George Spencer Brown was a somewhat mysterious figure. One can choose whether to regard him as a genius, a boozer, a rather esoteric mathematician by trade, a poet or a provider of footnotes for Niklas Luhmann. Maybe he is a bit of each.
In any event, where he has inspired systems theory and philosophy, is with his attempt to make time relevant in mathematics. Usually, in this, the passage of time, the movement of a point on an axis of time, only arises as a subordinate phenomenon. He, on the other hand, begins with time, whereby he starts his design of mathematics with the famous sentence “Make a distinction”. To do this, one needs time: One has to produce the distinction (maybe draw a circle), one must describe the one side as well as the other (inside/outside), and one can then utilise this distinction – by using time! – as it takes time to move from inside to outside.
As trivial as this may seem, it is, nevertheless, a paradigm shift in mathematics. Even if, as a non-mathematician, one cannot pass a judgement about the consequences of this for mathematics and logic and how well founded it is, it nevertheless remains a way of thinking which has proved itself very powerful, especially for the development of theory within systems theory. Central concepts, such as reflexiveness, increase in complexity, paradoxes, open futures and pasts, amongst many others, are inspired by G. S. Brown.