timelets | Absolutely beautiful

If in an expression, whose content need not be capable of becoming a judgement, a simple or compound sign has one or more occurrences and if we regard that sign as replaceable in all or some of those occurrences by something else (but everywhere by the same thing), then we call the part that remains invariant in the expression a function, and the replaceable part the argument of the function. - Frege.

Now imagine that we are talking about a piece of infrastructure, e.g. a road. Cars are replaceable (transient), the road is not. Nevertheless, there are certain times when the type of cars changes in some interesting way, e.g. from the horse-driven carriage to the automobile. As a result, the road becomes replaceable, i.e. it becomes an argument relative to the car type. From this perspective, a purpose of innovation is to create a type of variable that requires a new type of function. I wonder if this stuff can be formalized.

upd: it follows that the electric car is a smaller innovation, if any, than the self-driving car.