Prime matter, therefore, represents the first stage in creation. The next stage is the endowment of this formless matter with corporeality in the abstract, _i. e._, with extension. Then come the specific forms of the four elements, then their compounds through mineral, plant and animal to man. This is not new; we have already met with it in Gabirol and Ibn Zaddik. Nor is the following significant statement altogether new, though no one before Ibn Daud expressed it so clearly and so definitely. It is that the above analysis of natural objects into matter, universal body, the elements, and so on, is not a physical division but a logical. It does not mean that there was a time when prime matter actually existed as such before it received the form of corporeality, and then there existed actually an absolute body of pure extension until it received the four elements. No, nothing has existence _in actu_ which has not individuality, including not only form, but also accidents. The above analysis is theoretical, and the order of priority is logical not real. In reality only the complete compound of matter and form (the individual) exists. Allusion to matter and form is also found in the Bible in Jeremiah (18, 1ff.), "Arise and go down to the potter's house.... Then I went down to the potter's house, and, behold, he wrought his work on the wheels.... Behold as the clay in the potter's hand...."[233] The next important topic analyzed by Ibn Daud is that of motion. This is of especial importance to Ibn Daud because upon it he bases a new proof of the existence of God, not heretofore found in the works of any of his predecessors. It is taken from Aristotle's Physics, probably from Avicenna's treatises on the subject, is then adopted by Maimonides, and through his example no doubt is made use of by Thomas Aquinas, the great Christian Scholastic of the thirteenth century, who gives it the most prominent place in his "Summa Contra Gentiles." Ibn Daud does not give Aristotle's general definition of motion as the "actualization of the potential qua potential" (_cf._ above, p. xxxii), but his other remarks concerning it imply it. Motion, he says, is applied first to movement in place, and is then transferred to any change which is gradual, such as quantitative or qualitative change. Sudden change is not called motion. As the four elements have all the same matter and yet possess different motions--earth and water moving downward, fire and air upward--it cannot be the matter which is the cause of their motions. It must therefore be the forms, which are different in different things.