He had a keen interest in modern theory and practice, as well as a deep knowledge of the achievements of his predecessors.

Review of the historic particulars gives body to the generalities of modern theory.

In the modern theory of manifolds, these notions correspond to manifolds with constant, negative and positive curvature, respectively.

In the modern theory the rent was determined by the demand and supply forces in the market like the other factors of production.

However later on the modern theory of rent was developed by the modern economists.