One is not rich by what one owns, but more by what one is able to do without with dignity.

Natural science physics contains in itself synthetical judgments a priori, as principles. ... Space then is a necessary representation a priori, which serves for the foundation of all external intuitions.

Thoughts without content are empty, intuitions without concepts are blind.

Upon the solution of this problem, or upon sufficient proof of the impossibility of synthetical knowledge a priori, depends the existence or downfall of metaphysics.

One is not rich by what one owns, but more by what one is able to do without with dignity.

Freedom is that faculty that enlarges the usefulness of all other faculties.

It is precisely in knowing its limits that philosophy consists.