One of the oldest aspirations of philosophy has been to inquire into the ultimate nature of reality. The phrase sounds impressive enough, but what does it mean? Nowadays most people would say that investigating what there is, or what the world is like, is the job of the scientist, not the philosopher. But in earlier times the two roles were not clearly separated. When the writers of the Middle Ages described Aristotle as a philosopher (indeed he was known as The Philosopher), they were thinking partly of his accounts of the natural world, his physics, biology and so on.
The fact is that almost anyone who studies philosophy will sooner or late encounter disparaging remarks about the subject, such as that it is just hair-splitting and irrelevant - a subject best pursued by those who want to live in an ivory tower. However, Bertrand Russell (1872-1970) responds to such remarks with an aggressive defense of the value of philosophy. He argues that Philosophy has value not because it is likely to provide definitive answers to the questions it asks, but rather because the questions themselves are profound and important ones. Philosophical contemplation removes us from our narrow everyday concerns and takes us to a realm of generality, which can put our lives into a new perspective. Interestingly, Russell writes, "If you ask a mathematician, a mineralogist, a historian, or any other man of learning what definite body of truths has been ascertained by his science, his answer will last as long as you are willing to listen. But if you put the same question to a philosopher, he will, if he is candid, have to confess that his study has not achieved positive results such as have been achieved by other sciences. It is true that this is partly accounted for by the fact that, as soon as definite knowledge concerning any subject becomes possible, this subject ceases to be called 'philosophy', and becomes a separate science. The whole study of the heavens, which now belongs to astronomy, was once included in philosophy; Newton's great work was called 'the mathematical principles of natural philosophy'. Similarly, the study of the human mind, which a part of philosophy, has now been separated from philosophy and has become the science of psychology." He concludes, "Thus to a great extent, the uncertainty of philosophy is more apparent than real: those questions which are already capable of definite answers are placed in the sciences, while those only to which, at present, no definite answer can be given, remain to form the residue which is called philosophy." (From Russell, "The Value of Philosophy" cited in Philosophy: Basic Readings", ed. Nigel Warburton (London: The Rutledge Group, 2004), 24-28.)]
But Aristotle also aimed to investigate the nature of being qua being, or being as such; he wanted to analyze the basic notions that are involved in our understanding of the world. The book in which he presents this idea of a general study of being is called the Metaphysics. The history of metaphysics is the history of various fundamental theories about "ontology" or "being". The paragraphs that follow, while not exhaustive of metaphysical speculation, reflect certain key concepts, ideas, and developmental direction of metaphysical of certain of the leading Philosophers.
