The improvement of the telescope was justly regarded as a sine qua non for the advancement of astronomical knowledge.
The only two points on which he departed from the orthodox Lutheran faith of his day were the requirement of regeneration as the sine qua non of the true theologian, and the expectation of the conversion of the Jews and the fall of Papacy as the prelude of the triumph of the church.
The possession of the doctorate is a sine qua non for eligibility to a university chair, and to a lectureship in the university of Paris.
This process is called conceptual synthesis, the possibility of which is a sine qua non for the exchange of information by speech and writing.
An intimate collaboration with England and France was a conditio sine qua non for Czechoslovakia.