We all recognise that, as far as we are living organisms, we are part of nature. Yet, because we perceive ourselves as thinking and knowing subjects, nature appears as the object of knowledge and action, and therefore as something exterior to ourselves. This article questions this conception that spontaneously comes to our minds by retracing it back to Plato’s dualism and his vision of the celestial origin of the soul and its more or less secularized avatars. It suggests that our biological sciences, while having replaced the soul by the brain, still have a lot of work to do in order to free themselves from the frameworks of our philosophical tradition.