Nowadays, the search for ‘wisdom’ has become fragmented. Science now takes care of enquiries into natural phenomena, and ethics and morality (though still sometimes described as ‘philosophy’) belong not only to philosophy, but also to such disciplines as politics, psychology, sociology and theology (see below). Philosophy—at least academic philosophy—is a disinterested endeavour to examine human reasoning itself, to take abstract questions and consider their validity not as specific truths but as forms of theory or explanation. The only similarity between this activity and ancient philosophy is that it requires constant back-reference to past ideas and past intellectual precedents. Philosophy is an academic study taught by means of its own history; it is a subject which grows by accretion, the new constantly building on and modifying the old.

One of the main tools of philosophy is logic, and a separate branch of the discipline deals with this alone. Logic is the consideration of argument: not of whether an argument is subjectively valid, but whether it is objectively so. Logic removes partiality from the consideration of argument, reducing it to a kind of framework which has consistency and rigour. It is concerned with the structures and principles of reasoning, with the succession and interdependence of intellectual statements. It is related to mathematical logic, in which symbols replace verbal statements; it leads to and facilitates the whole vast area of linguistic philosophy, in which the edifice of meaning and purpose in the use of words is rigorously examined.

Another central concern of philosophy is the nature of reality, and our perception of it. What do we know, how do we know it and are there limits to our knowledge? Investigating these matters is perhaps the overarching agenda of all philosophy, and has been so from earliest times. In the ancient past, throughout the world, the highest branch of such study was metaphysics: investigation of the ultimate nature of reality, of such things as the existence of the supernatural, the nature of time, or the relationship between mind and body. In 17th-century Europe, beginning with the work of Descartes, metaphysics gradually gave way to epistemology, the investigation of knowledge itself. (Descartes, for example, starting from the famous premise Cogito, ergo sum, ‘I think; therefore I am’, sought to produce a universal system for all human knowledge; Spinoza, Locke, Hume and others examined such matters as where knowledge comes from and what, if any, are the limits of human understanding; modern epistemologists devote themselves to questions of the testing and validation of knowledge, and of its relationship to thought and meaning.)

From earliest times, philosophy has shared two preoccupations with such other disciplines as (what we would now call) politics, psychology and theology. First is the nature of identity. What is personal identity? Is it a material or an immaterial thing? Does it reside in the mind or the body, or in both? Do mind and soul exist, and if so, what are they? Second is our relationship with the world outside ourselves, with the supernatural (if it exists) and with other people. Are morals and ethics—not to mention such things as benefit and harm, duty, good and bad, right and wrong—abstract entities, or human constructs? Are their imperatives innate or learned? It is here, perhaps, that the clear stream of philosophy is most muddied by ‘outside’ considerations. We all have notions of how we, and others, should behave, of the correlatives (such as the supernatural or the force of law) which affect behaviour, and of the moral and ethical status quo. For some people, a ‘philosophy of life’ is the totality of such notions which governs their approach to everyday living. Some academic philosophers have devoted themselves to such matters. But by and large, academic philosophy has treated them in the same way as all its other concerns: that is, it has attempted to remove the personal from consideration and to discuss each argument in the abstract. KMcL