When the geneticist J.S.B. Haldane challenged himself to explain what life is, his initial response was despair:

“I am not going to answer this question. In fact, I doubt if it will ever be possible to give a full answer, because we know what it feels like to be alive, just as we know what redness, or pain, or effort are. So we cannot describe them in terms of anything else.”

Haldane reasoned that it was impossible to fully define life scientifically because humanity has an intuitive knowledge of what things to call living – we can only mimic and give some validity to what we already know to be true. But does Haldane not gift our intuition far too much explanatory power?

Before we discuss what life is, we must examine the origin and veracity of this apparently ironclad intuition. Our intuition, I will argue, is the root of two misleading ideas about life: Vitalism and Essentialism. I want to see whether they can be replaced by a gene-centred view of life – life as the expression of information encoded in the genome. Then I move on to Erwin Schrödinger’s idea that life is special because it appears to defy the universe’s descent into disorder. I will attempt to bring the two ideas together by equating orderliness with information. Finally, I discuss James Lovelock’s Gaia Theory, which posits a living earth, explaining it in terms of Richard Dawkins’ Extended Phenotype. I end, however, with some cautionary words demonstrating why defining life is one of science and philosophy’s most difficult tasks.