Uncertainty is a powerful and nearly all-present state in our lives. Human beings have a wonderful capacity to fill in the gaps – whether it is visual system creating holistic images in our head, or our auditory and language system creating meaning from misheard statements. Our brains are able to fill in the holes and make interpretations that help us to navigate the world. It gives us certainty. But to a large extent this is an illusion. In the same way, our brains fill in the gaps of uncertainty so that we believe that we really know things that generally are unknowable.

Take the future for example. We are able to predict and prognosticate based on previous experiences that we can recall – but although we believe in our own certainties of the what will happen next, the future is fundamentally unknowable. Our certainties are usually based on leaps of faith, that what happened before, will happen again.

Take the people around us – even those who are closest to us. Again, our brain fills in the fundamental gap that exists in all relationships, that we can never truly know, understand and see another person's mind and feelings. There is empathy, but there is no telepathy. Many of the misunderstandings that happen between people come from this sense that we are able to read minds, but we often get it wrong.

What is interesting to me as a psychologist is how each person decides to live with this inevitable state of uncertainty. To a certain extent there is a genetic influence on the differences in individual reactions to not knowing. Some people really do not seem to worry about not knowing, basking in a Buddha-like glow of enlightenment. For some people, uncertainty is a catastrophic state that needs to be conquered and brought into knowable control. Most of us lie somewhere on the spectrum with our reactions to uncertainty influenced by unique combination of personality, situations and events.

Take the different reactions that people have to an event like the 7^th July 2005 London bombings. For example, I was able to travel on public transport the next day paying no heed to the uncertainty of the possibility of being a victim of another atrocity. I am not sure how it was that in this case I did not have any concerns. Perhaps it was because I could rationally evaluate the risks and understand that there was a very low chance of such an event reoccurring. Perhaps also it was my sense of acceptance of my mortality – and my faith in the idea that God decides when I die, so that there is little that I can do about when or how it will occur.

However, there were many people who were indirectly traumatized by the bombings and lost the capacity to deal with the intrinsic uncertainty of whether we will survive traveling on the Underground. Such anxiety can be overwhelming paralyzing. Perhaps these were individuals who had previous experiences that were triggered by the events of the day. Or perhaps individuals who were already nervous about the risks of traveling hundreds of meters beneath the ground.

Anxiety is a normal response to existential uncertainty. We all experience the tension of not knowing sufficient information about a person or situation. When I once treated a woman in her fifties who had not been able to leave her home alone for more than 10 years, it was her imagined fear of what could happen that prevented her from living a normal life. She imagined that she would faint, or fall over, or that people would laugh at her. She imagined being ashamed and embarrassed. These were certainties that her mind had created about what would happen. She had built a seemingly indestructible framework that trapped in her home, but also made her feel safe where it was a controlled and more knowable environment. This was a reaction to a fundamentally uncertain world, in which it was better to be at home rather than risk what might possibly occur outside, irrespective of how likely it was to happen.

Typically, the onset of these kinds of extreme reactions are a reaction to a trigger event or situation. Someone important died suddenly. The house was burgled. A person was involved in a serious car accident. A person fainted because they were dehydrated. The kinds of the events that are difficult to predict and control for.

How we react to such events and our state of uncertainty is often related to our mental health. Fear of the unknown undermines our feelings and desires to be safe. The typical response is to try and create havens of certainty in our lives. Routines. Obligations. Moments to control the situations and the people in our lives. Fixed points of time in our daily lives to eat, watch television, to talk to friends on the phone. Opportunities to occupy and distract from the discomfort of the unknowable reality with in which we live.

This is not about what is a good or bad response. Such judgments are not relevant for most situations. These responses are part of our human existence. There are large number of individuals who experience intense feelings of anxiety – and the time to seek help is when the fears interfere with daily functioning. However, I believe that treatment is not just about extinguishing the anxiety through interventions like cognitive behavioral therapy (even though it has excellent success rates), because for the individuals who are in deep mental distress, the role of therapy should be to understand the states of uncertainty leading to the specific fears, and finding ways to live with not knowing all of the answers all of the time. Therapy in these situations is about learning to live with anxiety and to function without its paralyzing power. Actually, living life is this too: living with our uncertainty and having the faith to trust what happens next. To walk the stepping stones even though we cannot clearly see to where they lead.