Philosophy begins with questions.
Some seem surprisingly simple. What is real? How do I know anything? Do I really choose what I do? What makes something right or wrong? What makes a life worth living?
But once we start thinking seriously about them, simple answers become difficult.
For thousands of years, philosophers have explored these questions without reaching conclusions that everyone accepts. Science has answered many questions about how the universe works, but some of the deepest questions about existence, consciousness, knowledge, morality and meaning remain open.
You do not need to study philosophy to think about them. In fact, you probably already do.
Here are ten of the biggest.
What Is Reality?
Look around you. There seems to be an obvious answer: reality is the physical world you can see, hear and touch.
But how do you know that your experience accurately represents the world outside your mind?
Colour provides a simple example. We experience a ripe tomato as red, but redness is not simply sitting on its surface. Light reaches our eyes and our brain produces the experience we call red. Other animals experience the same physical world differently.
So how much of the world we experience belongs to reality itself, and how much is constructed by our minds?
Philosophers have proposed radically different answers. Some believe reality is fundamentally physical. Others have argued that mind or consciousness is more fundamental. Plato even suggested that the changing world we experience is not reality in its deepest form.
Modern physics has added further surprises. At very small scales, matter behaves in ways that bear little resemblance to the solid everyday world around us.
Reality may be considerably stranger than it appears.
[Explore: What Is Reality?]
What Is the Relationship Between Mind and Body?
Your body appears to be physical. Your brain consists of cells, chemicals and electrical activity.
Yet you also have thoughts, memories, emotions and experiences.
How are the two connected?
René Descartes famously argued that mind and matter are fundamentally different things. This became known as dualism.
Most neuroscientists today instead investigate the mind through the workings of the brain. Damage a particular part of the brain and memory, personality, perception or behaviour can change.
But this creates another puzzle.
Even if we eventually understand every process occurring inside the brain, will that explain why those processes are accompanied by an inner experience at all?
Understanding the relationship between brain, mind and experience remains one of the great meeting points between philosophy and neuroscience.
[Explore: The Mind–Body Problem]
What Can We Know?
How do you know what you think you know?
Some knowledge seems to come from our senses. Other knowledge appears to come from reasoning. Much of what we believe comes from other people.
But senses can deceive us. Reasoning can go wrong. Memories change. Authorities can be mistaken.
Descartes pushed this problem to an extreme. What, he wondered, could he know with absolute certainty?
His search eventually produced one of philosophy’s most famous conclusions: if he was thinking, then at least something doing the thinking must exist — “I think, therefore I am.”
Few of us demand absolute certainty before believing anything. Nevertheless, the question remains enormously important.
What counts as good evidence? When is a belief justified? And how certain should we be about the things we think we know?
The branch of philosophy concerned with these questions is called epistemology.
[Explore: What Can We Know?]
Do We Have Free Will?
Imagine you are choosing between tea and coffee.
It feels as though either choice is genuinely available to you.
But your decision arises from a brain shaped by your genes, upbringing, memories, personality and everything that has happened to you before that moment.
Could you really have chosen differently?
If every event has causes, perhaps our decisions are simply another part of that chain. This is the problem of determinism.
Others argue that having causes does not necessarily make an action unfree. You may still be acting freely when your decision reflects your own desires, reasoning and character rather than external coercion.
The question matters far beyond philosophy.
If people are not ultimately responsible for the causes that made them who they are, what does that mean for praise, blame, punishment and personal responsibility?
[Explore: Do We Have Free Will?]
What Is Consciousness?
Consciousness is simultaneously one of the most familiar and mysterious things we know.
You do not merely process information. There is something it feels like to be you.
You experience the colour blue, the taste of coffee, pain, music, memories and thoughts. Somehow physical activity in the brain is associated with this private inner world.
Neuroscience is increasingly able to identify brain processes associated with conscious experience. But a philosophical mystery remains.
Why should any physical process feel like anything from the inside?
Could an extremely sophisticated computer become conscious? Are other animals conscious in ways similar to us? Could consciousness eventually be explained entirely by neuroscience, or are we missing something fundamental about its nature?
We possess consciousness every waking moment while still struggling to explain what it actually is.
[Explore: What Is Consciousness?]
What Makes Something Right or Wrong?
Most people believe that some actions are morally better than others.
But what makes them so?
Are there objective moral truths, or are ideas about right and wrong ultimately human creations?
One approach judges actions by their consequences. If an action reduces suffering and increases wellbeing, that may count in its favour.
Another argues that some actions are right or wrong because of principles and duties, regardless of their consequences.
Others focus less on individual actions and more on character: what kind of person should we try to become?
Real life makes these differences important. Is it ever acceptable to lie to protect someone? Should one innocent person be harmed to save five others? Do we have moral responsibilities towards animals, future generations or people living on the other side of the world?
Ethics asks us not merely what people do, but what they ought to do — and why.
[Explore: What Makes Something Right or Wrong?]
What Is the Good Life?
Suppose you could design the best possible human life. What would it contain?
Pleasure? Wealth? Friendship? Achievement? Love? Knowledge? Freedom? Service to others?
Ancient Greek philosophers gave this question enormous attention.
Epicurus argued for a life of modest pleasure, friendship and freedom from unnecessary fear. The Stoics emphasised virtue and learning to distinguish between what we can and cannot control. Aristotle believed human flourishing involved developing our abilities and living virtuously within a community.
The question remains just as relevant today.
Modern societies are extraordinarily good at giving us things to pursue, but philosophy asks a more basic question:
Which things are actually worth pursuing?
A successful life and a good life may not necessarily be the same thing.
[Explore: What Is the Good Life?]
Does God Exist?
For much of human history, questions about reality have eventually led to questions about God.
Why does anything exist at all? Does the universe require an explanation beyond itself? Does the apparent order of nature suggest purpose or design?
Philosophers and theologians have developed sophisticated arguments for God’s existence. Others have challenged those arguments or asked how an all-powerful and benevolent God could coexist with apparently pointless suffering.
Science has transformed the discussion by revealing a universe vastly older and larger than earlier generations imagined and by explaining many natural phenomena without requiring supernatural causes.
Yet science does not automatically settle every philosophical question about why there is a universe, whether existence has a purpose, or whether reality extends beyond what science can investigate.
Belief, disbelief and uncertainty therefore continue to coexist.
[Explore: Does God Exist?]
What Makes a Just Society?
Human beings do not live alone. We live in families, communities and societies whose rules profoundly affect our lives.
So what would a fair society look like?
Should everyone have equal opportunities, equal rights or a more equal share of resources? How much freedom should individuals have? When is government justified in restricting it?
The philosopher John Rawls proposed an intriguing thought experiment.
Imagine designing society without knowing who you would become within it. You might be rich or poor, healthy or disabled, powerful or vulnerable.
What rules would you choose if you didn’t know which life would eventually be yours?
Political philosophy examines questions of liberty, equality, justice, rights, property and power.
They are philosophical questions with very practical consequences.
[Explore: What Makes a Just Society?]
What Is the Meaning of Life?
Eventually many philosophical journeys arrive here.
What makes a human life meaningful?
Religion has traditionally provided answers involving God, spiritual development or a larger purpose to existence.
Some philosophers have looked elsewhere.
Existentialists such as Jean-Paul Sartre argued that humans are not born with a predetermined purpose: we create meaning through the lives we choose to lead. Albert Camus confronted the possibility that the universe itself may be indifferent to our desire for meaning.
Others find meaning in relationships, creativity, knowledge, contribution, experience or simply participating fully in life.
Perhaps there is a universal meaning to human existence. Perhaps meaning is something each person creates. Perhaps the question itself needs reconsidering.
Philosophy cannot hand us a universally accepted answer.
But it can help us understand the possibilities — and think more carefully about the answer we give through the way we live.
[Explore: What Is the Meaning of Life?]
The Questions Connect
These ten questions are separated here for convenience, but they quickly become entangled.
Ask what reality is, and you encounter questions about how we can know it.
Ask about knowledge, and you encounter perception and consciousness.
Ask about consciousness, and you encounter the brain, matter and free will.
Ask about free will, and questions of moral responsibility follow.
Ask how we should live, and eventually we encounter happiness, society, God and meaning.
Philosophy is therefore less like a collection of answers and more like a landscape of connected questions.
Nor does the journey end with philosophy.
Questions about reality lead naturally towards physics and cosmology. Questions about consciousness lead towards neuroscience. Questions about morality can take us into psychology, biology, politics and religion. Questions about meaning appear throughout literature, art and the world’s religious traditions.
For thousands of years, human beings have approached the same mysteries from different directions.
The purpose of exploring these questions is not necessarily to find a final answer to each one.
It is to understand the questions better, discover how others have tried to answer them, and examine their ideas, evidence and arguments for ourselves.
But philosophy is not only about learning what other people have thought. Your own ideas matter too.
The great philosophers did not simply accept the answers they inherited. They questioned them, challenged them and developed ideas of their own. We can do the same.
That does not mean every answer is equally convincing. Our ideas should be questioned and tested, just as we question the ideas of others. We may change our minds many times as we learn more.
Over time, however, these questions can help each of us develop our own understanding of reality, knowledge, consciousness, morality, the good life and what gives life meaning.
You do not need to become a philosopher or discover a final answer to everything. Perhaps there are questions that humanity will never completely resolve.
What matters is that we do not simply borrow someone else’s answers without thinking about them for ourselves.
Learn what others have thought. Question it. Compare it with the evidence and your own experience. Be willing to change your mind. And gradually develop your own view of the world.
Philosophy does not have to tell you what to think. It can help you discover what you think – and why.
Want to Keep Exploring?
The ten questions above are only the beginning.
Philosophy soon leads us towards questions that cross the boundaries between philosophy, science, religion and our own experience of being alive.
If you are still curious, continue with 10 More Great Questions of Philosophy:
- What Is Time?
- What Happens When We Die?
- Is There an Afterlife — and What Might Paradise Be Like?
- Why Is the Universe So Big?
- How Did the Universe Begin — and Could Something Come From Nothing?
- Are We Alone in the Universe?
- What Makes You the Same Person Throughout Your Life?
- Do Animals Experience the World Like Us?
- Could a Machine Ever Become Conscious?
- Are There Limits to What Humans Can Understand?
[Explore 10 More Great Questions →]