As a realist I imagine the world consisting of fundamental things with properties, that are independent of whether they are observed or not. In this essay I try to defend a positivist view, where properties only exist relative to an observer. The observer must not be a human being. I will explore a toy model, where a sheep is in a box and I want to find out what color the sheep has by giving the sheep different flowers to eat. The flowers play the role of an elementary measurement device. I will ask the question: How must the laws look like in order to make such measurement successful? The laws in our model shall be constrained by symmetries. Under such constrains not all properties are observable as we will see. I also discuss the quantum case, where one can either measure the relative color or the relative frequencies of changing colors. The objectivity of such a relative measurement is questioned by Wigner's friend type of measurements. I solve this problem by introducing a physical postulate, that the interaction cannot be switched off. In this case the measurement can only be successful, when the environment is in a special state, where it does not get entangled with sheep-flower system. This means that the possibility of defining physical concepts depends on the environment and finally on the state of the universe. In course of time the cosmological condition change and thus the conditions under which physical concepts can be defined. The idea that physical concepts can change means that, what is fundamental changes with time. I will show that despite of the second law of thermodynamics, the number of possible concepts grow over time and speculate how this is connected to the possibility of free will.
Luca Valeri