"Finally there are simple ideas of which no definition can be given; there are also axioms or postulates, or in a word primary principles, which cannot be proved and have no need of proof"

In this quote, Gottfried Leibniz is talking about the presence of easy concepts that can not be specified, as well as essential concepts or axioms that can not be shown but are still vital to understanding the world. Essentially, Leibniz is acknowledging that there are some fundamental concepts that we merely take for granted as reality, without needing to describe or validate them in any way.