All of us to a greater or lesser degree are susceptible to black-and-white thinking. It is a very human trait. The capacity to hold conflicting positions in mind – the grey areas – is difficult work.

This has implications for the ways in which we feel towards and act upon the world, from the particular to the universal, from our personal relationships to or our political beliefs.

Conflict is something central to the experience of being human. Frequently, we want conflicting things at the same time – security and freedom, truth and happiness to name but two – but of course it is impossible. And so we simplify.

But it is painful. So we look for short-cuts to tolerate what feels unmanageable and to ease this pain. This includes black-and-white thinking. It may often be the only way we feel we can manage the uncertainty our conflicts generate.

Psychoanalysis offers compelling accounts for how this develops out of our youngest years (notably Melanie Klein’s concept of paranoid-schizoid thinking). Although it protects the developing infant, it becomes problematic to the later adult.

Much psychoanalytic theory accounts for the existence of human suffering as being related to love and loss and that the job of therapists is to help people acknowledge, experience and bear the realities of life, the pleasures and the heartbreaks. Instead the sources of our suffering are maintained by he lies we tell ourselves. Black-and-white thinking sustains the self-deceptions and eases the anxiety of uncertainty.

The desire for a more certain world is within all of us. And it accounts for much of our psychological or emotional suffering. Coming to terms with this is often central to the work of therapy. Much of the work of the psychotherapist it is to cultivate uncertainty in some way, to come to terms with our ambivalence.

It is often important to try to help clients hold conflicting positions at the same time. This may be about wrestling with conflicting feelings about oneself, one’s future, or sexuality. It could be because of powerfully conflicting feelings towards one’s partner or parent or child.

In its psychoanalytic sense, ambivalence does not mean mixed feelings. Rather, it means opposing feelings. According to psychoanalysis these contradictory feelings enter into everything we do. In Sigmund Freud’s view, we are ambivalent “about anything and everything that matters to us.”

Love and hate – a too simple vocabulary, and so never quite the right names – are a common source. These are the elemental feelings with which we apprehend the world; they are interdependent in the sense that you can’t have one without the other, as well as mutually informing one another. The way we hate people depends on the way we love and vice versa.

Such strong feelings towards the same person can feel intolerable to hold. And so we split off the feelings of hatred. It is a way to manage something that feels unmanageable. It is a way to find greater certainty in an often insecure world. But to do so probably costs us.

Asking of people that they don’t race to one side or another demands much of a client. This way of working jars with much of the world outside of the therapy room. It runs counter to the way the NHS is set up – insofar as the accent these days is heavily weighted towards providing evidence bases that support the work we do.

Of course, the wish and the aim is to help people get ‘better’ by one definition or another. But it is far from simple to add or subtract such changes onto a balance sheet, no matter how loudly that is demanded. The emergence of the audit culture that has grown over the last two decades has left parts of the psychotherapy profession in the midst of a curious tension.

The work of science is to eradicate uncertainty. The progress made in scientific endeavours such as physics or astronomy reflects this progress. But in matters of human emotion the picture is less clear-cut. We cannot apply the same rigours to the person. The demand to measure what matters in the NHS, for a more scientific psychotherapy, rather than a means to progress is in fact a symptom of our need for certainty.

The problem here is that the work of therapy is to allow space for uncertainty. This is incompatible with the demand to fit therapy into the same scientific rationale we would reserve for physicists or astronomers. Humans just cannot be meaningfully measured in the same way – our experience is literally immeasurable, neither reducible nor generalisable.

In matters of the human heart, certainty is an illusion, no matter how much a part of the human endowment it is to desire it. The explanatory force of psychoanalysis helps us understand this paradox. It simultaneously provides some space for the cultivation of ambivalence that – if we can withstand the desire to find certainty – is therapeutic to many of the people therapists see.