Abstraction is a prerequisite of perception. We can only ever focus a small excerpt of our surrounds. We apprehend the rest only vaguely or not at all. The relation between what we see in focus and what we see blurred could be compared to that between a simple line drawing and the world as a whole in all its complexity. We constantly produce abstractions in order to concentrate on specific things. This phenomenon can also be used when we try to understand something. When we draw or scribble we capture on paper views of what concerns us and can concentrate on the details that matter to us at that moment. Everything else remains invisible. This results in images at once abstract and specific, which in the process of reflection may only make sense for a short time. Charles Sanders Peirce (1839–1914) referred to such drawings as “moving pictures of thought”, meaning that they are in constant motion like the thoughts to which they are in exchange.