Introduction ''Philosophy: The love, study, or pursuit of wisdom, truth, or knowledge.'' OXFORD ENGLISH DICTIONARY (2020) ''Philosophy, if it cannot answer so many questions as we could wish, has at least the power of asking questions which increase the interest of the world, and show the strangeness and wonder lying just below the surface even in the commonest things of daily life.'' BERTRAND RUSSELL, THE PROBLEMS OF PHILOSOPHY (1912) The Oxford English Dictionary has no fewer than nine major definitions of what philosophy is. If nothing else, that fact highlights just how vast and complex the discipline is. What, for example, marks out a philosopher from any other person with a stream of ideas flowing around their head? Would you rather fight a lion or a shark? It''s one of those questions that people sometimes like to pose, knowing that there is neither a ''right'' nor ''wrong'' answer. Usually, it is asked with little more intention than to fill the time, or perhaps to show off some specialist knowledge about the fighting capabilities of one species over the other. Maybe there''ll be the chance to explore some pop culture references - why, say, Jaws is an infinitely more unsettling film than The Lion King . More often than not, there is no great desire to reach some new truth or wisdom.

Yet what if you take the question seriously: ruminating on one''s own mortality, the role of humanity within the natural order, why man might feel the need to test himself against other species, or what might be regarded as a fair and just result, or indeed whether the contest would even be a material reality? You might end up with some serious insights into yourself and the world around you. Then, dear reader, you might start to consider yourself a philosopher. In certain respects, it is easier to say what philosophy is not. It is not ''art'', in which one''s imagination is allowed to run its course free from the restraints of having to justify itself on any basis other than how pleasing the results are. It is not ''science'', since although a philosophical thesis needs to be rooted in some sort of rational basis, it is held to a different level of ''proof'' than science generally demands. Nor is it ''religion'', for religions customarily expect a level of inherent faith beyond that which we are prepared to allow philosophy. Yet philosophy overlaps with art, science and religion. They are, after all, fields united in a desire to make sense of the world.

We all, to some degree, deal in philosophy every day. Even an act as commonplace as how we cross the road reflects an attitude to life. Do you step out without looking, or wait for a stream of traffic expressly to dart in between the vehicles, or are you cautious, waiting for the green man to flash even when you can see the road is clear? Each method speaks of an attitude to life, to risk, to what we deem to be important and reasonable, and perhaps even reveals what we think about death and God. We are all, then, a little bit philosopher. It is just that the professional (as it were) philosopher spends more time consciously contemplating life in search of greater knowledge and wisdom. It is a slow process, too. If we date the formal discipline of philosophy back to ancient Greece 2,500 or more years ago, we remain pilgrims on the pathway, the goals of complete knowledge and wisdom still far over the horizon (if they are there at all). But, as Bertrand Russell''s quotation above suggests, the path travelled is really rather more important than the destination being reached.

(In his mischievous Devil''s Dictionary of 1911, Ambrose Bierce defined philosophy as ''A route of many roads leading from nowhere to nothing.'') Although we may not arrive at all the right answers, what we learn from the process of investigation is valuable in itself. As this book illustrates, philosophy is notable less for its consensus than for the divergence of opinions. Some of the greatest thinkers in the history of the field had utterly opposing views. (William James, a key figure in philosophical pragmatism, said: ''There is only one thing a philosopher can be relied upon to do, and that is to contradict other philosophers.'') Yet each of their outlooks makes an utterly valid contribution to increasing human understanding. The idea, though, that we can train ourselves up to think as an ideal, composite philosopher is wrong-headed. Instead, this volume aims to do three things: Explore ways in which the philosopher approaches the quandary of how best to expand knowledge and wisdom.

Investigate some of the contrasting intellectual strategies adopted. Drill down into specific theories that have, over millennia, influenced philosophy''s progress. In order to facilitate the navigation of this monumental subject, I have divided the book into three broad areas: Metaphysics (the nature of existence), Epistemology (the study of the nature of knowledge itself) and Ethics (what it is to behave morally). Clearly, no single volume could begin to provide anything approaching a comprehensive overview of all philosophy. Instead, I hope this one will give you a broad-brushstroke impression of many of the issues that a philosopher must keep in mind, as well as several of the most important strands of thought. Along the way, we will encounter a wide and varied assortment of some of the most celebrated philosophers to have ever lived and take a peep at a few of the ideas that have inspired, intrigued and sometimes even confounded them. (As G. W.

F. Hegel is apocryphally said to have observed: ''Only one man ever understood me, and he didn''t understand me.'') We shall also explore great schools of philosophical thought, from idealism and materialism to epicureanism and absurdism. Yes, best prepare now for a lot of ''-isms''! To become a philosopher is not about passing exams, or even about being able to talk the hind legs off your friends and acquaintances as to whether, say, we are all figments of a giant''s dream or else living on the back of a cosmic turtle. It is about a desire to understand more than we already do, aware that we might actually end up feeling like we understand less. It is a long road and the progress is incremental. The great twentieth-century philosopher Ludwig Wittgenstein summed up the struggle neatly: ''Philosophy is like trying to open a safe with a combination lock: each little adjustment of the dials seems to achieve nothing, only when everything is in place does the door open.'' The word philosophy is derived from the ancient Greek for the ''love of wisdom''.

That seems appropriate. It is something to be embraced, undertaken with love. And when the love affair gets a little bumpy and you wonder whether philosophy is the one for you after all, stick with it, show some patience and kindness, and you''ll likely find that what you put into the relationship is paid back with interest. Sometimes philosophy can be arduous, frustrating and disappointing, but in the end it is magnificent. In the words of Henri de Saint-Simon''s Mémoire sur la science de l''homme (''Essay on the Science of Man'', 1813): The philosopher places himself at the summit of thought; from there he views what the world has been and what it must become. He is not just an observer, he is an actor; he is an actor of the highest kind. A NOTE: WHERE ARE ALL THE WOMEN? ''There must be more equality established in society, or morality will never gain ground, and this virtuous equality will not rest firmly even when founded on a rock, if one half of mankind be chained to its bottom by fate, for they will be continually undermining it through ignorance or pride.'' MARY WOLLSTONECRAFT, VINDICATION OF THE RIGHTS OF WOMEN (1792) Before embarking on our journey, there is a philosophical elephant in the room that needs to be discussed.

So, let''s do it now. This book attempts to fit a lot into a manageable number of pages. It strives to encapsulate a good deal of philosophical thought that was established over two and a half millennia. It is ''Philosophy''s Greatest Hits'', if you like (and apologies if your favourite track has not made it onto the final listing). In doing so, however, something is inescapable: the vast majority of the voices who have reverberated over this lengthy timescale belong to men. It too often feels as if philosophy is a boys'' club. To a large extent, it has been. For much of history, women were excluded from those academic and social institutions that governed the discipline and decided whose voices would be heard.

This is undoubtedly philosophy''s loss. Had more women been encouraged to bring their experiences of the world, how much richer the philosophical landscape would be. Instead, philosophy has mostly been filtered by a single sex that, by and large, has made little effort to understand how a world view may alter when viewed through the prism of womanhood, with its distinct social, biological and psychological features. Remarkably, given the barriers to entry, a few women broke through, even in ancient times. Among the notable exceptions are Maitreyi, the eight-century BC Indian philosopher; Hipparchia of Maroneia, a Cynic philosopher of the fourth century BC; and her close contemporary, Arete of Cyrene, who reputedly succeeded her father to lead the School of Cyrene. Then there is Hypatia, who lived in fourth- and fifth-century AD Egypt, a celebrated polymath and exponent of Neoplatonic thought who, tellingly, was murdered by a mob amid a climate of interreligious conflict. ''Reserve your right to t.