What is security?

'Security' is a powerful word. Governments sometimes use it to end a discussion: 'this is a matter of national security, so no questions'. But in a democracy, citizens need to understand what security means, because decisions taken in its name affect them.

At its most basic, security means freedom from threats. A life without any threat at all is impossible, though. Missing a bus is a problem, not a security issue.

So security is about threats to 'core values': the most important things a country or a person holds dear. That raises hard questions:

• Whose core values: the country's as a whole, the government's, or ordinary people's?
• How intense must a threat be before we call it a security threat?

The answer the chapter gives: security covers only extremely dangerous threats, threats that could damage core values so badly that they could not be repaired. Not every problem qualifies.

Ideas of security are not fixed. They have changed over time and differ between societies: what a small island state fears is not what a big power fears.

The many ideas fall into two groups:

• Traditional security: mainly about the state and military threats to it (next two lessons).
• Non-traditional security: about people and threats like disease, poverty, terrorism and climate change (lesson 4).