Philosophy is the study of underlying things. This means philosophy tries to understand the reasons or basis for things. It also tries to understand how things should be. "" is the Ancient Greek word for the "love of wisdom". A person who does philosophy is called a philosopher. A philosopher is a kind of thinker or researcher. A "philosophy" can also mean a group of ideas by philosophers, or by a philosopher. Philosophy is a way of thinking about the world, the universe, and society. In the past, sciences were part of philosophy as well.

Ideas
The ideas in philosophy are often general and abstract. But this does not mean that philosophy is not about the real world. Ethics, for example, asks about how to be good in our day-to-day lives. Metaphysics asks about how the world works and what it is made of.
Sometimes people talk about how they have a ‘personal philosophy’, which means the way a person thinks about the world. This article is not about people's ’personal philosophies’. This article is about the ideas that have been discussed by philosophers (people who think and write about ways of thinking) for a long time.

Questions
One philosophical question is this: "Is there any knowledge in the world which is so certain that no reasonable man could doubt it?". Other questions asked by philosophers are these:

 what should we do in our lives?
 What happens to a soul after death, how does a soul enter into the body before death?
Why are we born?
Why should we live?
Why are there so many hurdles in life?
How do we overcome suffering?
What is the importance of the material life?
Will the universe exist forever?
 What is beauty?
 Do we have free will?
 Does God exist?
 Does the world around us exist?
 What is truth? 
 What is evil?
 What is the relationship between mind and body?
 What is the meaning of life?

History 
The etymological meaning of the word 'Philosophy' is 'love of wisdom'. It comes from the Greek word 'Philosophia', with 'Philo' meaning 'beloved' and 'Sophia' meaning 'wisdom.

There are different types of philosophy from different times and places. Some philosophers came from Ancient Greece, such as Plato and Aristotle. Others came from Asia, such as Confucius or Buddha, or Adi  Shankara and Laozi. Some philosophers are from the Middle Ages in Europe, such as William of Ockham or Saint Thomas Aquinas.

Philosophers from the 1600s, 1700s, and 1800s included Thomas Hobbes, René Descartes, John Locke, David Hume, and Immanuel Kant. Philosophers from the 1900s included Søren Kierkegaard, Ludwig Wittgenstein, and Jean-Paul Sartre.

 Areas of inquiry Philosophy is the study of humans and the world by thinking and asking questions. It is a science and an art. Philosophy tries to answer important questions by coming up with answers about real things and asking "why?"

Sometimes, philosophy tries to answer the same questions as religion and science. Philosophers do not all give the same answers to a question. Many types of philosophy criticize or even attack the beliefs of science and religion.

In his work Critique of Pure Reason,  Immanuel Kant asked the following questions:
What can I say? 
What shall I do?
What dare I hope?
What is man?
The answers to these questions gives the different domains or categories of philosophy.

 Categories in philosophy 
Philosophy can be divided into different groups, based on the types of questions that it asks. Below is a list of questions split into groups. One possible list of answers to these questions can be called a 'philosophy'. There are many different 'philosophies', because all of these questions have many different answers according to different people. Not all philosophies ask the same questions. These are the questions that are usually asked by philosophers from the Western world:Metaphysics:

Metaphysics is sometimes split up into ontology (the philosophy of real life and living things), the philosophy of mind and the philosophy of religion; but these sub-branches are very close together.

Ontology:
 What is the world that we see around us? (What is reality?)
 Is there more to the world than just what we see or hear? 
 If nobody sees something happening, does that mean that it did not happen?
 What does it mean to say that something is possible? Do other worlds exist?
 Is there anything very special about being a human being or being alive at all?
 If not, why do some people think that there is?
 What is space? What is time?

The philosophy of mind:
 What is a mind?
 What is a body?
 What is consciousness?
 Do people make choices, or can they only choose to do one thing? (Do people have free will?)
 What makes words or ideas meaningful? (What is the relation between meaningful words or ideas and the things that they mean?)

The philosophy of religion:
 Do people have souls?
 Is there a God who created the Universe?In epistemology:

 What is knowledge? 
 How can we know anything?
 What is science?
 What is truth?In ethics:
 What are right and wrong, good and bad?
 Should people do some things and not others?
 What is justice?In aesthetics:
 What is beauty? What if one person thinks a painting is beautiful, but another person thinks the painting is ugly? Can the painting be beautiful and ugly at the same time?
 Are true things beautiful?
 Are good things beautiful?
 What is art? We commonly think that a sculpture in a museum is art. If a sculptor sculpts a sculpture of a rock from clay, and puts it in a museum, many would call it art. But what if a person picks up a rock from the ground - is the rock a piece of art?In logic:
 What do the words we use mean?
 How can we say things (especially ideas) in a way that only has one meaning?
 Can all ideas be expressed using language?
 How does the truth of an argument's premise affect the truth of its conclusion?
 How can we reason correctly?In axiology''':
 What has value?
 Is time really money? or have we made it so?
 Does love, beauty, or justice hold any value?

Other divisions include eschatology, teleology and theology. In past centuries natural science was included in philosophy, and called "natural philosophy".

 Is philosophy good or bad? 
Does philosophy do any good? Very few people would dispute this. It is easy to argue that philosophy is a good thing, because it helps people to think more clearly. Philosophy helps people to understand the world and the way people act and think. Philosophers believe that asking philosophical questions is useful because it brings wisdom and helps people to learn about the world and each other. Some philosophers might even argue that the question "Is philosophy good or bad?" is a philosophical question itself.

However, some people think that philosophy is harmful, as philosophy encourages free-thinking and often questions the beliefs that others hold. For example, philosophies such as some existentialist views say that there is no meaning to life or human existence, except the meaning that we make up or invent. People from some religions do not agree with the beliefs of existentialism.

Every major science, including physics, biology, and chemistry, are disciplines that were once considered as philosophy. Medicine was always considered a practical art, however. As facts about nature became more understood, these subjects branched away. Psychology only split a century and a half ago. In our own time, subjects such as consciousness studies, decision theory, and applied ethics have increasingly found independence from philosophy as a whole. Because of this, philosophy seems useful because it spins off new kinds of science.

 What philosophers do 
Philosophers ask questions about ideas (concepts). They try to find answers to those questions. Some thinkers find it very hard to find those words that best describe the ideas they have. When they find answers to some of these questions philosophers often have the same problem, that is how to best tell the answers they found to other people. Depending on the meaning of the words they use, the answers change.

Some philosophers are full-time thinkers (called academics), who work for universities or colleges. These philosophers write books and articles about philosophy and teach classes about philosophy to university or college students.

Other philosophers are just "hobby" thinkers who think about philosophy during their free time. A small number of hobby thinkers have thought so much about philosophy that they are able to write articles for philosophy magazines. Other people approach philosophy from another job. For example, monks, artists, and scientists may think about philosophical ideas and questions.

Most philosophers work by asking questions and looking for good definitions (meanings) of words to help them understand what a question means.

Some philosophers say the only thing needed to answer a question is to find out what it means. The only thing that makes philosophical questions (such as those above) difficult is that people do not really know what they mean. Ludwig Wittgenstein believed this.

Philosophers often use both real and imaginary examples to make a point. For example, they may write about a real or fictional person in order to show what they think a good person or a bad person is like.

Some philosophers look for the simplest way to answer a question and say that is probably the right answer. This is a process called Occam's razor. Others believe that complicated answers to questions can also be right. For an example of a philosophical problem, see the God paradox.

Philosophers use logic to solve problems and answer questions. Logical consistency is a cornerstone of any acceptable theory. Philosophers who disagree with a theory will often try to find a logical contradiction in a theory. If they find a contradiction, this gives them a reason to reject that theory. If they do not find an inconsistency, the philosopher might show that the theory leads to a conclusion which is either unacceptable or ridiculous. This second approach is usually called reductio ad absurdum.

 Some philosophers 
People listed here should be genuine philosophers, rather than social or political campaigners. The lists are not meant to be complete.

 The ancient Greek philosophers 

 Heraclitus
Socrates
Plato

Aristotle

Epicurus
Diogenes

 Later European/Western philosophers 
 Saint Augustine
 Saint Thomas Aquinas
 Duns Scotus
 Bonaventure
 William of Ockham
 George Berkeley
 Auguste Comte
 René Descartes
 Ralph Waldo Emerson
 Georg Wilhelm Frederich Hegel
 Thomas Hobbes
 David Hume
 Immanuel Kant
 Søren Kierkegaard
 Gottfried Wilhelm Leibniz
 John Locke
 Niccolò Machiavelli
 John Stuart Mill
 Jean-Jacques Rousseau
 Arthur Schopenhauer
 Baruch Spinoza
 William Whewell
 Friedrich Nietzsche

 Modern European and American philosophers 
 Louis Althusser
 G. E. M. Anscombe
 Simone de Beauvoir
 David Chalmers
John Dewey
Christian DeQuincey
 Martin Heidegger
 Karl Popper
 John Rawls
 Bertrand Russell
 Jean-Paul Sartre
 Ludwig Wittgenstein
 Albert Camus

 Latin American and Latina/o philosophers 

 Gloria E. Anzaldúa 
 Giannina Braschi 
 Sor Juana Inez de la Cruz 
 Maria Lugones 
 Ofelia Schutte
Eugenio María de Hostos

 Asian/Eastern philosophers 
 Avicenna
 Osho
 Confucius
 Siddhārta Gautama (the Gautama Buddha)
 Omar Khayyám
 Nanak
 Chuang Tzu
 Lao Tzu
 Sohrevardi
 Allama Iqbal

Related pages
Fallacy
Truth

 General sources 

 Blumenau, Ralph. Philosophy and living. 
 Craig, Edward. Philosophy: a very short introduction. 
 Harrison-Barbet, Anthony. Mastering philosophy. 
 Russell, Bertrand. The problems of philosophy. 
 Sinclair, Alistair J.  2008. What is philosophy? An introduction. 
 Sober, Elliott 2001. Core questions in philosophy: a text with readings. Upper Saddle River, Prentice Hall. 
 Solomon, Robert C. Big questions: a short introduction to philosophy. 
 Warburton, Nigel. Philosophy: the basics. 
 Nagel, Thomas. What does it all mean? A very short introduction to philosophy. 
  Pojman, Louis P.  Classics of Philosophy (vols. 1, 2, & 3) 
 Arthur, Edwin  The English Philosophers from Bacon to Mill 
 Beardsley, Monroe  European Philosophers from Descartes to Nietzsche 
 Cottingham, John 2008. Western philosophy: an anthology. 2nd ed. Malden, MA: Blackwell Pub., . 
 Tarnas, Richard. The passion of the Western mind: understanding the ideas that have shaped our world view''.

References

Other websites
The School of Life on YouTube
Einzelgänger (In search of) on YouTube

Philosophy
Humanities