Immanuel Kant (1724-1804) was a philosopher. He is a major figure in the history and development of philosophy.
In moral philosophy and ethics, Kant is best known for what’s called “the categorical imperative”. This is most commonly expressed as:
“Act only according to that maxim whereby you can, at the same time, will that it should become a universal law.”—Immanuel Kant, Grounding for the Metaphysic of Morals
The categorical imperative is really a law about laws. It’s a law that says we should govern our decisions only with laws that we would be fine with everyone else also using to govern their decisions. The process of testing if we’d want a law to be universal is called “universalizing”.