 Atoms were nonetheless used in materialist explanations, which account for physical phenomena such as the combination of different elements to form macroscopic materials. Because we appear to see visible particles of dust, or rays of light shining on glass or mirrors, it seemed reasonable to suppose that interactions too small to perceive produce observed changes in the macroscopic world (Dasgupta 1987). Heat and light were thought to be produced by minute corpuscles entering other bodies. Buddhist atomism regarded atomic properties such as solidity, heat and motion as producing perceptible changes at the macroscopic level (Gangopadhyaya 1980, 13–14). Even with non-material atoms, the question of their occupation of space was considered: Matilal suggests that tangibility may have been regarded as a latent property of the atoms, which emerges like visibility when they cluster (Matilal 1986, 361). Different Buddhist schools disagreed on the answer to these questions.