Play is serious. Sometimes it's hard to get this across to people. That's because we think of play as something we do for fun, something we do when we can stop doing the real stuff like work, organising our lives or dealing with necessities. We play in order to not do serious things, we might think. When we come to look more closely at play, we see a whole landscape of human activity in which people are discovering the nature of the world around us, experimenting with what's possible and, when dramatic play is involved, working out relationships and even how we learn that humans are creatures who translate the world through the use of signs, symbols and language (which is itself a symbolic sign system). This makes play sound as if it's some kind of intellectual assault course, but we all know that play is enjoyable and voluntary. If it's not enjoyable and not voluntary, it's best not to call it play! So what is play? I like to think of it as 'trial and error without fear of failure'. We can play with materials - paint, clay, mud, water, stone, wood. We can play with sound with our voices, through hitting, blowing, scraping, vibrating. We can play with language on surfaces, on screens, with our voices. We can play with what we find. We can play with what we (or someone else) has made. We can have an idea where play might lead - or not. For it to work, we must feel free to do it and to carry on doing it. Play is not value-free. It's quite possible for play to be cruel, unfair, vicious or anti-human even. That means that we must ensure that the play we care about and encourage is intertwined with care about equality and freedom, and is itself free of oppression, segregation and persecution. It must be sensitive to unwitting or deliberate exclusion. Play can be solo or co-operative. We might want to think of co-operative play as one of the greatest achievements of the human spirit, the activity that can take us forward to overcome the forces that would destroy us, the activity that can take us forward to overcome the greatest challenges that the human race faces. We use the word play to describe what we do when we play games. Playing games is obviously great fun and we need fun to support our lives. When thinking about play, we might want to distinguish between the games we play in which we play according to rules that have been set by others and the games we play where we invent the rules ourselves. This second kind has particular value because, we discover that we have the power to make and change the world. Does that seem grandiose and overblown? When we look at a child building a sandcastle where the waves are going to wash it away, is that child really learning that they have the power to make and change the world? In a way, yes. They are learning that they can change the sand on the beach, affect how the water washes in, learns how the power of the waves can erode and wash away heaps of sand. This is change and how I as a human am part of change. And this moment is actually not all that different from the moment when Alesandro Volta discovered that what we call electric current could travel through metal, or that Franklin, Crick and Watson discovered the double helix. They all had to play with materials, bringing different elements and ingredients together and observing outcomes. The world has never been the same since the work (play!) of Volta, Franklin, Crick and Watson. This is why those of us who are educators have to help children play with what's around them and what we give them. They will discover the changes they can make, they will make meanings, and they will discover things about themselves, the most important of which is that they can discover possibilities. The world is not a fixed thing devoid of the possibility of change. They are not excluded (or should not be excluded) from the possibility of change. They are (or should be) part of the possibility of change.