You sometimes hear people say that science is just one way of understanding the world, and that science is not really that different from, say, the understanding that comes from literature, faith, or tradition. I come across this in relation to food policy, where people say 'maybe that is what the scientific evidence shows, but I believe that the scientists are wrong'.

I should teach the world that belief is about faith, and science is about evidence. I am sending this survey response by email, and I have confidence that it will arrive - because my computer, my broadband connection, and the internet are based upon scientific understanding. If they were based upon understanding derived from literature, faith, or tradition alone, then I would be right to be doubtful about whether the email would ever get to its destination - just as I would not want to fly in an aircraft that was designed by belief, rather than science.

Scientific explanation is not only based upon replicable observations and experiments, but it is also cumulative. We can be certain that we now have a deeper scientific understanding of the nature of the world around us than did our predecessors, 100 or 200 years ago. In this way, science differs from art. There is no definite way of saying that Pablo Picasso had a deeper understanding of the world than did Michelangelo Buonarroti, but you can say that Francis Crick understood more about the mechanisms of inheritance than did the nineteenth-century Austrian monk Gregor Johann Mendel.

Scientific knowledge is not static, so tomorrow's explanations may differ from today's. But there are certain things that we understand fully enough, to be sure that new observations will not overturn them. We are not going to wake up one day and find that the genetic code has changed, and nor are we going to find that living things can reproduce without a source of energy.

If I were going to explain one specific concept, then it would be Charles Darwin's theory of evolution by natural selection. This concept has the beauty of simplicity, and it explains where we have come from. This concept engenders humility in us, by showing how we are just a small part of the jigsaw of the living world, past and present. This concept engenders awe in us, because it simultaneously explains the staggering diversity of life, and its unity. And this concept engenders hope in us, because only by placing our own actions in the context of the history and diversity of life, can we be judicious guardians of our grandchildren's world.

John Krebs is coauthor of An Introduction to Behavioural Ecology (buy this book from Amazon (UK) or Amazon (USA)).