Aristotelian science conveys understanding by showing the necessary relationship between immediately evident first principles and conclusions about the natural world. To take a trivial example: induction from repeated experience teaches us that all broad-leaved plants are deciduous. We discover that grapevines have broad leaves. We infer that grapevines are deciduous, and thereby we also learn that they lose their leaves in winter because they are broad-leaved (see Aristotle, Post. An. II.16–17).

Aristotelian science explains a subject’s possession of an attribute (the explanandum) by identifying the possession of that attribute with membership in a species, and then citing as explanans the inclusion of that species within a prior genus. In the present example, the property is “losing its leaves in winter,” the species is “grapevines,” and the genus is “broad-leaved plants.” The explanation is then presented in the form of a syllogism. In the first premise an attribute (being deciduous) is predicated of a subject (broad-leaved plant). The second premise introduces a new subject that belongs to the class described by the subject of the first premise, allowing us to conclude that the second subject shares an attribute of the first.

Aristotle describes this demonstration as propter quid science because it explains why grape leaves fall. If the deduction were valid, but its premises were not explanatory, it would count as quia science: knowing a fact without understanding why it obtains (ibid., I.13, 78a22–b3) (see also Chapter 26).

Most popular accounts of the introduction of Aristotle’s natural philosophy credit Arabic civilization with transmitting classical Greek works to the Latin West. By contrast, a few contemporary authors, hostile to Islam, deny any contribution of the Islamic world to scholasticism. Neither claim is credible. As we shall see, although Arabic Aristotelianism did not provide the primary access to Aristotle’s texts themselves, it did make a profound contribution to scholastic natural philosophy.

Confounding this dispute is a misunderstanding of the significance of Arabic-based Aristotle translations. Scholastic authors seldom commented on translations based on the Arabic Aristotle. Almost every major scholastic commentary on Greek philosophical works is based on a direct translation from Greek into Latin, with a few early exceptions. Scholastics evidently recognized that though they were often harder to follow and more obscure than translations from the Arabic Aristotle, Greek-based translations were closer to the original.

So let us look chiefly at the influence of the interpretative tradition of Arabic Aristotelianism on the Latin West, after saying a few words on translations of Arabic texts. We will suggest that though scholastics did not comment on Arabic-based translations of Aristotle, without these translations and more importantly without the interpretative tradition that accompanied them, the scholastic tradition would have been much poorer; indeed, it might never have arisen. After all, James of Venice’s translations had been available since about 1150, but Aristotelian analytics, metaphysics, and natural philosophy began to influence major scholastic authors only when the Michael Scot translations became available around 1225.

Most popular accounts of the introduction of Aristotle’s natural philosophy credit Arabic civilization with transmitting classical Greek works to the Latin West. By contrast, a few contemporary authors, hostile to Islam, deny any contribution of the Islamic world to scholasticism. Neither claim is credible. As we shall see, although Arabic Aristotelianism did not provide the primary access to Aristotle’s texts themselves, it did make a profound contribution to scholastic natural philosophy.

Confounding this dispute is a misunderstanding of the significance of Arabic-based Aristotle translations. Scholastic authors seldom commented on translations based on the Arabic Aristotle. Almost every major scholastic commentary on Greek philosophical works is based on a direct translation from Greek into Latin, with a few early exceptions. Scholastics evidently recognized that though they were often harder to follow and more obscure than translations from the Arabic Aristotle, Greek-based translations were closer to the original.

So let us look chiefly at the influence of the interpretative tradition of Arabic Aristotelianism on the Latin West, after saying a few words on translations of Arabic texts. We will suggest that though scholastics did not comment on Arabic-based translations of Aristotle, without these translations and more importantly without the interpretative tradition that accompanied them, the scholastic tradition would have been much poorer; indeed, it might never have arisen. After all, James of Venice’s translations had been available since about 1150, but Aristotelian analytics, metaphysics, and natural philosophy began to influence major scholastic authors only when the Michael Scot translations became available around 1225.

Aristotelian science conveys understanding by showing the necessary relationship between immediately evident first principles and conclusions about the natural world. To take a trivial example: induction from repeated experience teaches us that all broad-leaved plants are deciduous. We discover that grapevines have broad leaves. We infer that grapevines are deciduous, and thereby we also learn that they lose their leaves in winter because they are broad-leaved (see Aristotle, Post. An. II.16–17).

Aristotelian science explains a subject’s possession of an attribute (the explanandum) by identifying the possession of that attribute with membership in a species, and then citing as explanans the inclusion of that species within a prior genus. In the present example, the property is “losing its leaves in winter,” the species is “grapevines,” and the genus is “broad-leaved plants.” The explanation is then presented in the form of a syllogism. In the first premise an attribute (being deciduous) is predicated of a subject (broad-leaved plant). The second premise introduces a new subject that belongs to the class described by the subject of the first premise, allowing us to conclude that the second subject shares an attribute of the first.

Aristotle describes this demonstration as propter quid science because it explains why grape leaves fall. If the deduction were valid, but its premises were not explanatory, it would count as quia science: knowing a fact without understanding why it obtains (ibid., I.13, 78a22–b3) (see also Chapter 26).

Pelagianism is a heresy first defined in reaction to the views of the monk Pelagius in the fifth century and attacked by Saint Augustine. In the centuries since Pelagius's defeat, theologians have repeatedly stigmatized their opponents as Pelagians. Such disputes typically pit those who emphasize predestination and original sin against those who believe in human free will and human capacity for goodness. But seldom are the arguments in these debates straightforward. Often incredibly refined, they frequently ask us to consider not the human situation as we know it but the situation before the Fall and even the options that obtained (or did not obtain) before humans were created. Not only is Pelagianism a heresy, but so is semi-Pelagianism, and so complicated are the issues involved that advocates of contrary views on relevant issues have both been accused of Pelagianism.