>But still "base load" is no law of nature.

It's a term that means we can guarantee a set amount of power regardless of environmental conditions. Renewables are sensitive to environmental conditions, and we don't have a battery technology to bridge renewable variablity and hence the need for 'base-load'. In that context, 'base load' is a law of nature.

"base load" is also a statistical law of nature. Your consumers might want or need to consume your product regardless of the price. I will run my heating before I freeze to death, and I will thaw a meal before I starve. Somebody will switch on their lights in the dead of night. The hospital will run its MRI when an emergency arises.

All these things are rather randomly occuring things, some correlated, some uncorrelated. All these create a "ground noise" of consumption. All these things lead to a need for baseload power, which can only be removed by switching off the grid.