I cannot but think that many of those which have been already obtained are of this character.

I cannot but regard it as morally or practically certain that Marcion used our third Gospel; as morally or practically certain that all four Gospels were used in the Clementine Homilies; as morally or practically certain that the existence of three at least out of our four Gospels is implied in the writings of Justin; as probable in a lower degree that the four were used by Basilides; as not really disputable (apart from the presumption afforded by earlier writers) that they were widely used in the interval which separates the writings of Justin from those of Irenaeus.
All of these seem to me to be tolerably clear propositions.

But outside these there seems to be a considerable amount of convergent evidence, the separate items of which are less convincing, but which yet derive a certain force from the mere fact that they are convergent.

In the Apostolic Fathers, for example, there are instances of various kinds, some stronger and some weaker; but the important point to notice is that they confirm each other.

Every new case adds to the total weight of the evidence, and helps to determine the bearing of those which seem ambiguous.
It cannot be too much borne in mind that the evidence with which we have been dealing is cumulative; and as in all other cases of cumulative evidence the subtraction of any single item is of less importance than the addition of a new one.