Ideas, including scientific ideas, do not live suspended in a vacuum, but have relationships across time, and at a point in time, with others, forming out of observed regularities the ‘models’, ‘laws’ and ‘principles’ which are our own creations, shaped as much by what they do not include as by what they do. Adding to their contingency is a simple and very obvious point, the limitation imposed by our sense organs – and our brains. We can’t detect what our sense organs do not permit us to detect: there may be senses that we could have had, but don’t, which would have revealed other aspects of the world to our understanding and which we are incapable of imagining – could we have imagined what it is like to hear, if we had only sight, smell and touch to go on? When aboriginal people say that they can hear, or see, or sense things that we cannot, how do we know they are wrong? And the senses we do have are limited in extent: we can’t hear what bats and bears take for granted in their world. It would be irrational to suppose we are directly aware of more than a little of what exists. Why assume that our cognition is capable of more than a few limited forays into the vastness of reality? Evolution is a process. We know more than mice (though there must also be things they know that we don’t). A more highly evolved creature may one day regard our understanding of the world much as we now view that of the mouse. ‘The wise scientist’, wrote Chargaff, ‘will be aware of the eternal predicament that between him and the world there always is the barrier of the human brain.’15