He was a theoretical rather than a practical scientist, his contributions to science being in the nature of philosophical reasonings rather than practical demonstrations.

Had he been able to withdraw from public life and devote himself to science alone, as Descartes did, he would undoubtedly have proved himself equally great as a practical worker.

But during the time of his greatest activity in philosophical fields, between the years 1690 and 1716, he was all the time performing extraordinary active duties in entirely foreign fields.
His work may be regarded, perhaps, as doing for Germany in particular what Bacon's did for England and the rest of the world in general.
Only a comparatively small part of his philosophical writings concern us here.

According to his theory of the ultimate elements of the universe, the entire universe is composed of individual centres, or monads.

To these monads he ascribed numberless qualities by which every phase of nature may be accounted.