For the letters are the causes of syllables, and the material is the cause of manufactured things, and fire and earth and all such things are the causes of bodies, and the parts are causes of the whole, and the hypotheses are causes of the conclusion, in the sense that they are that out of which these respectively are made; but of these some are cause as substratum (e.g. the parts), others as essence (the whole, the synthesis, and the form).