After a brief description of cognitive sciences, the existence of two mistaken approaches in philosophy of knowledge is emphasized (the one is the historical-scholar and the other is the merely speculative) betting on the approach proper of cognitive sciences, where the subject of cognition is an information processor (following Alan Turing ́s idea) and it can be not only a human but also a machine or an animal. Secondly the cognitive subject is characterized as a physical symbol system (PSS), according to the thesis by Allen Newell and Herbert Simon, and such thesis is commented and illustrated. And finally diverse degrees of cognition in general sense, in animals and in machines, are distinguished, but also it is highlighted the proper or...