Abstract
I argue that both digital and analog information are important in the foundations of quantum physics. If it is possible for information present in one system to become present in others without being erased in the original system I will say that this information can be copied. I argue that copying is important for understanding issues like causality and that all information that can be copied is digital. I then explain that analog information that cannot be copied can be understood in terms of decision theoretic probability. Finally, I argue that these ideas can help explain the second law of thermodynamics. The arrow of time we experience is the knowledge arrow of time -- the present contains more knowledge, that is, useful or explanatory information, than the past. That knowledge is created by evolutionary processes that involve copying, variation and selection and such processes increase entropy.
Alan Forrester