that can answer them: philosophy.
Philosophy studies the fundamental nature of existence, of man, and of man's relationship to existence. As against the special sciences, which deal only with particular aspects, philosophy deals with those aspects of the universe which pertain to everything that exists. In the realm of cognition, the special sciences are the trees, but philosophy is the soil which makes the forest possible.
Philosophy would not tell you, for instance, whether you are in New York City or in Zanzibar (though it would give you the means to find out). But here is what it would tell you: Are you in a universe which is ruled by natural laws and, therefore, is stable, firm, absolute—and knowable? Or are you in an incomprehensible chaos, a realm of inexplicable miracles, an unpredictable, unknowable flux, which your mind is impotent to grasp? Are the things you see around you real—or are they only an illusion? Do they exist independent of any observer—or are they created by the observer? Are they the object or the subject of man's consciousness? Are they what they are—or can they be changed by a mere act of your consciousness, such as a wish?
The nature of your actions—and of your ambition—will be different, according to which set of answers you come to accept. These answers are the province of metaphysics—the study of existence as such or, in Aristotle's words, of "being qua being"—the basic branch of philosophy.
No matter what conclusions you reach, you will be confronted by the necessity to answer another, corollary question: How do I know it? Since man is not omniscient or infallible, you have to discover what you can claim as knowledge and how to prove the validity of your conclusions. Does man acquire knowledge by a process of reason—or by sudden revelation from a supernatural power? Is reason a faculty that identifies and integrates the material provided by man's senses—or is it fed by innate ideas, implanted in man's mind before he was born? Is reason competent to perceive reality—or does man possess some other cognitive faculty which is superior to reason? Can man achieve certainty—or is he doomed to perpetual doubt?
The extent of your self-confidence—and of your success—will be different, according to which set of answers you accept. These answers are the province of epistemology, the theory of knowledge, which studies man's means of cognition.
These two branches are the theoretical foundation of philosophy. The third branch—ethics—may be regarded as its technology. Ethics does not apply to everything that exists, only to man, but it applies to every aspect of man's life: his character, his actions, his values, his relationship to all of existence. Ethics, or morality, defines a code of values to guide man's choices and actions—the choices and actions that determine the course of his life.
Just as the astronaut in my story did not know what he should do, because he refused to know where he was and how to discover it, so you cannot know what you should do until you know the nature of the universe you deal with, the nature of your means of cognition—and your own nature. Before you come to ethics, you must answer the questions posed by metaphysics and epistemology: Is man a rational being, able to deal with reality—or is he a helplessly blind misfit, a chip buffeted by the universal flux? Are achievement and enjoyment possible to man on earth—or is he doomed to failure and disaster? Depending on the answers, you can proceed to consider the questions posed by ethics: What is good or evil for man—and why? Should man's primary concern be a quest for joy—or an escape from suffering? Should man hold self-fulfillment—or self-destruction—as the goal of his life? Should man pursue his values—or should he place the interests of others above his own? Should man seek happiness—or self-sacrifice?
I do not have to point out the different consequences of these two sets of answers. You can see them everywhere—within you and around you.
The answers given by ethics determine how man should treat other men, and this determines the fourth branch of philosophy: politics, which defines the principles of a proper social system. As an example of philosophy's function, political philosophy will not tell you how much rationed gas you should be given and on which day of the week—it will tell you whether the government has the right to impose any rationing on anything.