  A further hallmark of Gassendi's atomic and molecular theories is his suggestion, following the views of early atomists (prominently Lucretius), that some atoms are endowed with greater activity than others. The varied activity of such special atoms, or semina rerum, gives rise to a differential dynamism in matter (of purely materialist nature), allowing for special organic structures, as well as growth of crystals. By contrast, neither atoms nor molecules are endowed with powers per se. Nor do atoms bear forces, though certain forces such as gravity can be explained by reference to the behavior of atoms. Chemical forces, on the other hand, have molecular explanations.