For some people the answer that springs to mind is, "Philosophy is how I approach life, the way I deal with things and events in my life." They may mean that they are "easy going" or that they are "serious" or they may mean nothing particular at all -- just what they feel is appropriate to the moment. This personal definition is appropriate to the overall personal approach to life so prevalent today. It seems that the idea that anything can have meaning outside of a personal reference -- what it means to me -- has become irrelevant. This is a recent development in human thinking.
Which leads us to a second answer to our question. If we adopt as our personal philosophy a particular system of values, beliefs and principles shared by a group or rationalized by a particular thinker then we have stepped outside of a purely personal approach to thinking and doing. Most personal philosophies admit some effect of systems of values, beliefs and principles that we learned about while growing up or while adults or that formed the context of our formative or adult years. The American social system is steeped in values, beliefs and principles of the Judeo-Christian tradition and effects all of us. But more importantly some of us choose to be Buddhists or Socialists or Stoics -- and in so doing we raise ourselves above the herd and seek to adhere to a system of thought.
With the idea of a system of thought comes another common definition of Philosophy -- namely that it is those ideas related to a particular subject. We can recognize a philosophy of religion and a philosophy of science and a philosophy of education. Subject oriented philosophy may figure large in our professional training or the institutions we use as members of society. But while they may encapsulate the essence of a field they do not address anything beyond that limited scope. They might provide the rationale and means of accomplishing a task but they do not speak to anything beyond.
All of these definitions of philosophy miss the point in one way or another -- mostly by being too particular -- telling us too much and in so doing limiting us too much. The scope of Philosophy is the broadest of any human endeavor. As the online Cambridge Dictionary defines it Philosophy is "the use of reason in understanding such things as the nature of reality and existence, the use and limits of knowledge and the principles that govern and influence moral judgment." In our personal philosophies we might think a little about "the principles that govern and influence moral judgment" but for most of us "the nature of reality and existence" is something we take for granted. Yet for others this is both the most interesting and exciting as well as fundamental question. It is the one that lifts us above our daily existence and the tyranny of the routine and the personal.
In Sophie's World: A Novel About the History of Philosophy (Farrar Straus & Giroux, 1994) Jostein Gaarder has Sophie's mysterious teacher begin her introduction to philosophy with two questions: "Who are you?" and "Where does the world come from?" There seems to be something in human beings that causes us to ask and think about such deep questions. Michael Schermer suggests in How We Believe: The Search for God in an Age of Science (W H Freeman & Co, 1999) that we are genetically (actually epigenetically) programmed to speculate in this way and such thinking began before recorded history and is somehow evolutionarily adaptive. How we react to the deep questions -- whether we approach with curiosity and reason or flee in denial and rationalization -- determines who we are.
The first answers humans developed to their deep questions were myths -- stories of gods and powers that made and ruled their world. The ancient Greeks are the first recorded to have applied reason to the same questions, looking beyond ad hoc explanations of capricious gods to an underlying natural order. Philosophy was born. In ancient times the subject of philosophy was as broad as it was deep, encompassing all of the natural world. As science and mathematics advanced they removed some of the questions we ask about the natural world from the realm that could only be explored by the mind. But they left us with new, interesting questions such as, "What is science?", "What is mathematics?" and "Why do they work?"
Human beings have been reportedly seeking answers to these questions now for 3,000 odd years. And also answering them. This is the History of Philosophy -- the record of what has been said in answer to the same questions we ask today. It is an instructive history with many twists and turns, errors and corrections. It is worth reading and knowing because a truth is a truth and an error is an error today as yesterday. Nevertheless do not be confused: The History of Philosophy is not Philosophy. Philosophy is how we answer these age-old questions for ourselves. History is what others have done before us.
I have said that Philosophy is a human endeavor motivated by a deep questioning. There are several examples of such deep questions but they all reduce to one: "Why?" It is a question that any parent will recognize. Some may dread it while others rejoice when a child asks it. Your personal reaction may say a lot about whether you are a philosopher or not.
Once we become chronological adults some of us fall into thinking we should know the answers. Or we become confused because our children do look to us for answers and we feel we owe them an answer. If we do happen to know something we tend to think that's all there is to it. Having an answer we become supremely confident that at least we know that one thing though in fact we may remain vastly ignorant of many other things. In the comfort of knowing we avoid the insecurity of not knowing and the possibility of never knowing.
However the fundamental characteristic of humanity expressed in philosophy is not answering but questioning.
Being a philosopher is nothing at all like most imagine it to be. It is not an adult preoccupation with answers but a child-like occupation with questions. It is always wondering, always asking "Why?". Being a philosopher is being able to shed the security of knowing in the way adults know and knowing as a child does -- with the wonder and excitement that accompanies knowing something for the the first time.