The word "philosophy" comes from the Greek philos (loving) + sophos (wise) meaning literally love of wisdom. But that doesn't tell us much. (And what, exactly, is wisdom?) A better way of getting at the nature of philosophy is to ask about what it deals with (subject matter) and what it is that philosophers (or anybody else) do when they are doing philosophy (method).
The subject matter of philosophy is closely connected with the sorts of questions that have dominated philosophical investigation.
Metaphysics is a systematic attempt to answer the question: What is reality? The ancient Greek philosophers were very interested in this question and advanced a number of theories to try to answer it.
Some philosophers (materialists) have thought that reality is essentially material in nature. Others (idealists) have claimed that reality is essentially mental or spiritual. For those who believe the common sense view that both mind and matter are basic kinds of stuff comprising reality, what is the connection between them? Do they interact, and if so, how? Or is the mind really the same as the (material) brain? Can machines (computers) be conscious? Is there life after death?
Metaphysics also gives rise to the cosmic question: how did the universe come to be, and why is there something rather than nothing? And closely connected to the question of the nature of reality is the question of God's existence. Does reality include such a being, i.e. is there a God? What is God like? And what is God's relation to the rest of reality? And if there is a God, i.e. a being which is all-powerful, all-knowing and all-good—we encounter the problem of evil: how can it be that evil exists? These questions concern the philosophy of religion.
Epistemology is an area of philosophy that attempts to answer questions such as: What is knowledge? Do we really have any? And how do we tell?
Some philosophers (skeptics) have insisted that we really have no knowledge at all. Some have claimed that we obviously do, and the source of that knowledge is our empirical experience of the world, i.e. what is revealed through sense experience. These philosophers are known as empiricists. Others (rationalists) have thought that sense experience can give us merely opinion, not knowledge. Knowledge—as we have in math and logic—is attainable, but it comes through reason, not sensory experience.
Ethics is a branch of philosophy concerned primarily with value and obligation, and asks such questions as: What actions are morally right? What is good? What sorts of persons should we strive to be? There have been moral skeptics, i.e. those who deny there are any objective moral truths or any such thing as knowledge in ethics. Or perhaps there are moral truths but they are relative to a society's practices and beliefs. So that what is right in one society may be wrong in another. Some moral relativists hold such views. Some philosophers who allow that there can be moral knowledge, claim that the rightness and wrongness of actions are strictly a matter of the value of the action's consequences. But many philosophers think that an action's consequences, while important, are secondary to other factors in determining right and wrong, factors such as whether the action is commanded by God or whether the action is in accordance with certain basic moral principles. And, of course, there is the ever-perplexing question: Why should we be moral?
An important area, closely connected with ethics, is political philosophy. Here the main questions are: What is the nature of the state and the source of its authority? What are its limits? Are there such things as human rights? Should there be a world government?
Logic is mainly an attempt to answer the question: What is correct reasoning? Logic is not so much a separate branch of philosophy as it is, as Aristotle said, a prerequisite to doing any philosophy or, indeed, any inquiry which involves reasoning. Whether we seek truth in metaphysics or in physics, in ethics or in economics, the importance of good reasoning is paramount, and logic, which attempts to spell out the principles of good reasoning, is universally valued.
What is it that philosophers do when they do philosophy? Much could be said here, but at lest two activities come to mind as typical of the methods of philosophers. Philosophers have from earliest times engaged in speculation, and philosophers have, for almost as long, engaged in analysis.
Speculation is merely the use of imagination and logic to offer new possibilities about things, especially about things not yet understood by science. The very first ancient Greek philosophers were speculators about the nature of reality. They wished to make sense of the rich but confusing world of sense experience, and they thought that there must be some underlying principle or principles of reality that could explain it all. Thales (600 B.C.) thought the underlying principle was water. Others had other speculative ideas about reality, some farfetched, but some quite remarkable for their anticipation of later scientific discoveries. Anaximander (550 B.C.) thought that reality, including the planets and life on earth, had evolved from a primal substance infinite and eternal. Perhaps the most rermarkable theory was that of Democritus (450 B.C.) who held that reality consisted of tiny invisible, indivisible particles called atoms. These examples show the connection between science and speculative philosophy: philosophy offers some possibilities which science can not prove or disprove at the time. But as these possibilities received scientific confirmation, what was philosophy ceases to be and becomes part of science. Indeed, much of what is now science was once part of speculative philosophy. Before the birth of modern science in the 17th century, physics was officially known as "natural philosophy." In more recent times what began as philosophical speculation about the nature and origin of the universe has led to the emergence of scientific cosmology and the confirmation of theories like the big bang.
Philosophical speculation has proved useful in non-scientific areas as well. When Thomas Jefferson and the American Founding Fathers undertook the "American experient" they were borrowing heavily on the political philosophers of the previous century, especially John Locke (Treatise on Government, 1690) who provided revolutionary ideas about the virtues of represented government, the separation of powers and human rights, including the right of revolution.
Analysis typically involves the inspection and definition of concepts in order to gain a clearer understanding of things, especially things that the philosopher finds puzzling. Philosophers have perennially asked such questions as What is justice? What is knowledge? What is consciousness? What is reality? And these questions call for analysis of the concepts involved, viz. the concept of justice and the concept of knowledge.
As an example of philosophical analysis (though somewhat simplistic) consider the problem of the tree that falls in the forest with no one (not even a bird or chipmunk) around to hear it. The question to be answered is: Does the falling tree, when it hits the ground, make any sound? You may have heard of this problem. It is sometimes used (wrongly) as an example of a philosophical question that has no answer, or (again wrongly) of the pointlessness of philosophical investigation. But the question does have a definite answer, and the example nicely illustrates (even if overly simplified) the usefulness of philosophical analysis.
On first take, some want to answer that obviously the tree will make a sound. After all, sound is something objectively real which shouldn't need the presence of a perceiver to occur, even if it is true that we've never heard a sound that we didn't hear. Even the sound we didn't hear could be evidenced by (say) a tape recorder placed in the vicinity. So yes, it makes a sound, or so it seems. But, in contrast, it also seems that sound is a subjective phenomenon, something not unlike a sweet taste or the feeling of pain—things that seem to require a perceiver. And so one might well doubt whether the tree really makes any sound. What should be apparent here is that "sound" has more than one meaning. That is, there is more than one concept of sound. Indeed, consider two definitions of sound, one which we might call the physics concept, and the other the psychology concept of sound.
soundphys = vibrations in a medium (such as air)
soundpsy = a sensation; an auditory experience
These are both legitimate definitions. The first (physics) reflects interest in sound as a physical phenomenon. The second (psychology) reflects interest in sound as a kind of experience. Notice that these two kinds of sound, though related, are different and can occur independent of each other. Normally sound as vibrations causes sound as an experience. But they can occur independently, i.e. one without the other. For example, sound as vibrations doesn't have to cause sound as an experience (perceivers might not be present or their ears/brains might be damaged). And sound as an experience could occur without being caused by vibrations in the air (the perceiver might be undergoing some internal hallucinogenic stimulus from chemicals in the brain). Once we see the distinction between these two concepts we can see that the original question is ambiguous; it has more than one meaning. The question (Will the tree make any sound?) is really one of two questions:
(1) Will the tree make any soundphys?
(2) Will the tree make any soundpsy?
The answer to the original question depends on the sort of sound the questioner is asking about. The answer to (1) is: Yes, there will be sound in the physics sense (soundphys i.e. vibrations). The answer to (2) is: No, there will not be sound in the psychology sense (soundpsy i.e. auditory experience). So the question, once clarified, has a definite answer.
This example (though untypically simple) illustrates not only the technique of philosophical analysis, but it also shows its importance. Analysis reminds us that words have more than one meaning, and things called by the same name may really be different concepts. The clarification of concepts is often a prerequisite to a proper understanding of a problem which, in turn, is a prerequisite for dispelling confusion and providing a satisfactory answer to some of philosophy's ultimate questions.