You believe it will rain tomorrow. You believe two plus two equals four. You believe your friend is trustworthy. Belief is the attitude of taking something to be true. It can be conscious and explicit, or implicit and unexamined. It can be based on evidence, habit, authority, or wishful thinking. Philosophers have long debated what kind of state belief is, how it relates to knowledge, and when it is rational.

The standard analysis treats belief as a propositional attitude: a subject believes that some proposition is true. Beliefs come in degrees. You might be certain, fairly confident, or merely inclined to think something is the case. Degrees of belief, or credences, are central to Bayesian epistemology. Beliefs also guide action. If you believe the bridge is safe, you cross it. If you believe it is not, you do not. That connection between belief and behavior is one reason beliefs matter beyond the mind. Philosophers distinguish belief from knowledge, which requires truth and justification. A belief can be true but unjustified, or justified but false.

Types of belief

• Occurrent. Actively held in mind right now.
• Dispositional. Held but not currently conscious.
• Explicit. Clearly formulated.
• Implicit. Operating without awareness.

Belief is also a social phenomenon. Shared beliefs hold communities together and can be resistant to evidence.