We said earlier that all matter carries mutual information. So a physical system x that exists now may have mutual information with respect to a physical system that existed in the past, also exists now, and/or will exist in the future. This mutual information is an affordance which can be used by a system to gain value, i.e., move the environment towards a goal state, i.e., serve a purpose. A separate system Z can thus respond in effect to system y (which is distant in time and/or space) by responding in fact to system x.
So, for example, a bacterial food source may generate particular sugar molecules which diffuse away from the source. (The source “causes” sugar molecules which float away). The sugar molecule has mutual information with respect to the source. If a bacterium can hook a mechanism to move to higher concentrations of this sugar molecule it will improve its chances of survival.
But maybe that same food source is toxic to a different bacterium, or is generated by a predator. If this other bacterium can hook a mechanism to move to lower concentrations of the sugar, it will improve its own chances of survival.
So we can say mutual information is an affordance for meaning. The *meaning* of the information is determined by the mechanism which generates the response (output) to the information in the input.
Note we just said that the same system x can have different meanings to different responding systems, depending on the specific responses. It is also true that the same system x can have different mutual information with respect to different responding systems. For example, if I am in a small Japanese village and see a handwritten sign saying “Come in for the best food for miles around!”, I can respond to the mutual information this sign has with restaurants (if I’m hungry), but I can also respond to the mutual information this sign has with native English speakers (if I’m in need of someone who speaks English).
So the bottom line is that “meaning” is determined by a specific response to specific mutual information.