The relationship between belief and knowledge is subtle. Believers in a claim typically say that they know that claim. For instance, those who believe that the Sun is a god will report that they know that the Sun is a god. However, the terms belief and knowledge are used differently by philosophers.
Epistemology is the philosophical study of knowledge and belief. A primary problem for epistemology is exactly what is needed in order for us to have knowledge. In a notion derived from Plato's dialogue Theaetetus, philosophy has traditionally defined knowledge as justified true belief. The relationship between belief and knowledge is that a belief is knowledge if the belief is true, and if the believer has a justification (reasonable and necessarily plausible assertions/evidence/guidance) for believing it is true.
A false belief is not considered to be knowledge, even if it is sincere. A sincere believer in the flat earth theory does not know that the Earth is flat. Similarly, a truth that nobody believes is not knowledge, because in order to be knowledge, there must be some person who knows it.
Later epistemologists have questioned the "justified true belief" definition, and some philosophers have questioned whether "belief" is a useful notion at all.
Mainstream psychology and related disciplines have traditionally treated belief as if it were the simplest form of mental representation and therefore one of the building blocks of conscious thought. Philosophers have tended to be more rigorous in their analysis and much of the work examining the viability of the belief concept stems from philosophical analysis.
The concept of belief presumes a subject (the believer) and an object of belief (the proposition). So like other propositional attitudes, belief implies the existence of mental states and intentionality, both of which are hotly debated topics in the philosophy of mind and whose foundations and relation to brain states are still controversial.
Beliefs are sometimes divided into core beliefs (those which you may be actively thinking about) and dispositional beliefs (those which you may ascribe to but have never previously thought about). For example, if asked 'do you believe tigers wear pink pajamas ?' a person might answer that they do not, despite the fact they may never have thought about this situation before.
That a belief is a mental state has been seen, by some, as contentious. While some philosophers have argued that beliefs are represented in the mind as sentence-like constructs others have gone as far as arguing that there is no consistent or coherent mental representation that underlies our common use of the belief concept and is therefore obsolete and should be rejected.
This has important implications for understanding the neuropsychology and neuroscience of belief. If the concept of belief is incoherent or ultimately indefensible then any attempt to find the underlying neural processes which support it will fail. If the concept of belief does turn out to be useful, then this goal should (in principle) be achievable.
Philosopher Lynne Rudder Baker has outlined four main contemporary approaches to belief in her book Saving Belief:
Belief is most often mandatory for group affiliation or "official" membership. In many cases, people bolster belief in which they are emotionally involved by attempted action to resolve contradictions experienced directly. This is done by creative rationializations to reduce experential dissonance. Human imagination serves as the catalyst for creating, modification and perpetuation of belief.
Hope for a world different or better than the present world allows many people to hold information contradictory to their direct experience as valid. This phenomenon is known as dualism. People often believe merely what they wish to be true, in their mind, no matter how much it stands in direct opposition to experiential life. Belief, as a component of the human mind, is true speculation when assumptions cannot be verified logically reconciled to the external world.
It is impossible for all variations of world belief, in over 6.6 Billion minds, to be simultaneously true. The observation of mutually exclusive belief variation, in various minds, clearly demonstrates the phenomena of diverging human imagination and personal modification. From an individual and/or group viewpoint, the preferred belief is strongly imagined to be the one and only unique "truth," fostering an agenda with perceived rewards and very specific group requirements.
Delusions are defined as beliefs in psychiatric diagnostic criteria (for example in the Diagnostic and Statistical Manual of Mental Disorders). Psychiatrist and historian G. E. Berrios has challenged the view that delusions are genuine beliefs and instead labels them as "empty speech acts", where affected persons are motivated to express false or bizarre belief statements due to an underlying psychological disturbance. However, the majority of mental health professionals and researchers treat delusions as if they were genuine beliefs.
In Lewis Carroll's Through the Looking-Glass, the White Queen says, "Why, sometimes I've believed as many as six impossible things before breakfast." This is often quoted in mockery of the common ability of people to entertain beliefs contrary to fact.
The term limiting belief is used for a belief that inhibits exploration of a wider cognitive space than would otherwise be the case. Examples of limiting beliefs are seen both in animals and people. These may be strongly held beliefs, or held unconsciously, and are often tied in with self-image or perceptions about the world. Everyday examples of limiting beliefs: