I am not trying to be difficult, but I am not sure philosophy is difficult to define, or at least I suggest it is not any more difficult to define than (for example) the sciences, the humanities, love or works of art, war and peace, and so on. I usually define "philosophy" as having two levels or dimensions. On the one had, and most generally, to have a view of reality and values is to have a philosophy. Given this general definition, every thoughtful person has a philosophy of some kind. Going further, it should be noted that philosophy involves critical reflection on one or more such views, inquiring into meaning and coherence and raising questions of justification (why accept one view rather than another? or why accept any view at all?) This definition (or maybe it should be thought of as a "characterization" or depiction or sketch) can then be enhanced by offering examples and then by noting how philosophy has a host of sub-fields from metaphysics, epistemology, ethical theory or, more broadly axiology, etc, and then by taking note of still further sub-fields such as the philosophy of science, philosophy of religion, philosophy of art, and so on.
Difficulties might emerge, however, insofar as defining philosophy in further detail most likely will have to involve the practice of philosophy. There are controversial philosophical views on the nature and methodologies that are promising in, say, metaphysics.
I must concede that some further difficulties could still emerge, notwithstanding my optimistic opening paragraph. An element of the definition of philosophy I have not mentioned so far is based on the etymology of "philosophy," which comes from the Greek for the love of wisdom. I am inclined to the view that goes back to Socrates and Plato that the life of a philosopher is one that involves (or should involve) practicing the love of wisdom. It is, therefore, a way of life. But there are some philosophers who prefer a more academic or theoretical (or abstracted?) approach to philosophy in which how you live (when you are not in the seminar room or conference) is beside the point. In the later case, someone may claim that one could be an outstanding philosopher (who, let us imagine, comes up with a brilliant philosophy of biology) but who lives a life of cruel indifference to the persons and values around him. In such a situation, perhaps I need to concede that defining "philosophy" is difficult, for I would say of the later (imagined) person that while he is "technically" doing outstanding philosophical work, he is not living his life in light of the love of wisdom and thus his claim to be a philosopher (in the full sense) is tainted.
So, in my reply, I offer a modest challenge to you by providing a (relatively) non-problematic (or not too messy) of a definition of philosophy, but then go on to concede that (interesting) difficulties can well emerge when one looks more closely at the details and boundaries of philosophy. My hope is that persons who grapple with defining philosophy might find themselves drawn into the practice of philosophy itself (a practice in light of my preferred definition) which will involve seeking to live out of the love of wisdom.
The quick answer is that 'analytic' philosophy has not, but 'continental' philosophy has. Almost all the major figures in continental philosophy after Husserl engaged with psychoanalytic thinking - Heidegger, Scheler, Merleau-Ponty, Sartre, Derrida, Foucault, and the French feminist school of Irigaray, Cixous and Kristeva. So continental philosophy as a discipline tends to work with and from an awareness of psychoanalytic thinking, and this has an effect on a very wide range of issues (language, ethics, gender, mind, politics...)
Analytic philosophy has been more sceptical about the truth of the psychoanalytic model of the mind, and engaged far more with cognitive, and more recently social, psychology. It has only begun to deal with the unconscious mind through these empirical theories. There are exceptions; Richard Wollheim and Jonathan Lear have written widely on psychoanalysis, and a number of writers in ethics, e.g. Charles Taylor, Harry Frankfurt, Richard Moran, John Cottingham, David Velleman, and Edward Harcourt have argued for a psychoanalytically informed account of moral psychology and self-knowledge (as have I). But even among those sympathetic to psychoanalysis, the range of issues on which psychoanalytic thought is brought to bear has been relatively limited.
First, philosophy can contribute to world peace by helping us think through the ethical importance of peace -- and of war. Philosophy has a long tradition of inquiry into the conditions for morally justifiable violence. A few philosophers have glorified war. Others have argued that war is justified when war advances a state's interests' ('realists') or when certain conditions are met (just war theory). Other philosophers have advocated for pacifism. Good overviews of these positions are available here:
Second, philosophy can contribute to world peace by undermining the conditions under which war tends to thrive and by pointing to alternative ways to resolve conflicts that might otherwise lead to violence. Starry-eyed though this might sound, philosophical inquiry tends to induce, on the one hand, modesty or humility about one's own beliefs, as well, on the other hand, as a greater appreciation for the merits of others' beliefs. Thus, philosophy can serve to defuse, or at least dampen, conflicts arising from clashing worldviews about ethics, religions, etc. Going along with this, philosophy offers us a non-violent model for resolving our disputes: through reasoned argument. Far better in most every case for us to reach a reasoned consensus that avoids war than to march toward an armed conflict.
Of course, philosophy is no magic pill, world peace-wise. But I'm pretty confident that a healthy dose of philosophy could do a lot to diminish the sad human tendency toward intercommunity violence.
A tough one - I'd be interested to see other panelists weigh in!
The first thing to say is that it's hard to identify any limits to the subject matter of philosophical questions. Traditionally, philosophy has addressed questions about human nature, the nature of reality, knowledge, value, beauty, reason, and so on. But in recent decades, philosophers have turned their attention to an ever-widening circle of topics: medicine, law, the family, race, sports, business, gender, technology, religion the environment, and so on. So it doesn't seem as if the defining characteristic of a philosophical question is what it asks about.
One characteristic of a philosophical question is that it tends to be general. This is not to deny that we are often motivated to ask philosophical questions by very specific concerns. We might be motivated to ask the philosophical question 'what makes a person morally responsible for our actions?' by our interest in whether Charles Manson was responsible for his criminal actions. Or we might be motivated to ask the philosophical question 'what is the nature of causation?' by our interest in what causes cancer. But a philosophical question nearly always addresses a class of phenomenon rather than a single member of that class.
A second feature of many philosophical questions is that progress on them often requires analysis of, or investigation into, the concepts found in the question. 'Does God exist?', for instance, is a question for which we need to have some understanding of what 'God' refers to before we can coherently investigate the question. Suppose someone held up his pet turtle, which he happened to have named 'God', and claimed that he's thereby proven that God exists. This wouldn't be a satisfactory 'proof' of God's existence because the turtle lacks the attributes of 'God' referred to in the question (attributes like having supernatural powers, etc.) Likewise, 'is honesty a virtue?' or 'what is the value of knowledge?' are questions where, if we can answer them at all, we first need to arrive at some understanding of exactly what we're being asked.
Finally, philosophical questions tend to be such that either they cannot be answered by straightforward empirical methods (or it is controversial whether they can be answered by straightforward empirical methods). Logic, for example, is not an empirical science: Conclusions about which kinds of claims are entailed by other kinds of claims are not reached by conducting experiments, making observations, formulating theories, etc. Many moral philosophers would say the same about the fundamental claims of morality. Very often though, philosophical disputes revolve about whether a question can be answered through straightforward empirical means or not. For instance, 'what is the nature of consciousness?' is a philosophical question in part because some philosophers believe it can be answered through empirical investigations (in psychology, neuroscience, etc.), whereas other philosophers deny that it can be answered through those kinds of investigations. But the fact that there's dispute about the applicability of empirical methods in answering this question is a good indicator of the question's being philosophical in nature.
Yes-- all the time. Take for example Robert Nozick's idea of the pleasure machine. Nozick asks - if there were a machine that you could just to be hooked up to that would guarantee that you have an entire life of the highest pleasure - but which would take you out of the hurly burly of everyday existence -- would you want to be hooked up? The vast majority of people say NO - which Nozick takes to prove that most of us believe there is more to happiness than pleasure. But yes, philosophers frequently use fictions/ thought experiments to either make or refute an argument.
I think that the philosophy in the first instance should be learned by engaging with the puzzles that it discusses. It is only after one has got into a sense of the puzzles and how philosophers tackle them that it really makes sense to study the chronology or schools of philosophy. I think this is because at the heart of philosophy is philosophising, doing philosophy rather than studying philosophy. Philosophy is about making sense of ourselves and our situation. To do philosophy is to approach the goal of making sense in a particular way, to engage in a certain kind of practice of enquiry. Philosophical questions aren’t solved by empirical investigation (though that doesn’t mean such investigation is irrelevant), there is a particular emphasis on conceptual clarification, many distinctive marks of philosophizing derive from the enquiries of Socrates, such as an unwillingness to sit with easy or superficial answers, a careful attention to language, the insistent development of a point in both depth and breadth, the giving and challenging of reasons, the uncovering of assumptions, the consideration of counterexamples and implications, and so on.
Philosophy in universities is often described as a “continuing conversation” with the famous dead. (This cannot be exactly right, not least because the cultural significance and context of the views changes.) As in any conversation, we must understand what has been said (history of philosophy) and contribute our thoughts in response. To join a conversation that already exists, to work with the products of an ongoing enquiry, there is much that will need to be learned. And this forms the basis of what university students of philosophy study. But it is central to following the conversation that you understand first what drives it.
So I would recommend a aspiring philosophers start with books that discuss puzzles, rather than books that lay out the development of philosophy through time. I think once you are really into philosophy, and have a good sense of what it is to do philosophy, then the latter kind of book can be very useful. So in the first instance I would recommend, e.g. Stephen Law's The philosophy gym or Julian Baggini's The pig who wants to be eaten. These are more conversational books and so may help with learning how to talk about philosophy with others. Plato's dialogues - and there are many - remain paradigm examples of philosophical discussion; personally, I'd recommend the 'early dialogues' for more balanced conversation in the text, e.g. Crate, Laches, Protagoras, Gorgias. I don't think that there is a special trick to talking philosophy. John Campbell says that philosophy is thinking in slow motion and I agree.
Think about it. Nearly all controversies with an intellectual component are at least partly controversies about what concepts to use. The deepest controversies in nearly all disciplines aren't the substantive ones, where people disagree about some particular theory or fact, they are the conceptual ones in which people disagree about how to talk about the substantive stuff, what concepts to use.
Philosophy has generally been a clearing house for all these conceptual controversies from all the other disciplines, and from life in general (this isn't a definition, it's a stab at an empirical generalization, though admittedly a somewhat idealized one, in which I leave out a lot of stuff others might like to include within "philosophy"). Philosophical responses to these controversies have been all over the map. Sometimes philosophers just pick up those same controversies and carry on just as the physicists or lawyers or whoever might have done, in the same terms as the physicists or lawyers. Other times they try to formalize or restate other people's controversies, in the process often making them unrecognizable to their home disciplines. Other times they try to generalize among controversies from different fields, or point out analogies or contrasts. In some famous cases, philosophers get constructive themselves, and build systems in which the controversies from other fields can be solved or at least understood within a larger context. Sometimes philosophers skeptically dissolve other people's controversies, or claim to, or point out inconsistencies in other people's claims. Many philosophers have done several of these things on different occasions, or even at the same time.
So when anyone claims that philosophy is (or should be) this or that, they're (at least) claiming that one of these many responses is better or more important than the others, i.e. they're advancing a normative meta-philosophical claim, usually with arguments of some kind or another. Others seek to refute those arguments and make different meta-philosophical claims. To many philosophers these meta-philosophical issues will seem more fundamental and more important than the conceptual controversies from other fields, since it looks to them as if you can't start to address those other controversies until you've settled how to go about it, i.e. what (meta-)concepts to use. Two results: meta-philosophical controversies are even more controversial, even less likely to be settled, than substantive ones from other fields; and second, a huge proportion of philosophical writing is taken up with what looks from the outside like pointless and highly abstract wrangling about what the field is even supposed to be. But as you can see, these results are inevitable in philosophy.
Some people approach this question from the viewpoint of the Greek origins of western philosophy, and the etymology of its name, pointing out that the current collection of highly specialized and abstract squabbles no longer serves the original Greek (or medieval, or early modern) purpose of providing an orientation to thinking in general (Kant's "sich im Denken orientieren"). This purpose has now passed to literature, some say, with Goethe or Proust or Dostoevsky providing better orientations than Wittgenstein or Heidegger or Quine, who are all much harder for the uninitiated to understand.
I have some sympathy with this criticism but I think that if we want philosophy, or some part of philosophy (some appropriate user interface, perhaps) to provide a better orientation to thinking in general, it's important to understand why philosophy has become the way it is; it's inherently, structurally controversial -- especially about its own basic nature and categories -- and can't be any other way.
So the answer to the question is, and has to be, "no," but that isn't a cause for despair, it's simply a recognition that the very nature of what it has been attempting to do, since antiquity, makes any definition of philosophy irrelevant.
If by "assume," you mean "accept without argument," then the answer is yes to the first part of your question and no to the second.
Yes: philosophers assume all sorts of things. They usually assume that there is a world out there and that there are people who at least potentially can read and respond to their arguments. They very often take for granted all sorts of facts, scientific and garden-variety: that there are trees; that people sometimes do things deliberately; that water is made of H2O; that the 4-color conjecture has been successfully proven.
No: this isn't contrary to the intent of philosophy. Except on very eccentric views, philosophy is not the enterprise of doubting everything that can be doubted and accepting only what can be proved from indubitable premises. That may have been Descartes' project, but it's been almost no one else's. In fact, most philosophers would say that this project is deeply flawed.
Philosophy, like the Odyssey begins in the middle of things. Want to think about free will? Start by assuming that there are beings who have intentions and sometimes behave accordingly. Want to think about linguistic meaning? Start by assuming that there are languages and people who use them to communicate. Want to think about cause and effect? Start by assuming that things happen (there are "events," on one way or putting it) and that sometimes what happens fits certain sorts of patterns. And so on.
But in any case, there's no one thing that is the "intent" of philosophy. True: philosophy is relatively non-empirical; we don't generally do experiments to settle philosophical questions. It's hard to see how experiments would tell us what it amounts to for one thing to cause another, for example. But sometimes empirical findings are relevant to philosophical thinking. For example: what experimental psychology tells us about how we actually make decisions might very well be relevant to how we should think about free will.
Who decides what gets doubted and what gets taken for granted? The philosopher, and she does it depending on the questions she wants to explore and the state of the broader discussion of those questions. All of this may seem distressingly impure to outsiders, but philosophers would say that it makes it possible to have productive discussions that someone might have a reason to care about.
A not-really-relevant aside: most philosophers don't own philosophical dictionaries, but let that pass.
Here's a non-philosophical word: unicorn. It's easy to explain what it means, but there aren't any real-life examples. Whether a term can be clearly explained and whether there are actual examples are quite different questions.
If it's controversial whether something exists then a philosopher shouldn't pretend otherwise, but the question of whether something exists (God, for instance) might be an interesting one. And sometimes the best way to understand a notion is a philosophical question. The notion of free will is like that. In that case, there's no one meaning for the term, but it's possible to have a perfectly reasonable discussion of what might count as free will and why some answers might be better than others. In fact that sort of discussion comes up in many disciplines. Philosophers are unusual in that they're trained to notice this kind of unclarity and to reason about it carefully.