It may seem paradoxical that a philosophy of science, especially one which calls itself realist, should start from the premiss that science, like humanity itself, is a historical accident. But can this premiss be seriously questioned, except on some creationist view? The paradox is on the other foot, that of the apparently robust epistemologies which allow us to be certain about our experiences but not about that of which they are experiences (the external world, other minds, or even our own bodies). No serious account of knowledge can begin without the assumption that "to be" is more than "to be perceived". And no theory of science is conceivable without the assumption that what we are pleased to call laws of nature operated in the same way as they do now before humans evolved and a fortiori before they began to do science. It is, when one thinks about it, an odd philosophy of science which ignores such considerations.