Have you ever lain awake at night fretting over how we can be sure of the reality of the external world? This book introduces and explains the problems of knowledge, consciousness, identity, ethics, belief, justice and aesthetics that have engaged the attention of thinkers since the era of the ancient Greeks.

Have you ever lain awake at night fretting over how we can be sure of the reality of the external world? Perhaps we are in fact disembodied brains, floating in vats at the whim of some deranged puppet-master? If so, you are not alone - and what's more, you are in exalted company. For this question and other ones like it have been the stuff of philosophical rumination from Plato to Popper. In a series of accessible and engagingly written essays, "50 Philosophy Ideas You Really Need to Know" introduces and explains the problems of knowledge, consciousness, identity, ethics, belief, justice and aesthetics that have engaged the attention of thinkers from the era of the ancient Greeks to the present day.

Brain in a vat
Categorical imperative
Lifeboat Earth
Plato's cave
Golden rule
Just war
Veil of perception
Acts and omissions
Prisoner's dilemma
Cogito ergo sum
Slippery slopes
Social contract
Reason and experience
Beyond the call of duty
Animals are people too
Tripartite theory of knowledge
Is it bad to be unlucky?
Speciesism
The ghost in the machine
Virtue ethics
Can bad art be good?
What is it like to be a bat?
Forms of argument
Intentional fallacy
Turing Test
Deduction and induction
Nature's watchmaker
Ship of Theseus
Barber paradox
Who lit the blue touchpaper?
Other minds
Gambler's fallacy
The greatest imaginable being
Hume's guillotine
Sorites paradox
Problem of evil
One man's meat
The King of France is bald
Do we really control our destiny?
Divine command theory
Positive and negative freedom
Faith over reason
Boo/hoorah theory
Difference principle
Falsification
Ends and Means
Leviathan
Good science
Experience Machine
Theories of punishment
Ockham's razor