620, on the second Sunday in Advent, in the great
Cathedral of Ulm, he developed the orthodox doctrine of comets in a
sermon, taking up the questions: 1. What are comets? 2. What do they
indicate? 3. What have we to do with their significance? This sermon
marks an epoch. Delivered in that stronghold of German Protestantism
and by a prelate of the highest standing, it was immediately printed,
prefaced by three laudatory poems from different men of note, and sent
forth to drive back the scientific, or, as it was called, the "godless,"
view of comets. The preface shows that Dieterich was sincerely alarmed
by the tendency to regard comets as natural appearances. His text was
taken from the twenty-fifth verse of the twenty-first chapter of St.
Luke: "And there shall be signs in the sun, and in the moon, and in the
stars; and upon the earth distress of nations, with perplexity; the sea
and the waves roaring." As to what comets are, he cites a multitude of
philosophers, and, finding that they differ among themselves, he uses a
form of argument not uncommon from that day to this, declaring that this
difference of opinion proves that there is no solution of the problem
save in revelation, and insisting that comets are "signs especially sent
by the Almighty to warn the earth." An additional proof of this he
finds in the forms of comets. One, he says, took the form of a trumpet;
another, of a spear; another of a goat; another, of a torch; another, of
a sword; another, of an arrow; another, of a sabre; still another, of a
bare arm. From these forms of comets he infers that we may divine their
purpose. As to their creation, he quotes John of Damascus and other
early Church authorities in behalf of the idea that each comet is a
star newly created at the Divine command, out of nothing, and that it
indicates the wrath of God. As to their purpose, having quoted largely
from the Bible and from Luther, he winds up by insisting that, as God
can make nothing in vain, comets must have some distinct object; then,
from Isaiah and Joel among the prophets, from Matthew, Mark, and
Luke among the evangelists, from Origen and John Chrysostom among the
fathers, from Luther and Melanchthon among the Reformers, he draws
various texts more or less conclusive to prove that comets indicate evil
and only evil; and he cites Luther's Advent sermon to the effect that,
though comets may arise in the course of Nature, they are still signs
of evil to mankind. In