Since von Uexküll we know that organisms are cognitive devices, which construct the objects in their Umwelt. Here, expanding on previous work, we show how this construction is carried out through the mechanism of Structural Coupling, which is a process linking an organism and its medium through a never ending sequence of concatenated perception ↺ action loops. Every perception triggers complex patterns of concentration changes of molecules (called internal signals) that select a specific action as the outcome of a Bayesian inference mechanism undergoing continuous Hebbian-like updating. The relation between perception and action is a complex and plastic one, and we put forward that a categorical approach in terms of stochastic mappings and functors would be most commendable to make sense of living systems as cognitive devices. We discuss the updating mechanism of stochastic mappings (conditional probability matrices). Finally, we elaborate on the process of metaphorising, from both a macro and a micro viewpoints. The former sees, from an eagle’s viewpoint, metaphors as functors between inferential categories; the latter sees the emergence of metaphorising as a biological mechanism in the unfolding of the never ending perception ↺ action helix by means of which a living system constructs its Umwelt. We illustrate our viewpoints with the help of various examples in mathematical cognition.