Usually when the word "belief" comes up, the first thought is religion, but the general occurrence of beliefs is actually a much broader concept.

Beliefs may be religious, supernatural, philosophical, etc.  In short, we all have beliefs that define how we think the world works and how we should interact with it.  Beliefs bridge the gap between what we "know" and what we "assume" in order to function in the world and make decisions.    

An important point that needs to be understood is that our individual beliefs don't necessarily reflect what we know to be true.  In other words, we may believe many things, personally, that are impossible to prove scientifically, or even that we know are unlikely to be true and yet we continue to believe them anyway.

In some cases, this may be little more than a psychological mechanism to cope with a seemingly random or dangerous world.  In addition there are many instances where we are faced with huge obstacles or problems for which we might be analytically paralyzed if we only considered what we "know to be true1".  

Many people will use varying degrees of assessing information and adjust their "beliefs" accordingly, probably because they "believe" that it is a better philosophical position to be in.  As a result, we expect people that are more scientific to formulate their personal beliefs around scientific knowledge, while religious people will formulate their personal beliefs around their religion.  

It becomes clear that conflict is inevitable when one set of beliefs is used to suggest that another set is untrue.  Note that this doesn't have to change the underlying "facts" or "truth" of a situation, but merely our interpretation of those "facts".

So what's the point?

Humans present a unique problem since they are capable of evaluating abstract information and drawing conclusions giving rise to rational thought. Specifically, humans do not need to directly experience something to be capable of contemplating it.  Whether such a capability exists in other animals is open to interpretation, but it is fair to say that, at the least, humans possess a fairly unique form of rationality.  Ultimately this has given rise to philosophy and the scientific method and the means by which we can measure, assess, and interpret the world around us in a reasonably accurate manner and develop conclusions that allow us to predict future events.  However, for all that science has achieved, it is fundamentally impractical as a means of actually living and surviving in the world.  Many decisions must be made with incomplete knowledge and often our experiences must be capable of drawing conclusions from a single data point.  In short, we must formulate a belief in how things work whether or not they are true.  In other words, our beliefs are what helps the world "make sense" to use at some level.

One could certainly construct an evolutionary scenario where the beliefs that an individual held might directly affect their fitness.  Similarly one could envision how the sharing of such beliefs might give rise to culture and other social bonds.  However, these views may be impossible to prove, but it seems reasonable to conclude that it is likely true that the beliefs held by an individual would be shaped by whether they had consequences to the believer.

This gives rise to an interesting exercise in considering what people believe versus what they profess to believe. In many cases, this can be quite striking because one is forced to reconcile beliefs with "real-world" results.

For example, we tend to "believe" in the laws of gravity.  Even with the most cursory scientific understanding, we all follow those laws because at some fundamental level we appreciate the consequences of violating them.  Therefore we can argue about details regarding gravitation from the scientific perspective, but we are all cautious in elevated places because we "know" what gravity can do.  In short, there are consequences that govern our "belief".  In effect, our belief is unnecessary, but regardless of the facts, we must integrate this knowledge into our belief system as a necessary condition to understanding how the world works.

If we consider other beliefs we may find that there is a wide difference between what an individual professes and their actions.  In this case, we can conclude that such a violation of beliefs is possible because they don't really think that there are consequences.  There may be a rationalization that there are, but at a fundamental psychological level, that viewpoint simply doesn't exist.  Once again, using a simple example.  If an individual believes that cursing or using profanity is wrong, but they periodically engage in it anyway then they are rationalizing a belief.  In other words, they don't actually believe that it is wrong, because in the final analysis they don't believe there are real consequences to it.  While many may argue that this view is unnecessarily restrictive, it illustrates the point.  One would not expect an individual to walk off the roof of a building and then claim that they didn't mean to do that or that they were sorry.  The understanding of what the effects of gravity are clearly permeate the belief system so that the consequences of ignoring it are real.  In the latter case, such consequences are less clear and as a result, the belief isn't nearly as strongly ingrained.

In this latter case, we can find many instances of claiming a particular belief while an individual's actions clearly indicate otherwise.

There is also a third possibility that bears consideration; where a particular belief does bear consequences, even if it isn't as strict as a scientific principle might be. This falls squarely into the domain of culture, where a persistent set of beliefs results in consequences (or protection from consequences) because of the actions of others.  In such cases, it becomes clear that beliefs cannot be changed unless there are consequences associated with the actions perpetrated by those beliefs.  Individuals that are shielded from the consequences of their beliefs can never change them.

If a group of people believe that it is wrong to carry any debt, so they save up money to pay for everything in full.  However, their ability to do so is explicitly dependent on having others that are willing to carry debt (businesses, etc.), so that they can maintain their cash flows, etc in providing the jobs needed.  In this case, one belief is possible only because the majority doesn't share the same view.  Unlike our example of gravity, belief costs nothing and therefore can span many possibilities. In effect, a cultural form of natural selection has been stopped. Consider that it is easy to be a pacifist when one is protected by a well-equipped military. It is easy to oppose vaccines, as long as the majority of people still get them.

So where does that leave us?

As a society, one of the major problems that have to be dealt with is the unrelenting diversity of ideas that people profess to believe.  Whether these ideas are political, religious, sociological, etc., the point is that these will continue to escalate until people have to face the consequences of their choices.  It would seem that one of the most important things we can do as a society is to define, specifically, what we do believe.  In the U.S., some of this occurs with rituals like the Pledge of Allegiance where the intend is to profess a set of "beliefs" regarding the nation similar to what many religions do when they recite their respective creeds.

It is from this perspective of recitation or articulated creeds that we can condense a particular belief system down to its core elements against which all members of the group are expected to adhere.  There is generally nothing in such a creed that defines behaviors, but rather it is used to define the minimal set of tenets to create a unifying belief system.

As a result, it is important to understand that no amount of factual information or scientific data will ever sway someone from their beliefs until such information can be integrated into the existing belief system.  It doesn't matter whether something is true, it only matters whether people believe it to be true.  

So, what do you believe?

1I am being somewhat liberal in my use of the word "true" to signify something that would be considered scientifically accurate or correct, but even in this sense, we can't assume that "truth" is actually so precisely evaluated at an individual level.