In this paper I make the arguments that I see supporting a view of how we can come to know the world we live in. I start from a position in second order cybernetics which turns out to be a Radical Constructivist position. This position is essentially epistemological, and much of this paper is concerned with the act of knowing, crucial when we try to develop an understanding of what we mean when we discuss a field of knowing (knowledge), which is at the root of science. The argument follows a path in which I discuss the essential role of the observer in observing, the creation of constancies between different observings and their exteriorisation as objects which are then represented and used in communication with and between other observers, each unique (and therefore each observing in its own way). This leads to the assertion that the qualities we associate with the objects of our universes are attributes, rather than properties inherent in the objects themselves. At each step in the argument I explore consequences for how we understand the world, in particular through science. I show limitations, new insights and understandings, and reevaluate what we can expect to gain from science. One change is the shift from noun to verb in the consideration of processses – for instance, the study of living rather than life. In this way, I intend to show not only that Radical Constructivism is sensible, but that it does not preclude us having a science. In contrast, it can enrich science by taking on board the sensible. In the process, which science is seen to be the more basic is challenged.